what is abo

The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. It is the most important of the 44 different blood type classification systems currently recognized by the International Society of Blood Transfusions. A persons ABO blood type was used by lawyers in paternity suits, by police in forensic science, and by anthropologists in the study of different populations. The ABO gene indirectly encodes the ABO blood group antigens, and the ABO locus has three main allelic forms: A, B, and O. The A, B, and O blood groups were first identified by Austrian immunologist Karl Landsteiner in 1901. Blood transfusions and organ transplants depend on donors and recipients having compatible blood types, and a mismatch in this, or any other serotype, can cause a potentially fatal adverse reaction after a transfusion, or an unwanted immune response to an organ transplant. The ABO blood group antigens remain of prime importance in transfusion medicine, as they are the most immunogenic of all the blood group antigens.