tag:theconversation.com,2011:/ca/topics/red-blood-cells-40451/articlesRed blood cells – The Conversation2023-09-18T12:19:14Ztag:theconversation.com,2011:article/2124342023-09-18T12:19:14Z2023-09-18T12:19:14ZSickle cell disease can be deadly, and the persistent health inequities facing Black Americans worsen the problem<figure><img src="https://images.theconversation.com/files/547633/original/file-20230911-15-6egffi.jpg?ixlib=rb-1.1.0&rect=60%2C0%2C6720%2C4436&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">More than 93% of Americans hospitalized for sickle cell disease are Black. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/african-man-with-oxygen-support-in-hospital-room-royalty-free-image/1312641893?phrase=Black+person+in+hospital&adppopup=true">SeventyFour/iStock via Getty Images Plus</a></span></figcaption></figure><p>The pain from a heart attack is so bad that – if you can imagine – it can feel like an elephant sitting on you. Patients with sickle cell disease, a genetic condition affecting the red blood cells, report that this kind of pain begins before their first birthday and continues intermittently for a lifetime.</p>
<p>Too often these people receive inadequate help managing their pain, a critical health disparity that persists <a href="https://doi.org/10.1001/archinte.1910.00050330050003">113 years after sickle cell disease was identified</a>. </p>
<p>I am a <a href="https://nursing.ufl.edu/profile/wilkie-diana/">professor of nursing</a>, and my research focuses on managing pain in sickle cell and cancer patients. I also am a member of the Lancet Haematology Commission, which recently published a report showing paths forward toward worldwide health <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">equity for patients with sickle cell disease</a>. </p>
<p>Here are some key challenges and opportunities I have seen for helping sickle cell patients cope with this disease.</p>
<h2>The biology of sickle cell disease</h2>
<p><a href="https://www.cdc.gov/ncbddd/sicklecell/facts.html">Sickle cell disease</a> results from genetics – more specifically, the inheritance of faulty hemoglobin genes, one from each parent. </p>
<p><a href="https://www.mountsinai.org/health-library/tests/hemoglobin">Hemoglobin</a> is the iron-rich part of the red blood cell that allows it to carry oxygen from the lungs to all cells in the body. </p>
<p>But sickle hemoglobin – known as hemoglobin “S,” which is the <a href="https://www.cdc.gov/ncbddd/sicklecell/facts.html#">faulty hemoglobin gene</a> – causes the typically round red blood cell to be crescent-shaped, like a banana or a sickle. These sickle cells, which are sticky and very stiff, get trapped in tiny blood vessels and block blood flow and oxygen delivery to the body’s organs and tissues. </p>
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<figcaption><span class="caption">In sickle cell disease, a single genetic mutation alters the shape of hemoglobin. Starting from less than a year old, patients with the disease experience repeated episodes of stabbing pain.</span></figcaption>
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<p>Not only does this cause pain, it also <a href="https://www.cdc.gov/ncbddd/sicklecell/complications.html">affects those organs and tissues</a> near the blockages, including the eyes, kidneys, bones, lungs, heart and the brain, where damage can be so severe it causes a stroke. Patients may also have infections, particularly pneumonia and blood infections. Some men with the disease may have painful erections. </p>
<p>For patients with the disease, half of their red blood cells can be sickle cells.
Typical red blood cells live for about four months, while sickle cells live for three weeks or less.</p>
<p>This means that patients with sickle cell disease do not have enough cells able to carry oxygen to meet their body’s needs. In the meantime, the slow replacement of cells causes anemia, which is characterized by a <a href="https://theconversation.com/anemia-afflicts-nearly-1-in-4-people-worldwide-but-there-are-practical-strategies-for-reducing-it-212177">reduced number of red blood cells and extreme fatigue</a>.</p>
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<a href="https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of sickle-shaped cells in the bloodstream surrounded by normal round red blood cells and white blood cells." src="https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547970/original/file-20230913-21-15pk1s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">For patients with sickle cell disease, about half of their blood cells have the characteristic sickle shape, preventing proper blood flow and oxygen from getting to organs and tissues.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/sickle-cell-anaemia-illustration-royalty-free-illustration/1128675054?phrase=sickle+cell+disease&adppopup=true">Mark Garlick/Science Photo Library via Getty Images</a></span>
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<h2>A reduced life expectancy</h2>
<p>Worldwide, nearly <a href="https://doi.org/10.1016/S2352-3026(23)00118-7">8 million people live with sickle cell disease</a>. In the U.S., 100,000 people have the disease. Three million more Americans carry the sickle cell gene, a condition known as <a href="https://www.cdc.gov/ncbddd/sicklecell/traits.html">sickle cell trait</a>, because they inherited the gene from only one parent. </p>
<p>Most ancestors of those with sickle cell trait likely came from Africa, South Asia or Mediterranean regions where it <a href="https://doi.org/10.1111/j.1365-2141.2008.07085.x">protected the population against malaria</a>. When the malaria parasite infects the red blood cells of someone with sickle cell trait, the infected cell sickles, and then the <a href="https://doi.org/10.1111/ecoj.12433">body’s immune system removes</a> it. </p>
<p>Sickle cell disease is particularly devastating to families in lower-income countries, where many children with the condition <a href="https://doi.org/10.1080/00034983.1979.11687243">die before their fifth birthday</a>. In contrast, few American children with sickle cell disease who have access to medical care die during childhood. </p>
<p>Still, life expectancy for those with sickle cell disease in the U.S., even with public health insurance, is <a href="https://doi.org/10.1053/j.semperi.2015.03.008">almost 24 years less</a> than the general population – <a href="https://doi.org/10.1182/bloodadvances.2022009202">52.6 years compared with 76.1 years</a>. </p>
<h2>Health inequities</h2>
<p>Of the nearly 75,000 Americans hospitalized for sickle cell disease from 2016 to 2018, <a href="https://doi.org/10.1111/ejh.13936">more than 93% were Black</a>. A century <a href="https://doi.org/10.1001/archinte.1910.00050330050003">after sickle cell disease was identified</a>, <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">glaring health inequities</a> in its diagnosis, treatment, cures and research about it persist. Although anyone with a faulty hemoglobin gene can pass the disease to their children, in the U.S. it is most common in those of African descent. Structural racism and stigma compound the inequities. </p>
<p>People with the disease frequently visit the emergency room and are hospitalized for pain control. Sometimes, these acute pain episodes are excruciating <a href="https://doi.org/10.1016/j.pmn.2012.10.007">and last up to 11 days</a>. But often, doctors and nurses <a href="https://doi.org/10.1097/NCC.0000000000000750">do not believe their complaints</a> and requests for strong medications to stop the pain. Instead, they may suspect drug-seeking behavior, deny them pain medicines and label them drug addicts.</p>
<p>These negative views stigmatize those with the disease and contribute to the stress of living with the illness. Patients report feeling “less than human” when providers <a href="https://www.myamericannurse.com/palliative-care-may-reduce-pain-disparities-in-sickle-cell-disease/#">ignore or discount their pain complaints</a>. </p>
<p>As a result, many patients with sickle cell disease avoid going to the emergency room and do so only when they have exhausted every treatment available at home. They wait, as the pain intensifies to 8, 9 or 10 on a 0-10 scale. By remaining at home, not only is the patient enduring unremitting pain, they are also delaying treatment for organ and tissue damage caused by the disease. </p>
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<figcaption><span class="caption">A bone marrow transplant is one of the possible cures for sickle cell disease.</span></figcaption>
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<h2>Treatments, cures and hope</h2>
<p>In my view, better dialogue between patients, families and providers is critical. A communications tool called the <a href="https://doi.org/10.1097/PTS.0b013e2181660c06">situation, background, assessment, recommendation communication method</a> could help patients when <a href="https://doi.org/10.3390/ijerph192113817">interacting with providers</a> about their pain and, over time, reduce stigma associated with the illness. </p>
<p>Some adults may have been tested for sickle cell trait as newborns but were not told or do not remember whether they have it. These adults are unaware of their risk for having a baby with the disease. This is why <a href="https://qualifying4choices.ahc.ufl.edu/qualifying/">testing, along with genetic counseling, is also critical</a>.</p>
