The most important of several blood group systems for typing human blood, based on the presence or absence of two antigens (A and B) on the surface of red blood cells. Blood types are A, B, AB, and O.
Each individual has a particular blood type that is identified by one of the major blood groups - A, B, O, or AB. Matching of donor and recipient by blood group is essential to organ transplantation. Jump to Top
the major blood groups system. People can be either A, B, O or AB. Among the donor population, the approximate breakdown of blood groups is: Group O - 45%; Group A - 40%; Group B - 11% and Group AB - 4%.