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.