<p>Today in the U.S., <a href="https://www.aafp.org/pubs/afp/issues/2008/0501/p1300.html">all newborn babies are now tested</a> for both sickle cell disease and sickle cell trait. This test helps to spot and treat the disease early, before the baby has symptoms or serious problems, and reduces one structural racism contributor because every baby is tested.</p>
<p>Red blood cell transfusions are an <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">important and lifesaving treatment</a> for sickle cell disease. But there are challenges to transfusion therapy, including difficulty getting into a vein, iron overload, reactions to the transfusion and the time commitment and travel expenses.</p>
<p>Treatment with daily oral hydroxyurea is the <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">standard of care for prevention of pain</a> in both children and adults with sickle cell. This drug increases fetal hemoglobin, which reduces red blood cell sickling. There are also other drugs available that can reduce red blood cell sickling. </p>
<p>One therapy that can cure sickle cell disease is <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">hematopoietic stem cell transplantation</a>. This is the transfer of stem cells capable of making normal blood cells to replace the sickle cells. The stem cells are transplanted to the patient from a well-matched sibling, which limits who can get them.</p>
<p>Since 1984, 1,200 hematopoietic stem cell transplantation cases <a href="https://www.ncbi.nlm.nih.gov/books/NBK538515/">have been reported</a>. However, the treatment can have serious toxicities, fatal complications, effects on fertility and significant financial costs that must be weighed against the severity of the disease. </p>
<p>Other cures are gene therapies to repair the faulty hemoglobin gene so that it <a href="https://doi.org/10.1016/S2352-3026(23)00096-0">no longer makes sickle red blood cells</a>. But gene therapy is not yet a standard cure. </p>
<p>Neither of these curative treatments alters the genes in the ovum or sperm, so the patient’s future children are still at risk of inheriting the disease. </p>
<p>A future with health equity for sickle cell disease is possible, but only when pain is controlled and treatments have fewer complications and can be made affordable everywhere.</p><img src="https://counter.theconversation.com/content/212434/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Diana J. Wilkie receives funding from the National Institutes of Health. She collaborates with many scientists and clinicians focused on sickle cell disease. She was a member of the Lancet Haematology Commission on Sickle Cell Disease.</span></em></p>Many people with sickle cell disease don’t receive adequate treatment to ease their pain and are subjected to racial discrimination and stigmatization.Diana J. Wilkie, Professor of Nursing, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2121772023-09-08T12:25:59Z2023-09-08T12:25:59ZAnemia afflicts nearly 1 in 4 people worldwide, but there are practical strategies for reducing it<figure><img src="https://images.theconversation.com/files/546721/original/file-20230906-33614-a4o8yh.jpg?ixlib=rb-1.1.0&rect=15%2C7%2C5126%2C3484&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anemia symptoms include shortness of breath, dizziness and fatigue.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/doctor-holding-blood-in-test-tube-royalty-free-image/1180192054?phrase=anemia&adppopup=true">Peter Dazeley/The Image Bank via Getty Images</a></span></figcaption></figure><p>Anemia is a major health problem, with <a href="https://doi.org/10.1016/S2352-3026(23)00160-6">nearly 2 billion people</a> affected globally. It afflicts more people worldwide than low back pain or diabetes – or even anxiety and depression combined. </p>
<p>Despite this, investments in reducing anemia have failed to substantially reduce the massive burden of anemia globally over the last few decades.</p>
<p>People <a href="https://www.ncbi.nlm.nih.gov/books/NBK499994/">become anemic</a> when their blood lacks enough healthy red blood cells to carry oxygen throughout the body. This decreased oxygen delivery causes many of the most <a href="https://www.nhlbi.nih.gov/health/anemia/symptoms">common symptoms of anemia</a>, including fatigue, shortness of breath, lightheadedness, difficulty concentrating and challenges with work and daily life tasks. </p>
<p>In addition to its direct health effects, anemia can <a href="https://doi.org/10.1111/nyas.14105">inhibit brain development and fine motor skills</a> in children and heighten the <a href="https://doi.org/10.3390/jcm10122556">risk of stroke</a>, <a href="https://doi.org/10.1681/ASN.2005030226">cardiovascular disease</a>, <a href="https://doi.org/10.1212/WNL.0000000000008003">dementia</a> and other chronic illnesses in older adults. <a href="https://doi.org/10.1111/nyas.14093">Anemia during pregnancy</a> can lead to increased rates of anxiety and depression, early labor, postpartum hemorrhage, stillbirth and low birth weight. Infections for both mother and baby are also more likely when the mother is anemic.</p>
<p>We are <a href="https://scholar.google.com/citations?user=LbtdQcsAAAAJ&hl=en">global</a> <a href="https://scholar.google.com/citations?user=0kfiPK8AAAAJ&hl=en">health</a> <a href="https://www.healthdata.org/about/people/nicholas-kassebaum">researchers</a> with expertise in epidemiological modeling of anemia alongside other maternal, neonatal and nutritional disorders. </p>
<p>Our work is part of the <a href="https://www.healthdata.org/research-analysis/gbd">Global Burden of Disease Study</a>, a large research study comprehensively estimating health loss due to hundreds of diseases, injuries and risk factors around the globe. Through our analysis, we have produced annual estimates of anemia prevalence by underlying cause for 204 countries and territories, by age and sex, from 1990 to the present. We have collected thousands of data points across hundreds of sources to produce the most comprehensive picture of anemia burden.</p>
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<figcaption><span class="caption">Anemia is often measured by the amount of hemoglobin – an oxygen-carrying protein within red blood cells – that a person has in their blood.</span></figcaption>
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<h2>Anemia is a widespread problem</h2>
<p>Anemia is diagnosed by a simple blood test and can be caused by a number of underlying conditions. </p>
<p>Decreases in healthy red blood cells can occur due to excessive loss of existing red blood cells, such as through bleeding or destruction by the body’s immune system. Anemia can also occur due to decreased production of new red blood cells or changes in the normal structure or lifespan of red blood cells that make them less effective.</p>
<p>Globally, anemia is the third-largest cause of disability: Our recent study found that <a href="https://doi.org/10.1016/S2352-3026(23)00160-6">nearly 1 in 4 people has anemia</a>. This burden is concentrated among children younger than 5 years and adolescent girls and women, one-third of whom are anemic. Anemia rates are particularly high in sub-Saharan Africa and South Asia, where we estimated that 40% – or two out of every five people – have anemia.</p>
<p>Reductions in anemia rates have been slow and uneven, dropping from 28% to 24% globally from 1990 to 2021. Adult males have fared better, with young children and adolescent girls and women – who bear the highest burden of anemia – showing the least progress. On the positive side, there has been a shift toward milder forms of anemia, which result in much less disability compared to severe anemia.</p>
<h2>Reducing anemia means tackling underlying causes</h2>
<p>Substantially reducing anemia globally is complicated by its many underlying causes. Dietary iron deficiency is the <a href="https://doi.org/10.1016/S0140-6736(15)60865-0">most common cause</a> across the globe. But other important drivers of anemia include blood disorders such as <a href="https://www.cdc.gov/ncbddd/sicklecell/index.html#">sickle cell disease</a> or <a href="https://www.cdc.gov/ncbddd/thalassemia/facts.html">thalassemias</a>, infectious diseases like <a href="https://theconversation.com/locally-transmitted-malaria-in-the-us-could-be-a-harbinger-of-rising-disease-risk-in-a-warming-climate-5-questions-answered-208726">malaria</a> and <a href="https://theconversation.com/parasitic-infections-hit-the-health-of-low-income-black-communities-where-states-have-neglected-sewage-systems-205616">hookworm</a>, gynecologic and obstetric conditions, <a href="https://theconversation.com/what-is-inflammation-two-immunologists-explain-how-the-body-responds-to-everything-from-stings-to-vaccination-and-why-it-sometimes-goes-wrong-193503">inflammation</a> and chronic diseases. </p>
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<a href="https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three-dimensional illustration of human artery anatomy, showing normal red blood cells and sickle-shaped blood cells flowing away from the heart." src="https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=478&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=478&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547067/original/file-20230907-9809-nfpk9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=478&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sickle cell disease – characterized by crescent or sickle-shaped red blood cells that can block blood flow to the rest of the body – is a well-recognized cause of anemia.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/sickle-cell-cardiovascular-royalty-free-image/1130415446?phrase=sickle+cell+disease&adppopup=true">wildpixel/iStock via Getty Images</a></span>
