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15 Cards in this Set

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  • Back
All human RBC contain alloantigens. What are these?
They are antigens that vary among individual members of a species of the ABO group.
Regarding the ABO group, what do the A and B genes encode?
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.
What is the result, when people inherit both genes?
The genes are codominant, so people who inherit both are type AB.
What are the genetic requirements for obtaining a certain blood group?
People who are either homozygous AA or heterozygous AO are type A, and people who are BB or BO will be type B.
What exactly are the A and B antigens?
They are carbohydrates that differ by a single sugar. They do not cross react.
What type of sugars do RBC possess/
They have three terminal sugars in common on their surface; N-acetylglucosamine/galactose/ffucose. These 3 sugars form the H antigen.
How does this configure with people who have blood group O.
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.
What are the 4 combinations of the A-B antigen group?
Where are reactive antibodies to the bloodgroups found?
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.
What is the result of the RBC- antibody complex?
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.
Do A and B antigens appear on other tissues?
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.
Can ABO blood group differences affect the neonate?
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.
What is the Rh(D) antigen?
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.
When are these reactions likely to occur?
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.
What test is used for this disorder? What treatment is called for?
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.