Immunologic mechanisms of cardiac transplant rejection

The successful application of cardiac transplantation as a useful therapeutic procedure has been the result of improved surgical techniques and the effective immunosuppression of cardiac rejection. Despite the improvements that have led to the successful application of cardiac transplantation, there are important limitations in our understanding and ability to manipulate the immune-mediated rejection of the donor heart by the host. Methods that allow for improved preservation of the donor heart are necessary to provide the opportunity to match more carefully the donor and recipient for histocompatibility antigens that stimulate rejection of the graft. Clinical data in humans and experimental studies in animals demonstrate that the rejection of the heart is stimulated by a wide variety of histocompatibility antigens, many of which may be neutralized by donor-recipient matching. The immunologic mechanisms that influence the survival of the graft include (1) hyperacute rejection of the graft by recipient antibody directed against foreign antigens of the donor heart, (2) T lymphocyte-mediated acute cellular rejection of the graft, and (3) chronic rejection of the graft associated with the emergence of cardiac graft arteriosclerosis in otherwise successful long-term graft recipients. An increased understanding of these processes will provide opportunities to improve cardiac transplant outcome.