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<p>Anemia in adolescent and adult women often occurs due to loss of blood from menstruation and increased needs for blood for the developing baby during pregnancy. Much of the anemia burden in this group is <a href="https://doi.org/10.3390/nu13082745">likely related to</a> <a href="https://theconversation.com/the-us-lacks-adequate-education-around-puberty-and-menstruation-for-young-people-an-expert-on-menstrual-health-explains-187501">lack of menstrual education</a>, inadequate options for effectively managing menstrual problems in those who have them, and unmet needs for family planning services. These are also important drivers among transgender men and nonbinary people who menstruate. </p>
<p>Young children <a href="https://doi.org/10.1016/j.jpeds.2015.07.014">have increased requirements</a> for iron as their bodies grow, and malnutrition is a common cause of anemia in this group globally.</p>
<p>Iron supplementation has historically been the primary form of treatment and prevention of anemia. This includes large-scale addition of iron to foods such as flour, rice or milk, as well as providing oral iron tablets and intravenous iron, depending on the context and severity. </p>
<p>Some research has suggested that less than half of people with anemia will <a href="https://doi.org/10.1111/nyas.14175">fully respond to supplemental iron</a> if the underlying causes of iron deficiency remain untreated. For example, cells in our bodies <a href="https://doi.org/10.1016/j.beha.2004.08.020">sequester iron</a> as part of the immune response to some infections. Supplementing with iron without treating the underlying infection will do little to solve the iron deficiency in the long run, and it <a href="https://doi.org/10.1016/S0140-6736(06)67962-2">may even be harmful</a>.</p>
<p>Additional interventions include <a href="https://www.cdc.gov/hiv/risk/art/index.html">HIV treatment and prevention</a>, with <a href="https://theconversation.com/long-acting-injectable-prep-is-a-big-step-forward-in-hiv-prevention-190225">pre-exposure prophylaxis</a> and <a href="https://www.cdc.gov/hiv/basics/livingwithhiv/treatment.html">anti-retroviral therapy</a>. Preventing initial infection with HIV or suppressing the effects of the virus once infected will reduce the anemia burden related to HIV/AIDS.</p>
<p>Other strategies include malaria control methods, such as insecticide-treated bed nets and vaccination, and monitoring and prevention of chronic illnesses such as <a href="https://www.cdc.gov/kidneydisease/basics.html#">chronic kidney disease</a> and <a href="https://www.niehs.nih.gov/health/topics/conditions/inflammation/index.cfm">inflammatory conditions</a>. In combination with a robust supplementation program, these interventions could meaningfully reduce the global burden of anemia.</p>
<p>Anemia makes it hard for nearly 2 billion people worldwide to learn in school, perform at work and take care of their families. We hope our findings will allow for more comprehensive intervention and treatment plans, especially for the most vulnerable – adolescent and adult women, children and the elderly.</p><img src="https://counter.theconversation.com/content/212177/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Kassebaum receives funding from the Bill & Melinda Gates Foundation. </span></em></p><p class="fine-print"><em><span>Theresa A McHugh and William Gardner do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Among young children, adolescents and adult women, anemia strikes 1 in 3 globally. Most cases are driven by dietary iron deficiency, red blood cell disorders and untreated tropical diseases.William Gardner, Researcher in Neonatal and Child Health at the Institute for Health Metrics and Evaluation, University of WashingtonNicholas Kassebaum, Adjunct Professor in Health Metrics Sciences and Professor of Anesthesiology and Pain Medicine, University of WashingtonTheresa A McHugh, Researcher and Scientific Writer at the Institute for Health Metrics and Evaluation, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1745812022-01-31T13:00:06Z2022-01-31T13:00:06ZWhy do we bleed? A hematologist explains how the body prevents blood loss after injury<figure><img src="https://images.theconversation.com/files/441609/original/file-20220119-25-1kfjasu.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2039%2C1471&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The body starts plugging up wounds as quickly as it can to prevent blood loss and infection.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/finger-with-a-bead-of-blood-royalty-free-image/545247995"> Jonathan Knowles/Stone via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<blockquote>
<p><strong>Why do we bleed? – Michael, age 9, Seattle, Washington</strong></p>
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<p>“Ouch!” I cried out, looking down at where my family’s puppy, Hercules, had just bitten me. Two tiny dots of red started to bloom where he had sunk his canine teeth into my finger.</p>
<p>“Bad dog,” I said to him. He looked up at me sheepishly. “Well, I guess I’m a bad human for putting my finger near your mouth,” I admitted. He wagged his tail and licked my arm.</p>
<p>I put pressure on my finger until the bleeding stopped. Three weeks later the area had healed, and we had taught Hercules to heel, too!</p>
<p><a href="https://scholar.google.com/citations?user=n2R5Ow4AAAAJ&hl=en">I am a doctor</a> who specializes in <a href="https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/hematology">hematology</a> – the study of blood. Here, I’ll share with you how blood travels through the body, how we bleed and, more importantly, how we stop bleeding.</p>
<h2>What’s inside blood?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing normal blood composition" src="https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=731&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=731&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=731&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=919&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=919&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441790/original/file-20220120-9299-1mqm0vp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=919&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Blood is a mix of red and white blood cells, platelets and plasma.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:1901_Composition_of_Blood.jpg">OpenStax College/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>The blood in our bodies is a <a href="https://training.seer.cancer.gov/leukemia/anatomy/composition.html">complex fluid</a>. It contains red blood cells, which bring oxygen to our body’s tissues; white blood cells, our body’s infection-fighting army; and platelets, which clump together to help stop bleeding. A special protein called <a href="https://kidshealth.org/en/kids/blood.html">hemoglobin</a> in red blood cells is what gives our blood its beautiful red color.</p>
<p>The yellowy, liquid portion of blood is called <a href="https://www.redcrossblood.org/donate-blood/dlp/plasma-information.html">plasma</a>. Most of it – <a href="https://www.britannica.com/science/plasma-biology">over 90% of it</a> – is water, but the remaining portion contains molecules that help our blood clot and stop bleeding.</p>
<h2>Where does blood live and where does it travel?</h2>
<p>The <a href="https://emedicine.medscape.com/article/1968326-overview">bone marrow</a>, located in the center of our bones, is the factory that makes the cells circulating in our bloodstream.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/1Qfmkd6C8u8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Bone marrow transplants are given to patients with blood cancers like leukemia and lymphoma.</span></figcaption>
</figure>
<p>Once blood cells are made, they move into <a href="https://www.ncbi.nlm.nih.gov/books/NBK279250/">blood vessels</a> – rubbery tubes that form roads traveling through our entire body. Veins are the vessels that carry blood to the heart, while arteries carry blood to the rest of the body. The biggest vessels can be the width of a garden hose, while the smallest can be tinier than a human hair. Blood <a href="https://www.pbs.org/wgbh/nova/heart/heartfacts.html">travels 12,000 miles</a> through the vessels of an adult every single day!</p>
<p>The heart is the powerful engine that pushes blood through those tubes to deliver oxygen and nutrients to our organs and skin. First, the right side of the heart pumps the blood into the lungs, which contains oxygen from the air we breathe. Here, the <a href="https://doi.org/10.1002/cphy.c080113">hemoglobin</a> in red blood cells grabs oxygen and take it back to the heart. </p>
<p>The left side of the heart then pumps that oxygen-rich blood to the rest of the body. After red blood cells drop off their oxygen cargo, they are pumped back to the right side of the heart to get more oxygen and repeat their tour of the body again. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of human circulatory system" src="https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441612/original/file-20220119-15-h5wzp6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Blood delivers oxygen to the body by flowing through the circulatory system using a system of vessels.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/flat-design-circulatory-system-infographic-royalty-free-illustration/1286314341">Nadezhda Ivanova/iStock via Getty Images Plus</a></span>
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<h2>Why do we bleed?</h2>
