ABO blood group system A-type blood, with A2 making up almost all of the rest. These two subgroups are not always interchangeable as far as transfusion is concerned, as some A2 individuals produce antibodies against the A1 antigen. Complications can sometimes arise in rare cases when typing the blood. With the development of DNA sequencing, it has been possible to identify a much larger number of alleles at the ABO locus, each of which can be categorized as A, B, or O in terms of the reaction to transfusion, but which can be distinguished by variations in the DNA sequence. There are six common
Blood type In 1927, Landsteiner, with Philip Levine, discovered the MN blood group system, and the P system. Development of the Coombs test in 1945, the advent of transfusion medicine, and the understanding of ABO hemolytic disease of the newborn led to discovery of more blood groups. , the International Society of Blood Transfusion (ISBT) recognizes 346 blood group antigens which are assigned to 36 blood groups. A popular belief in Japan is that a person's ABO blood type is predictive of their personality, character, and compatibility with others. This belief is also widespread in South Korea and Taiwan. The theory reached