[Role of the ABO system in transplants and grafts].

The structures and locations of the glucidic molecules in the ABO system vary according to the tissues, ontogenesis and individuals. Although their physiological role is not well established, they are considered as very important factors in transplantations. When the ABO identity is not taken into account, hyperacute, acute, and chronic rejections, or hemolysis and tolerance phenomenon may occur but the incidence of these problems varies according to the tissues. In ABO minor mismatch, the transplantation is always possible, but is associated with worse long term graft survival, except for bone marrow. In ABO major mismatch, the frequency of hyperacute rejections remains the main problem, although the frequency is nil for bone marrow, very low for the liver, quite important for the kidney, and high for heart transplantations. Thus, the ABO group barrier is not absolute but must still be taken into account for allogenic transplantations.