{"id":4650,"date":"2019-06-24T14:02:37","date_gmt":"2019-06-24T14:02:37","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/8-6-variation-in-blood-types-3\/"},"modified":"2023-11-30T18:46:54","modified_gmt":"2023-11-30T18:46:54","slug":"8-6-variation-in-blood-types-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/8-6-variation-in-blood-types-3\/","title":{"raw":"6.5\u00a0Variation in Blood Types","rendered":"6.5\u00a0Variation in Blood Types"},"content":{"raw":" \r\n\r\n[caption id=\"attachment_2701\" align=\"aligncenter\" width=\"602\"]\"Blood Figure 6.5.1 A phlebotomist draws blood from a blood donor.<\/em>[\/caption]\r\n

Giving the Gift of Life<\/h1>\r\nDid you ever donate blood? If you did, then you probably know that your blood type is an important factor in blood transfusions. People vary in the type of blood they inherit, and this determines which type(s) of blood they can safely receive in a transfusion. Do you know your blood type?\r\n
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What Are Blood Types?<\/h1>\r\n<\/div>\r\n

[pb_glossary id=\"2702\"]Blood[\/pb_glossary] is composed of cells suspended in a liquid called plasma. There are three types of cells in blood: red blood cells, which carry oxygen; white blood cells, which fight infections and other threats; and platelets, which are cell fragments that help blood clot.\u00a0[pb_glossary id=\"2703\"]Blood type[\/pb_glossary]<\/strong>\u00a0(or blood group) is a genetic characteristic associated with the presence or absence of certain molecules, called antigens, on the surface of red blood cells. These molecules may help maintain the integrity of the cell membrane, act as receptors, or have other biological functions. A\u00a0blood group system<\/strong>\u00a0refers to all of the [pb_glossary id=\"5521\"]gene[\/pb_glossary](s), [pb_glossary id=\"5449\"]alleles[\/pb_glossary], and possible [pb_glossary id=\"6039\"]genotypes[\/pb_glossary]\u00a0and [pb_glossary id=\"2477\"]phenotypes[\/pb_glossary]\u00a0that exist for a particular set of blood type antigens. Human blood group systems include the well-known ABO and Rhesus (Rh) systems, as well as at least 33 others that are less well known.<\/p>\r\n\r\n

Antigens and Antibodies<\/h2>\r\n[pb_glossary id=\"2704\"]Antigens[\/pb_glossary]<\/strong>\u00a0\u2014\u00a0<\/strong>such as those on the red blood cells \u2014 are molecules that the immune system identifies as either self (produced by your own body) or non-self (not produced by your own body). Blood group antigens may be [pb_glossary id=\"1593\"]proteins[\/pb_glossary], [pb_glossary id=\"5655\"]carbohydrates[\/pb_glossary], glycoproteins (proteins attached to chains of sugars), or glycolipids (lipids attached to chains of sugars), depending on the particular blood group system. If antigens are identified as non-self, the immune system responds by forming antibodies that are specific to the non-self antigens. [pb_glossary id=\"5659\"]Antibodies[\/pb_glossary]<\/strong> are large, Y-shaped proteins produced by the immune system that recognize and bind to non-self antigens. The analogy of a lock and key is often used to represent how an antibody and antigen fit together, as shown in the illustration below (Figure 6.5.2). When antibodies bind to antigens, it marks them for destruction by other immune system cells. Non-self antigens may enter your body on pathogens (such as bacteria or viruses), on foods, or on red blood cells in a blood transfusion from someone with a different blood type than your own. The last way is virtually impossible nowadays because of effective blood typing and screening protocols.\r\n\r\n[caption id=\"attachment_2705\" align=\"aligncenter\" width=\"492\"]\"Antibody Figure 6.5.2 Model of antigen and matching antibody. Antibodies will detect antigens based on a match in 3-dimensional shape, as per the lock and key model.<\/em>[\/caption]\r\n

Genetics of Blood Type<\/h2>\r\nAn individual\u2019s [pb_glossary id=\"2703\"]blood type[\/pb_glossary] depends on which [pb_glossary id=\"5449\"]alleles[\/pb_glossary] for a blood group system were inherited from their parents. Generally, blood type is controlled by alleles for a single [pb_glossary id=\"5521\"]gene[\/pb_glossary], or for two or more very closely linked genes. Closely linked genes are almost always inherited together, because there is little or no recombination between them. Like other genetic traits, a person\u2019s blood type is generally fixed for life, but there are rare instances in which blood type can change. This could happen, for example, if an individual receives a bone marrow transplant to treat a disease, such as leukemia. If the bone marrow comes from a donor who has a different blood type, the patient\u2019s blood type may eventually convert to the donor\u2019s blood type, because red blood cells are produced in bone marrow.\r\n
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ABO Blood Group System<\/h1>\r\n<\/div>\r\nThe\u00a0ABO blood group system<\/strong> is the best known human blood group system. [pb_glossary id=\"2704\"]Antigens[\/pb_glossary] in this system are glycoproteins. These antigens are shown in the list below. There are four common blood types for the ABO system:\r\n
    \r\n \t
  1. Type A, in which only the A antigen is present.<\/li>\r\n \t
  2. Type B, in which only the B antigen is present.<\/li>\r\n \t
  3. Type AB, in which both the A and B antigens are present.<\/li>\r\n \t
  4. Type O, in which neither the A nor the B antigen is present.<\/li>\r\n<\/ol>\r\n

