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AIPMTAIPMT 1991Body Fluids and Circulation
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Human blood groups are special characteristics of blood in human and related primates due to presence of genetically controlled antigens and antibodies. ABO blood groups were the first to be discovered and are the most important in assuring safe blood transfusion. This system reflect the presence or absence of A and B agglutinogens (antigen) which are carried on the surface of plasma membrane of red blood cells. The ABO blood groups are determined by the gene I having three alleles - IA,IB,I0. In human being, there are present two antigens A and B produced by IA and IB alleles respectively. These antigens are always present on the surface of RBCs. Also are present two antibodies in the plasma-anti A and anti B. Blood group AB has both antigens A and B but no antibodies.