CARDIAC ALLOTRANSPLANTATION ACROSS THE ABO-BLOOD GROUP BARRIER BY THENEUTRALIZATION OF PREFORMED ANTIBODIES - THE BABOON AS A MODEL FOR THE HUMAN

The baboon, like the human, expresses A and/or B blood group antigens on its tissues. Anti-A and anti-B antibodies are directed against thes e antigens, the epitopes of which are carbohydrate structures. Portion s of these carbohydrates have been synthesized (trisaccharides A and B , respectively). When infused intravenously, the synthetic trisacchari des form a complex with the specific antibodies and neutralize their a ctivity preventing them from binding to the antigen targets on a trans planted organ. In nonimmunosuppressed, hyperimmunized baboons, the con tinuous intravenous infusion of the specific trisaccharide alone (for 6 days) inhibited rejection of ABO-incompatible cardiac allografts, ex tending survival from a mean of 19 min (n = 3) to 8 days (n = 2), at w hich time the grafts failed from cellular (not vascular) rejection. Th e combination of long-term pharmaco logic immunosuppression plus trisa ccharide infusion (for periods of 8 to 19 days) extended survival to a mean of >28 days (n = 4) with one heart functioning >52 days. Accommo dation clearly occurred in three of the four cases. This form of thera py may permit cadaveric organ allotransplantation across the ABO blood -group barrier in the human.