<p>The skin forms a protective layer over our bodies. When that layer is damaged, the blood vessels immediately underneath it are torn, allowing blood to leak out. </p>
<p>A small cut tears just the small vessels near the skin, and only a tiny amount of blood drips out. A deep cut might tear larger vessels and cause more bleeding. When we bang an arm or a leg, tearing the smaller vessels without damaging our skin, blood collects under the unbroken skin to form a <a href="https://medlineplus.gov/bruises.html">bruise</a>.</p>
<p>Because the heart is still pumping blood throughout the body, more blood will continue to leak out until the damage is patched up. To stop the leaking, a torn blood vessel releases chemicals that <a href="https://doi.org/10.1161/01.ATV.0000130465.23430.74">activate proteins</a> that clump together and form a plug to <a href="https://medlineplus.gov/ency/imagepages/19462.htm">fill the hole</a>. This seals up the blood vessel and prevents more blood from getting out. You’ve seen the results of this on your skin before: the scab that forms on top of a scrape or cut.</p>
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<a href="https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing process of platelet and fibrin clumping to close a wound to a blood vessel." src="https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=652&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=652&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=652&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=819&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=819&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441613/original/file-20220119-23-1hvgipb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=819&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Platelets and proteins called fibrin plug the hole in a blood vessel to stop bleeding.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/hemostasis-basic-steps-of-wound-healing-royalty-free-illustration/1179785857">ttsz/iStock via Getty Images Plus</a></span>
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<p>Applying pressure to a wound helps stop bleeding because it pushes the walls of the vessel together to slow the flow of blood. This helps form a clot to plug the tear, starting the healing process.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/174581/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mikkael A. Sekeres does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Blood plays a vital role in keeping us alive, from delivering oxygen to the body’s organs to fighting off infections.Mikkael A. Sekeres, Professor of Medicine and Chief, Division of Hematology, Sylvester Cancer Center, University of MiamiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/961172018-11-02T04:57:56Z2018-11-02T04:57:56ZHow our red blood cells keep evolving to fight malaria<figure><img src="https://images.theconversation.com/files/243188/original/file-20181031-76411-hdymx7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Even without drugs, nets or an understanding of what caused malaria, human bodies were still fighting against the parasite – and winning.</span> <span class="attribution"><span class="source">from shutterstock.com</span></span></figcaption></figure><p>Ever since humans first evolved from our primitive ancestors, we have been locked in a battle with our greatest infectious foe – malaria. This life-threatening disease, caused by the Plasmodium parasite and transmitted through mosquito bites, <a href="http://www.who.int/en/news-room/fact-sheets/detail/malaria">kills one child</a> every two minutes. There were an estimated 216 million cases of malaria in 91 countries (most in sub-Saharan Africa) in <a href="https://www.who.int/malaria/publications/world-malaria-report-2017/en/">2016</a>, which is 5 million more than the previous year. </p>
<p>For most of history, humans lived without antimalarial drugs, bed nets or even the basic understanding of how malaria is caused. But still our bodies fought against it. In the intense human-malaria war, one way humans could survive would be to make ourselves less hospitable to the pathogen. And that’s exactly what happened.</p>
<p>Over thousands of years, randomly occurring differences in our genetic code that inadvertently reduced malarial risk and provided a survival advantage have been “selected” – meaning these genetic differences become more prominent in the population. Today, human populations in specific parts of the world carry heavy genetic marks from our ancient war with malaria. And it is the red blood cell (erythrocyte) that mostly bears the scars.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-115-years-of-data-tells-us-about-africas-battle-with-malaria-past-and-present-85482">What 115 years of data tells us about Africa's battle with malaria past and present</a>
</strong>
</em>
</p>
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<h2>The red blood cell</h2>
<p>The erythrocyte is a remarkable cell. It ships oxygen, bound to iron in the red haemoglobin molecule, from the lungs and heart to every tissue in the body. Its unique shape – a biconcave disc – allows it to deform and reshape itself. This helps it squeeze into the smallest of blood vessels to deliver its payload of oxygen. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243189/original/file-20181031-76390-g37vpl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The red blood cell’s unique shape helps it get into difficult places to deliver oxygen.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>But red cells can also be homes to malaria parasites. These parasites grow, replicate and then burst from the cells during an infection, damaging not just the infected red cell but also uninfected bystanders. Damaged red cells are removed from circulation and the reduction causes anaemia (low levels of haemoglobin), which makes people feel weak, tired and lethargic. In severe cases, it can kill.</p>
<p>Malaria has provoked humans to modify the red cell to protect itself from infection. Almost every part of the red cell – from its membrane to the globin genes that confer its role in oxygen transport – harbour common genetic changes in a desperate effort to help our species survive the onslaught of malaria. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-whats-actually-in-our-blood-75066">Explainer: what's actually in our blood?</a>
</strong>
</em>
</p>
<hr>
<h2>Genetic changes and sickle cells</h2>
<p>Perhaps the most important changes have happened to the haemoglobin molecule itself. Haemoglobin comprises two key components: haem, which contains iron and binds oxygen, and globin, which is a quartet of two copies each of two components – alpha and beta globin. In every part of the world where malaria is now or has previously been common, humans have evolved changes in the globin genes.</p>
<p>A single change in the beta globin sequence and hence protein structure causes what is known as sickle haemoglobin (HbS). Carriers of HbS (who have one mutant and one normal copy of the gene) have little difference in their blood counts and no symptoms. But they have about a <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(12)70055-5/fulltext">30% reduction in susceptibility</a> to malaria – a pretty heavy protection.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243197/original/file-20181031-76411-1jq40xm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A sickle-like shape prevents the red blood cell from doing its job.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>This gives an enormous advantage for children living in an endemic malaria setting. All cases of HbS are caused by an identical genetic change occurring under high pressure of malaria infection. It appears to have arisen spontaneously at least five times over our evolution in different regions in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3728122/">Africa, India and the Middle East</a>. </p>
<p>Proportions of populations in these places, or those descended from them, still commonly carry the mutant gene. About 10% of the African American population are <a href="https://www.cdc.gov/ncbddd/sicklecell/data.html">carriers of the sickle cell trait</a>. Individuals of Indian, Eastern Mediterranean, Caribbean and Middle Eastern descent can also be affected.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=708&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=708&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=708&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=889&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=889&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243599/original/file-20181102-83638-167arft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=889&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Laboratory slide of sickle cell disease, showing several sickle-shaped blood cells.</span>
<span class="attribution"><span class="source">Dr Salvatore Fiorenza/Dr Giles Kelsey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While those who carry a single copy of HbS don’t have symptoms, carriers of two copies of HbS (which means they have no normal copy of beta globin) can suffer a life-altering genetic condition known as sickle cell anaemia. </p>
<p>Their red blood cells become susceptible to changing to a rigid, sickle-like shape. This prevents blood from flowing and can result in frequent, unpredictable <a href="https://ghr.nlm.nih.gov/condition/sickle-cell-disease">attacks</a> of pain, organ damage and even stroke.</p>
