Background: The contribution of ABO blood group mismatching on the rate of cardiac homograft failure is uncertain. It has been shown that there is lack of expression of A and B blood group antigens on fresh and cryopreserved homograft valves. However, expression of these antigens on the homograft vessel conduit has not been reported.
Methods: Unused portions of cryopreserved pulmonary artery homografts (n = 16) were immunohistochemically stained and examined for expression of endothelial cell marker CD31 and A and B blood group antigens. The staining pattern for each antigen was described. Comparison of homograft donor blood group (as determined by immunostaining) to the blood group reported by the homograft supplier was made.
Results: Staining of CD31 and A and B blood group antigens was poor on the luminal surface (tunica intima) of the homograft conduit but strong in the vaso vasorum of the tunica media and adventitia. Homograft donor blood group was consistent with the reported donor blood group in 15 of 16 specimens (4 group A, 3 group B, 8 group O). In one specimen (reported as group O), we detected strong expression of CD31 and A antigen on the endothelium of the vaso vasorum.
Conclusions: Cryopreserved homografts strongly express A and B blood group antigens on well-preserved endothelial surfaces of the medial and adventitial vaso vasorum. The significance of this finding with regard to the immunologic response to mismatched ABO blood group antigens and homograft longevity is uncertain.