Autopsy Pathology (AP) in primate recipients of heterotopic xenografts (XG) functioning for >60 days

characterized in its mildest form by myocyte vacuolization and interstitial edema and its severest form by coagulative necrosis. No cellular infiltrates were observed and intramyocardial hemorrhage was rare. Vessels and capillaries were variably congested and thrombosed, but were often normal. Concentric intimal thickening resembling classic allograft vasculopathy was also observed (n 3). IHC in nine hearts showed that C5b was consistently negative, whereas there was focal to diffuse, moderately strong IgG and IgM staining of small vessel and capillary endothelium. Hearts with the least rejection tended to have weaker and more focal staining. Conclusions: XG vascular rejection in this model showed changes different from those previously described (less hemorrhage and thrombosis; more edema and coagulative necrosis). The notable preservation of myocardium in a number of recipients emphasizes the potential for successful cardiac xenotransplantation.