Morphology of rat cardiac allografts with permanent survival induced by antithymocyte globulin

In a rat heart transplantation model, permanent graft survival was achieved by anti-thymocyte globulin (ATG) treatment of Wistar Kyoto (WKy) recipients before grafting with PVG/c hearts. Nine hearts with palpable and electrocardiographic (ECG) function 8-20 months after transplantation were studied with histological and immunohistochemical methods. The dominating findings were fibrosis, intimal thickening, thrombosis of vessels, cellular infiltrates, and a high number of cells expressing class II antigens. These findings suggest that reactions compatible with a chronic rejection can be found in long-term surviving rat heart allografts. This rat model may thus be used in further studies of a chronic rejection process.