Homograft Crossmatching Is Unnecessary due to the Absence of Blood Group Antigens

Background. Homograft valves are subject to calcification and structural degeneration in the long term. Blood group matching is performed in many centers, and it remains controversial whether immunologic responses associated with potential blood group incompatibility contribute to the degeneration of unmatched homografts. We studied the expression of carbohydrate blood group antigens on valve endothelium of thawed aortic homograft valves and freshly harvested human cardiac valves. Methods. Cryopreserved human aortic homograft valves and freshly harvested human aortic, pulmonary, mitral, and tricuspid valves were incubated with antibodies to A, B, and O blood group antigens. Results. Cardiac microvascular endothelium stained positively with antiendothelial CD31 antibody in both cryopreserved and fresh tissue. Cryopreserved valve endothelial lining rarely stained positively for CD31, in contrast to fresh valves, which always stained positive. Cryopreserved or fresh cardiac microvascular endothelium strongly expressed A, B, or H antigens. In contrast, ABH antigens were not detectable on homograft or fresh cardiac valve endothelium. Conclusions. The absence of expression of carbohydrate antigen on valvular endothelium suggests that blood group incompatibility does not play a significant role in homograft degeneration.