    Genetics of the ABO System<\/h2>\r\nThe ABO blood group system is controlled by a single[pb_glossary id=\"5521\"] gene[\/pb_glossary] on chromosome 9<\/a>. There are three common [pb_glossary id=\"5449\"]alleles[\/pb_glossary] for the gene, often represented by the letters A , B , and O. With three alleles, there are six possible genotypes for ABO blood group. Alleles A and B, however, are both dominant to allele O and codominant to each other. This results in just four possible phenotypes (blood types) for the ABO system. These genotypes and phenotypes are shown in Table 6.5.1.\r\n\r\nTable 6.5.1<\/strong>\r\n\r\nABO Blood Group System: Genotypes and Phenotypes<\/em>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    ABO Blood Group System<\/strong><\/td>\r\n<\/tr>\r\n
    Genotype<\/strong><\/td>\r\nPhenotype (Blood Type, or Group)<\/strong><\/td>\r\n<\/tr>\r\n
    AA<\/td>\r\nA<\/td>\r\n<\/tr>\r\n
    AO<\/td>\r\nA<\/td>\r\n<\/tr>\r\n
    BB<\/td>\r\nB<\/td>\r\n<\/tr>\r\n
    BO<\/td>\r\nB<\/td>\r\n<\/tr>\r\n
    OO<\/td>\r\nO<\/td>\r\n<\/tr>\r\n
    AB<\/td>\r\nAB<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe diagram below (Figure 6.5.3) shows an example of how ABO blood type is inherited. In this particular example, the father has blood type A (genotype AO) and the mother has blood type B (genotype BO). This mating type can produce children with each of the four possible ABO [pb_glossary id=\"2477\"]phenotypes[\/pb_glossary], although in any given family, not all phenotypes may be present in the children.\r\n\r\n[caption id=\"attachment_2706\" align=\"aligncenter\" width=\"590\"]\"Example Figure 6.5.3 Example of ABO blood group inheritance.<\/em>[\/caption]\r\n\r\n
    \r\n\r\nMedical Significance of ABO Blood Type<\/span>\r\n\r\n<\/div>\r\nThe ABO system is the most important blood group system in blood transfusions. If red blood cells containing a particular ABO antigen are transfused into a person who lacks that antigen, the person\u2019s immune system will recognize the antigen on the red blood cells as non-self. Antibodies specific to that antigen will attack the red blood cells, causing them to agglutinate (or clump) and break apart. If a unit of incompatible blood were to be accidentally transfused into a patient, a severe reaction (called acute hemolytic transfusion reaction<\/a>) is likely to occur, in which many red blood cells are destroyed. This may result in kidney failure, shock, and even death. Fortunately, such medical accidents virtually never occur today.\r\n\r\nThese antibodies are often spontaneously produced in the first years of life, after exposure to common microorganisms in the environment that have antigens similar to blood antigens. Specifically, a person with type A blood will produce anti-B antibodies, while a person with type B blood will produce anti-A antibodies. A person with type AB blood does not produce either antibody, while a person with type O blood produces both anti-A and anti-B antibodies. Once the antibodies have been produced, they circulate in the plasma. The relationship between ABO red blood cell antigens and plasma antibodies is shown in Figure 6.5.4.\r\n\r\n \r\n\r\n[caption id=\"attachment_2555\" align=\"aligncenter\" width=\"1016\"]\"Image Figure 6.5.4 The relationship between ABO red blood cell antigens and plasma antibodies.<\/em>[\/caption]\r\n\r\n
    \r\n\r\nThe antibodies that circulate in the plasma are for different antigens than those on red blood cells, which are recognized as self antigens.<\/em>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_2713\" align=\"alignright\" width=\"273\"]\"Blood Figure 6.5.5 You can always donate blood to someone who has the same blood type as yours, but you may or may not be able to donate to people who have other blood types, as indicated in this diagram.<\/em>[\/caption]\r\n\r\nWhich blood types are compatible and which are not? Type O blood contains both anti-A and anti-B antibodies, so people with type O blood can only receive type O blood. However, they can\u00a0donate<\/em>\u00a0blood to people of\u00a0any<\/em>\u00a0ABO blood type, which is why individuals with type O blood are called\u00a0universal donors.<\/strong>\u00a0Type AB blood contains neither anti-A nor anti-B antibodies, so people with type AB blood can receive blood from people of any ABO blood type. That\u2019s why individuals with type AB blood are called\u00a0universal recipients.<\/strong>\u00a0They can donate blood, however,\u00a0only<\/em> to people who also have type AB blood. These and other relationships between blood types of donors and recipients are summarized in the simple diagram to the right.\r\n

    Geographic Distribution of ABO Blood Groups<\/h3>\r\nThe frequencies of blood groups for the ABO system vary around the world. You can see how the A and B alleles and the blood group O are distributed geographically on the maps in Figure 6.5.6.\r\n