<p>The severity of sickle cell disease is reduced for those fortunate to have increased levels of fetal haemoglobin persisting into adulthood. Amazingly, to help defend people with sickle cell disease from the severe consequences of this condition, an otherwise silent genetic condition – <a href="https://www.omim.org/entry/141749#7">hereditary persistence of fetal haemoglobin</a> – has arisen in populations where sickle cell disease is common.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-one-day-science-may-cure-sickle-cell-anaemia-28153">Explainer: one day science may cure sickle cell anaemia</a>
</strong>
</em>
</p>
<hr>
<h2>Thalassaemia</h2>
<p>Other populations have evolved different changes in their globin genes to try to defend themselves against malaria. Deletions of part, or all, of the alpha or beta globin genes result in people carrying the blood disease alpha or beta thalassaemia.</p>
<p>Carriers are usually completely healthy, except for a symptomless anaemia detectable only when a blood test is performed. But these conditions are increasingly recognised as perhaps one of <a href="https://www.sciencedirect.com/science/article/abs/pii/S1079979617304497">main causes of mild anaemia</a> in parts of Asia, the Pacific and the Middle East. </p>
<p>Just like the sickle cell mutation, this protects against invasion by a malaria parasite. But people who carry two deleted copies of their beta globin gene <a href="https://tascsa.net.au/what-is-thalassaemia-sickle-cell-anaemia/">suffer severe anaemia</a> and may require lifelong blood transfusions to survive. </p>
<p>The consequences of deletions of alpha globin genes are more variable, but infants with deletion of all copies of their alpha globin genes usually have such severe anaemia <em>in utero</em> that they do <a href="https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=163596">not even survive to birth</a>. </p>
<h2>The red cell membrane</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=694&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=694&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=694&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=872&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=872&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243607/original/file-20181102-83644-1rl7hap.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=872&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A laboratory slide showing a red blood cell containing a malaria parasite (purple ring with a dark purple dot).</span>
<span class="attribution"><span class="source">Dr Salvatore Fiorenza/Dr Giles Kelsey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Then there are evolutionary changes to the Duffy protein. This is a receptor found on the red cell membrane, which is also the protein through which the parasite <em>Plasmodium vivax</em> – the second-most-common cause of malaria – enters the cell. </p>
<p>Almost all the populations in West Africa and well over half of all Africans have <a href="https://www.ncbi.nlm.nih.gov/pubmed/17607593">inactivated the expression of this gene</a> in their red blood cells. This means they have red cells that are resistant to <em>P. vivax</em> invasion.</p>
<p>Other changes to the red cell membrane can also protect against malaria. People living in Papua New Guinea and other parts of the Pacific may have red blood cells that resemble Nutri-Grain breakfast cereal, with a horizontal stripe or two. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=470&fit=crop&dpr=1 600w, https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=470&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=470&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=590&fit=crop&dpr=1 754w, https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=590&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/243605/original/file-20181102-83626-17pgzo8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=590&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Laboratory slide of Southeast Asian ovalocytosis, showing Nutri-Grain-like cells with one or two horizontal bands.</span>
<span class="attribution"><span class="source">Dr Salvatore Fiorenza/Dr Giles Kelsey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This often asymptomatic condition is called Southeast Asian ovalocytosis. It occurs due to a mutation of a red blood cell protein (which determines the structure of the cell), which makes the rest of the red cell scaffold more rigid than normal. This renders the individual resistant to malarial parasite invasion and protects them from infection. </p>
<p>New mechanisms evolved by our red cells to protect us from malaria are still being discovered. Iron deficiency anaemia, which affects hundreds of millions of (mainly) children and women around the world, has been thought to be mainly due to inadequate nutritional intake of iron. </p>
<p>But now it appears to protect red blood cells from malaria parasite invasion. Many studies show iron-deficient children have a <a href="https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciy791/5096852">reduced risk of developing malaria</a>. This means improving iron status (for example, through iron supplementation) could predispose children to risk of <a href="https://www.bmj.com/content/362/bmj.k3165.abstract">infection</a>.</p>
<h2>Malaria is fighting back</h2>
<p>In recent years, human evolution has been complemented by scientific breakthroughs. Effective antimalarial drugs, insecticide-treated bed nets that protect sleeping children from mosquitoes, and rapid tests that can diagnose a case of malaria in a few minutes without the need for a trained microscopist have all helped. </p>
<p>But there is evidence the parasite (and its mosquito host) are evolving to win back the advantage. For example, almost all of a strain of <em>Plasmodium falciparum</em> parasites are resistant to one of the first anti-malarials, <a href="https://www.cdc.gov/malaria/malaria_worldwide/reduction/drug_resistance.html">Chloroquine</a>. </p>
<p>Now, multi-drug-resistant parasites rule in parts of Southeast Asia, particularly near the Thai-Burma border. Here, resistance to important antimalarials such as mefloquine and, increasingly, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4996140/">artermisinin</a>, which is the backbone of effective therapy, has emerged.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/weekly-dose-mefloquine-an-antimalarial-drug-made-to-win-wars-55566">Weekly Dose: mefloquine, an antimalarial drug made to win wars</a>
</strong>
</em>
</p>
<hr>
<p>Even more ingeniously, parasites have started learning to hide from rapid diagnostic testing by <a href="https://www.who.int/malaria/publications/atoz/information-note-hrp2-based-rdt/en/">deleting the HRP2</a> protein these tests rely on to detect them. In this way, they allow the parasite to continue to live (and spread) undetected in an untreated host.</p>
<p>And the malaria-spreading Anopheles mosquito, found throughout the world where malaria is endemic, is learning to bite humans for its blood meal <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388271/">earlier in the evening</a>, rather than later at night when people are sleeping, to subvert the protection offered by bed nets.</p>
<p>So the battle isn’t over. Our oldest foe remains with us and continues to be a formidable opponent.</p><img src="https://counter.theconversation.com/content/96117/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sant-Rayn Pasricha receives funding from the National Health and Medical Research Council. </span></em></p>Today, human populations carry heavy genetic marks from the war with malaria. And it is the red blood cell (erythrocyte) that mostly bears the scars.Sant-Rayn Pasricha, Laboratory Head, Population Health and Immunity/ Infection and Immunity, Walter and Eliza Hall InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/831432018-01-15T19:06:43Z2018-01-15T19:06:43ZI’ve always wondered: why do our veins look blue when our blood is red?<figure><img src="https://images.theconversation.com/files/201249/original/file-20180108-83559-cyw7s1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our veins only appear blue through the skin, they're actually red. </span> <span class="attribution"><span class="source">from www.shutterstock.com</span></span></figcaption></figure><p><em>This is an article from I’ve Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au</em></p>
<hr>
<p><strong>I’ve always wondered why our veins are blue, when blood is red? - Alexandra, 28, Melbourne</strong></p>
<p>Blood is red, and a surgeon will tell you our veins too are red, they only look blue when we see them through our skin. But why?</p>
<p>The answer depends on a number of things, including how your eyes perceive colour, how light behaves when it contacts your body, and the special properties of blood.</p>
<p>Light travels in peaks and troughs. And the distance between each trough is called a wavelength. Different colours of light have waves of different lengths. Red light has a long wavelength (about 700 nanometres), violet light has a short wavelength (about 400 nanometres), and the rest of the spectrum is spread out in between.</p>
<p><img width="100%" src="https://media.giphy.com/media/12Yf5CuhUpjDG0/giphy.gif"></p>
<p>We see something as a particular colour when light of that colour hits our eyes –either directly from a light source or reflected from a surface.</p>
<p>To understand what colour our veins appear, we need to think about what happens to different wavelengths of light when they hit our skin, how far they can travel through our skin, and what happens when they get to our veins.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-rainbows-round-81187">Curious Kids: Why are rainbows round?</a>
