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15 Cards in this Set
- Front
- Back
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All human RBC contain alloantigens. What are these?
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They are antigens that vary among individual members of a species of the ABO group.
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Regarding the ABO group, what do the A and B genes encode?
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They encode enzymes that add specific sugars to the end of a polysaccharide chain on the surface of many cells. people who inherit neither gene, are type O.
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What is the result, when people inherit both genes?
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The genes are codominant, so people who inherit both are type AB.
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What are the genetic requirements for obtaining a certain blood group?
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People who are either homozygous AA or heterozygous AO are type A, and people who are BB or BO will be type B.
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What exactly are the A and B antigens?
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They are carbohydrates that differ by a single sugar. They do not cross react.
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What type of sugars do RBC possess/
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They have three terminal sugars in common on their surface; N-acetylglucosamine/galactose/ffucose. These 3 sugars form the H antigen.
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How does this configure with people who have blood group O.
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These individuals have only the H antigen on the surface. people who are of group A have N-acetylgalactosamine added to the H antigen whereas those of group B have galactose added to the H antigen.
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What are the 4 combinations of the A-B antigen group?
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A/B/AB/O.
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Where are reactive antibodies to the bloodgroups found?
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The plasma has antibody against the absent antigens, that is people with blood group A have antibodies to B in their plasma. These antibodies are formed against cross reacting bacterial or food antigens are first detectable at 3-6 months of age and are of the IgM class.
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What is the result of the RBC- antibody complex?
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This complex activates complement and a reaction consisting of shock caused by large amounts of C3a and C5a (anaphylatoxins) and hemolysis caused by C5, C6, C7, C8, and C9 (membrane attack complex) occurs.
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Do A and B antigens appear on other tissues?
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The A and B antigens appear on the cells of many tissues. These antigens can be secreted in saliva and other body fluids. Secretion is controlled by a secretor gene. App 85% of people carry the dominant form of the gene, which allows secretion to occur.
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Can ABO blood group differences affect the neonate?
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ABO blood group differences can lead to neonatal jaundice and anemia. Mothers with blood group O have antibodies against both A and B antigens. These IgG antibodies can pass the placenta, and if the fetus is blood group A or B, cause lysis of fetal red cells. Mothers with either blood group A or B, have a lower risk of having a neonate with jaundice b/c these mothers produce antibodies to either B or A antigens, respectively,that are primarily IgM, and IgM does not pass the placenta.
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What is the Rh(D) antigen?
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About 85% of humans have RBC that express the Rh(D) antigen, i.e. are Rh(D)+. When an Rh(D)- person is transfused with Rh(D)+ blood or when an Rh(D)- woman has an Rh(D)+ fetus(the D gene being inherited from the father), the Rh(D) antigen, will stimulate the development of antibodies.
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When are these reactions likely to occur?
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This occurs most often when the Rh(D)+ RBC of the fetus leak into the maternal circulation during delivery of the first Rh(D)+ child. Subsequent, Rh(D)+ pregnancies are likely to be affected by the mothers anti-D antibody and hemolytic disease of the newborn often results. This disease results from the passage of maternal IgG anti-Rh(D) antibodies through the placenta to the fetus, with subsequent lysis of the fetal RBC.
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What test is used for this disorder? What treatment is called for?
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The direct antiglobulin(Coombs) test is typically positive. The problem is prevented by administration of high titerRh(D) immune globulins(Rho-Gam) to an Rh(D)- mother at 28 weeks of gestation and immediately upon the delivery of an Rh(D)+ child. These antibodies attach to Rh(D)+ RBC and prevent their acting as sensitizing antigen.
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