</strong>
</em>
</p>
<hr>
<p>The light that hits our skin during the day is basically white, which is a mixture of all the visible wavelengths. But to explain why our veins look blue, we will look at just the red and blue ends of the spectrum.</p>
<p>Red light has a long wavelength – and this means it is less likely to be deflected by materials and can more easily travel through. Red light can travel pretty well through the skin and body tissues, reaching up to 5-10mm below the skin, which is where many veins are.</p>
<p>When it gets to the veins, the red light is absorbed by the haemoglobin (the protein that makes our blood red). You can demonstrate this to yourself. If you shine a red light on your arm, you will see some red light reflected back, and dark lines where the veins are, as the red light is absorbed by the haemoglobin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-whats-actually-in-our-blood-75066">Explainer: what's actually in our blood?</a>
</strong>
</em>
</p>
<hr>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NS68ePykav0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Red light makes our veins appear as dark lines.</span></figcaption>
</figure>
<p>This phenomenon is actually used to help medical personnel find veins to take blood – by shining red, and sometimes infrared (which is an even longer wavelength) light on the arm.</p>
<p>Blue light has a short wavelength (about 475 nanometres), and is scattered or deflected much more easily than red light. Because it’s easily scattered it doesn’t penetrate so far into the skin (only a fraction of a millimetre). When blue light hits the skin, it’s mostly deflected back. </p>
<p>If you shine a blue light on your skin, what you see is basically blue skin, and veins are hard to find. You may have seen blue light used in spaces such as public bathrooms to discourage intravenous drug use.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201103/original/file-20180108-83547-pr38y0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Blue lighting is used in some spaces to discourage intravenous drug use as it makes it harder to find veins.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Tampere_station_WC.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>So, now imagine the red light and the blue light shining on your skin at once, as happens when you are under white light. You will have a mixture of red, blue and other colours reflected back where there are no veins. Where there are veins, you will see relatively less red, and relatively more blue compared to the surrounding skin.</p>
<p>This means your veins will appear blue compared to the rest of your skin.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201297/original/file-20180109-83559-19kt3yi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Interestingly, the effect varies depending on how deep the vein is, and also on <a href="https://www.ncbi.nlm.nih.gov/pubmed/21085227">how thick the vein is</a>. Very narrow veins close to the surface, such as the capillary bed, will not appear blue.</p>
<p>Blue veins appear more prominent in very pale skinned people, and this may have given rise to the expression “blue blood” for European nobility in the 19th century. These people were untanned from manual labour, and so their veins appeared blue under the skin.</p>
<hr>
<p><em>With thanks to Science Writer at the Australian Red Cross Blood Service Alison Gould.</em></p>
<hr>
<p><em>* Email your question to alwayswondered@theconversation.edu.au
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* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #alwayswondered, or
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<p class="fine-print"><em><span>David Irving does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Blood is red, but our veins are blue. Or are they?David Irving, Adjunct Professor, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/900672018-01-15T16:06:50Z2018-01-15T16:06:50ZRevealed: adult leukaemia can be caused by gene implicated in breast cancer and obesity<figure><img src="https://images.theconversation.com/files/201962/original/file-20180115-101505-1tj72tw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">AML under the microscope. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/blood-smear-under-microscopy-showing-on-550330186?src=1RRsQj8cvHJjbcMN_p5BAw-1-37">Medtech THAI STUDIO LAB 249</a></span></figcaption></figure><p>When people think of leukaemia, they usually think of blood cancers that affect children. These mostly come under the category of acute lymphoblastic leukaemia – or ALL – and are different to the group of blood cancers which predominantly affect adults over the age of 60, known as acute myeloid leukaemia (AML). </p>
<p>AML accounts for about 90% of all leukaemias in adults, though it affects some children too. With <a href="http://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/leukaemia-aml/incidence#heading-One">some 3,000</a> new cases each year in the UK alone, it is tougher to treat than ALL. </p>
<p>Where advances in ALL treatment have raised survival rates to <a href="https://www.stjude.org/disease/acute-lymphoblastic-leukemia-all.html">around 90%</a> over the past several decades, the rates for surviving the less well researched AML are <a href="https://www.healthline.com/health/acute-myeloid-leukemia-survival-rates-outlook">more like</a> 65%. Older adults respond least well to treatment, with only 5% of over-65s surviving more than five years. </p>
<p>I am therefore pleased to report a promising discovery. Work in which I have been involved has shown that a particular gene can play a critical role in the development of the disease. This could be the precursor to a breakthrough that could be life-saving for patients. </p>
<h2>Cells and treatments</h2>
<p>Your bone marrow contains stem cells which divide and differentiate into red blood cells and the main groups of white blood cells – myeloid cells, neutrophils and lymphocytes. Normally this happens in a very controlled manner, ensuring you have all the red blood cells needed to carry oxygen around your body, and all the white blood cells needed to fight off infections. </p>
<p>In AML too many immature myeloid cells are produced too quickly by the bone marrow. They are mutant cells which don’t mature, meaning they fail to defend against infection. </p>
<p>For this reason, early signs of AML include flu-like symptoms, aches and pains in the joints, and rapid weight loss. As the abnormal cells build up inside the bone marrow or the blood they grow and divide aggressively. Left untreated, AML patients can have only weeks to live. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=913&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=913&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=913&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1148&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1148&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201963/original/file-20180115-101505-e9kfw7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1148&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bone marrow transplant.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bone-marrow-transplant-operation-786989008?src=V3Gd5UZImFRTdR5V6xaclg-1-7">El-Roi</a></span>
</figcaption>
</figure>
<p>Patients are normally treated by two stages of chemotherapy over a few months: an induction phase which reduces the number of cancer cells to undetectable levels, then a consolidation phase to kill any cancerous cells hiding in the body. Patients often also receive a bone marrow transplant, effectively giving them a new immune system. </p>
<p>Treating AML is complicated by patients generally being older, since they tolerate the intensive chemotherapy less well. In many cases, they receive some treatment and end up only living a few months. Better understanding the mutations to develop more targeted and less harsh treatments looks like the key to improving survival. </p>
<h2>Step forward, PTPN1</h2>
<p>A number of mutations are associated with AML, and often occur in combinations. It’s these mixtures of mutations that are thought to cause the <a href="https://www.cancer.org/cancer/acute-myeloid-leukemia/detection-diagnosis-staging/how-classified.html">complex subtypes</a> of cancers within the AML group. One common mutation is called <a href="http://www.cytocell.com/probes/23-del20q-deletion">Del20q</a>. It involves the deletion of part of <a href="https://ghr.nlm.nih.gov/chromosome/20">chromosome 20</a>, one of the 23 pairs of chromosomes most humans have in all their cells. </p>
<p>It has <a href="http://www.bloodjournal.org/content/bloodjournal/82/11/3424.full.pdf?sso-checked=true">long been suspected</a> that genes on this part of the chromosome may function, either individually or together, to suppress cancer. Until recently, however, researchers have found it hard to say which genes are responsible. </p>
<p>One candidate is known as PTPN1, or protein tyrosine phosphatase, non-receptor type 1. First discovered in the late 1980s and linked to metabolic function, it is more famously known for its roles in <a href="https://www.ncbi.nlm.nih.gov/pubmed/27465552">breast cancer</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/25120222">type 2 diabetes</a>. Its location on chromosome 20 has long made specialists suspect it could also be involved in AML. </p>
<p>It was <a href="https://www.nature.com/articles/leu201731">shown recently</a> that when you switch off the equivalent gene in mice, it leads to what are known as <a href="https://www.cancersupportcommunity.org/myeloproliferative-neoplasms">myeloproliferative neoplasm</a>, which is the wider family of blood cancers of which AML is a member. In <a href="http://cancerres.aacrjournals.org/content/early/2017/11/09/0008-5472.CAN-17-0946">our new study</a>, we have taken this a step forward: we have shown that if you delete this gene in older mice, it specifically gives rise to AML – and in a similar way to how the disease develops in older humans. </p>
<p>The previous study showed that PTPN1 is deleted from chromosome 20 in the cells of patients in around 17% of AML cases, which raises questions about the remaining majority of cases. We were able to show that deleting the mouse equivalent of PTPN1 activates a molecule called STAT3, which is important to regulating cell growth and division. </p>
<p>If a patient has too much STAT3, it leads to the generation of too many immature myeloid cells – that hallmark of AML I mentioned earlier. This is potentially a very useful finding for further studies into the genetics behind the disease: in the two other most common mutations linked to AML, which relate to a protein called JAK2 and a receptor called FLT-3, STAT3 is also over-activated. In all, STAT3 is relevant to maybe three quarters of all AML cases. Uncovering exactly how they relate looks critical to developing an eventual cure. </p>
<h2>The future</h2>
<p>In short, we’re closing in on understanding the links between PTPN1, STAT3 and AML. A few years from now, as the cost of genome sequencing falls, it will become a question of identifying which combination of mutations has affected a patient and prescribing a treatment accordingly. </p>
<p>This treatment will probably be more bespoke chemotherapy for patients that can tolerate it, and perhaps gene editing using tools such as <a href="https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/questions-and-answers-about-crispr">CRISPR</a> for those that cannot. Doctors would edit the correct versions of genes like PTPN1 back into the patient’s bone marrow, potentially restoring normal function and negating the often difficult search for a compatible bone marrow donor. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/201964/original/file-20180115-101498-q5v593.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New edition.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bone-marrow-transplant-operation-786989008?src=V3Gd5UZImFRTdR5V6xaclg-1-7">vchal</a></span>
</figcaption>
</figure>
<p>There is much research still to be done. We need to understand what PTPN1 is doing in healthy myeloid cells to grasp which processes are disturbed when it becomes deleted. The other big question is whether instead of getting deleted, PTPN1 sometimes more subtly mutates and how this relates to AML. Besides this, there are many other genes on the Del20q deletion that we need to better understand, too. </p>
<p>In the meantime, showing that removing PTPN1 leads to AML is an important piece of the puzzle. It brings the day closer when survival rates for AML make the same climb that we have seen in other kinds of leukaemia, and hopefully even beyond.</p><img src="https://counter.theconversation.com/content/90067/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samantha Le Sommer does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Improvements in survival rates for acute myeloid leukaemia have failed to keep pace with other leukaemias. That may be about to change.Samantha Le Sommer, Postdoctoral Researcher, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/750662017-07-24T20:12:06Z2017-07-24T20:12:06ZExplainer: what’s actually in our blood?<figure><img src="https://images.theconversation.com/files/170731/original/file-20170524-5786-oxlpch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our blood has more functions than we probably realise - all vital for life. </span> <span class="attribution"><span class="source">from www.shutterstock.com.au</span></span></figcaption></figure><p><em>This week we’re running a series in collaboration with the Australian Red Cross Blood Service looking at blood: what it actually does, why we need it, and what happens when something goes wrong with the fluid that gives us life. Read other articles in the series <a href="https://theconversation.com/au/topics/blood-series-39533">here</a>.</em></p>
<hr>
<p>Blood is vitally important for our body. As it’s pumped around our body through veins and arteries, it transports oxygen from our lungs to all of the other organs, tissues and cells that need it. Blood also removes waste products from our organs and tissues, taking them to the liver and kidneys, where they’re removed from the body.</p>
<p>About 45% of our blood consists of different types of cells and the other 55% is plasma, a pale yellow fluid. Blood transports nutrients, hormones, proteins, vitamins and minerals around our body, suspended in the plasma. They provide energy to our cells and also signal for growth and tissue repair. The average adult has about five litres of blood.</p>
<p>The different types of blood cells include red blood cells, platelets, and white blood cells, and these are produced in the bone marrow, in the centre of our bones.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=384&fit=crop&dpr=1 754w, https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=384&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/177639/original/file-20170710-587-zksmvf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=384&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
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<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Red blood cells</h2>
<p>Red blood cells are essential for transporting oxygen around the body. Red cells are very small, donut-shaped cells with <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3678251/">an average lifespan of 120 days</a> within the body. They contain a protein called haemoglobin, which contains iron and binds very strongly to oxygen, giving blood its red colour. </p>
<p>Red cells are flexible and able to squeeze through even the tiniest of our blood vessels, called capillaries, to deliver oxygen to all of the cells in our body. When the red cells reach our organs and tissues, haemoglobin releases the oxygen.</p>
<h2>Platelets</h2>
<p>Platelets are even smaller than red blood cells. In fact, they are tiny fragments of another much larger type of cell, called a megakaryocyte, which is located in the bone marrow. Platelets are formed by budding off from the megakaryocyte. Platelets have an average lifespan of eight to 10 days within the body, so they are constantly being produced. When body tissue is damaged, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4925965/">chemicals are released that attract</a> platelets. </p>
<p>Platelets clump together and stick to the damaged tissue, which starts to form a clot to stop bleeding. Many of the proteins that help the clot to form are contained in plasma. Platelets also release growth factors that help with tissue healing.</p>
<hr>
<p><a href="https://theconversation.com/from-animal-experiments-to-saving-lives-a-history-of-blood-transfusions-80391"><em>Infographic - From animal experiments to saving lives: a history of blood transfusions</em></a></p>
<hr>
<h2>White blood cells</h2>
<p>Blood also carries white blood cells, which are an essential part of our immune system. Some white cells are able to kill micro-organisms by engulfing and ingesting them. Other types of white cells, called lymphocytes, release antibodies that help to fight infection.</p>
<p>Blood cells don’t act alone; they work together for normal body function. For example, when we cut our skin, platelets help plug the cut to stop it bleeding, plasma delivers nutrients and clotting proteins, white cells help to prevent the cut from becoming infected, and red cells deliver oxygen to help keep the skin tissue healthy.</p>
<h2>Blood transfusions</h2>
<p>Sometimes patients who are having surgery, cancer treatment or when they are seriously injured need a blood transfusion. This is usually because they have lost a lot of platelets, red cells or plasma, or because their cancer treatment has killed many of their blood cells.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/5ZMuPciBVy8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The journey of blood.</span></figcaption>
</figure>
<p>In Australia, blood is donated by voluntary blood donors at the <a href="http://www.donateblood.com.au/">Australian Red Cross Blood Service</a>. A typical whole blood donation is just over 450 mL, and it takes around ten minutes to collect. Every time a donation is made, the donor is screened for infectious diseases such as hepatitis and HIV, so these aren’t transferred to the patient receiving the blood. </p>
<p>After donation, the blood is separated into its different parts: platelets, red cells and plasma, which are known as blood components. White cells are removed because they can cause problems in patients who receive them. Once the blood has been separated, it’s stored until it’s needed by hospitals. The red blood cells are stored in a refrigerator and the plasma is frozen. The red cells can be stored for six weeks, and the plasma can be stored for up to a year. Platelets can only be stored for five days. When a hospital needs blood it’s packed into special blood shippers, and transported to the hospital blood bank to be transfused.</p>
<hr>
<p><em><strong>Read other articles in the series:</strong></em></p>
<p><em><a href="https://theconversation.com/essays-on-blood-why-do-we-actually-have-it-75064">Essays on blood: why do we actually have it?</a></em></p>
<p><em><a href="http://theconversation.com/from-animal-experiments-to-saving-lives-a-history-of-blood-transfusions-80391">From animal experiments to saving lives: a history of blood transfusions</a></em></p><img src="https://counter.theconversation.com/content/75066/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Denese Marks receives funding from the Australian and New Zealand Society of Blood Transfusion, Defence Health Foundation and MacoPharma Pty Ltd. Australian governments fund the Australian Red Cross Blood Service for the provision of blood, blood products and services to the Australian community.</span></em></p>Blood transports nutrients, hormones, proteins, vitamins and minerals around our body.Denese Marks, Adjunct Associate Professor, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/750642017-07-23T20:10:04Z2017-07-23T20:10:04ZEssays on blood: why do we actually have it?<figure><img src="https://images.theconversation.com/files/178776/original/file-20170719-13561-1ibysp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We know blood is vital for life, do we know why?</span> <span class="attribution"><span class="source">Illuminations: Blood Equality by Jordan Eagles (USA) Image credit: David Meanix and courtesy of artist as part of Science Gallery Melbourne’s BLOOD exhibition</span></span></figcaption></figure><p><em>This week we’re running a series in collaboration with the Australian Red Cross Blood Service looking at blood: what it actually does, why we need it, and what happens when something goes wrong with the fluid that gives us life. Read other articles in the series <a href="https://theconversation.com/au/topics/blood-series-39533">here</a>.</em></p>
<hr>
<p>Just as a village can’t grow into a city without some form of transport (road, rail or river) that provides necessary interconnections for it to flourish, living things are limited in the size they can reach unless they have some form of circulatory system to transport nutrients and remove waste.</p>
<p>Single celled organisms such as bacteria and fungi, and some multicellular creatures such as sponges, corals and flatworms, simply absorb the nutrients they need and get rid of their waste using a passive process known as diffusion (which is much like soaking in and draining out).</p>
<p>More complex animals have developed some kind of circulatory system. A variety of different systems and pumps (hearts) have developed, but they all have a few things in common. These include something to carry oxygen around their bodies, a fluid of some sort, and some “plumbing” – in humans (and a number of other species) the fluid is called blood and the plumbing is our arteries, veins and capillaries. The oxygen carrier is haemoglobin.</p>
<p>Depending on the organism and where it has adapted to live, its oxygen carrier can come in different forms, often giving its “blood” different colours. Spiders, crustaceans, octopuses and squid use haemocyanin, which is based on copper and gives them blue blood. This carrier works well in low oxygen environments and in the cold. </p>
<p>Segmented worms and some leeches use an iron based carrier called chlorocruorin, which can appear either green or red, depending on its chemical environment. Vertebrates, including humans, use haemoglobin, which makes their blood red.</p>
<p>A truly special case is the <a href="https://blogs.scientificamerican.com/brainwaves/how-the-antarctic-icefish-lost-its-red-blood-cells-but-survived-anyway/">Antarctic icefish</a>, which lost its haemoglobin long ago as a result of a presumably random mutation. It has adapted though, and now survives by transporting oxygen that is simply dissolved in its blood. This is possible thanks to the cold conditions it lives in.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=526&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=526&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176694/original/file-20170704-7743-1u6unbb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=526&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<h2>What is our blood made of?</h2>
<p>Human blood, and that of all creatures with backbones (Antarctic ice fish excepted), is red. The colour comes from a chemical known as haem, which contains iron. It’s the iron that is the crucial ingredient for carrying oxygen. Oxygen is needed for our cells to burn sugars, fats and proteins in a controlled way. This provides us with the energy we need to live.</p>
<p>Outside our bodies, we know that when iron is exposed to oxygen, it rusts. And it doesn’t easily “unrust”. But to work as an oxygen carrier in our bodies, iron needs to “rust” and “unrust” on demand - picking up oxygen where it is in plentiful supply (our lungs), and releasing it where it is required (the cells in our organs).</p>
<p>This on/off oxygen switch is made possible with help from complex larger molecules. The first is haem, a flat ring structure that holds an iron atom at its centre. Haem is held closely by proteins known as globin, and this combination forms haemoglobin, which is itself packaged up in red blood cells to be transported around the body.</p>
<hr>
<p><a href="https://theconversation.com/from-animal-experiments-to-saving-lives-a-history-of-blood-transfusions-80391"><em>Infographic - From animal experiments to saving lives: a history of blood transfusions</em></a></p>
<hr>
<p>The molecular structure of haemoglobin is delicately tuned to allow it to bind oxygen in the lungs and drop it off in areas where there is less oxygen available.</p>
<p>Red cells are specialised parcels, lacking DNA, that are able to squeeze through the tiniest capillaries, down to four millionths of a meter (equivalent to roughly half their diameter). Their donut shape maximises their surface area to make sure they can efficiently deliver oxygen, while keeping them small enough to fit through the smallest blood vessels.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=286&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=286&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=286&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=360&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=360&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176861/original/file-20170705-4592-1q4j491.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=360&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Antarctic ice fish managed to evolve past needing red blood cells and instead absorbs oxygen.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>More than just the red stuff</h2>
<p>As well as red cells, our blood contains other cells and chemicals that repair and maintain the transport system and send signals around the body.</p>
<p>White blood cells, also known as leukocytes, repel or destroy invaders. Some white blood cells (lymphocytes) manufacture molecules known as antibodies that tag viruses and bacteria for destruction, while others called neutrophils and macrophages (literally “big eaters”) engulf bacteria, fungi and parasites to keep our circulation clean. When neutrophils have done their job you sometimes might see them as the main component of pus.</p>
<p>Platelets are very small fragments of larger cells called megakaryocytes. They react to any breaches to the walls of blood vessels, gathering together and triggering reactions that form a plug (or a clot) for the damaged section. If a person doesn’t have enough platelets, they can suffer from uncontrollable bleeding.</p>
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<h2>Where does it come from?</h2>
<p>All blood cells (red cells, white cells and platelets) develop from haematopoietic (literally meaning “blood-making”) stem cells, located in the bone marrow. It has recently been found that many <a href="https://www.ncbi.nlm.nih.gov/pubmed/28329764">platelets are made in the lungs</a>, from megakaryocytes that have migrated there from the bone marrow.</p>
<p>As stem cells develop, they progressively specialise into the many different types of blood cells, making developmental choices along the way. The specialisation of cells during development is tightly controlled by a symphony of growth factors. In some types of blood cancers and serious diseases, stem cell or bone marrow transplants can be used to “reboot” the blood making system.</p>
<p>As our knowledge of the control of blood cell development grows, we’re making progress towards being able to <a href="https://www.newscientist.com/article/2131517-human-blood-stem-cells-grown-in-the-lab-for-the-first-time/">reproduce this process in cells grown in the laboratory</a>. This is still some time away from being a broadly available process, but an exciting area to watch as it develops.</p>
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<p><em>Update: the sentence outlining the shape of red blood cells was incorrect and has been reworded.</em></p><img src="https://counter.theconversation.com/content/75064/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Irving is employed by the Australian Red Cross Blood Service and has research collaborations with others receiving NHMRC and ARC research grants.
Australian governments fund the Australian Red Cross Blood Service for the provision of blood, blood products and services to the Australian community.</span></em></p>Everything you never knew about the red stuff in your veins.David Irving, Adjunct Professor, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.