Laboratory work for the coming year will be devoted to studies of immunologic manipulation in cardiac transplantation and characterization of physiologic events during cardiac allograft rejection. Although markedly depressed immunocompetence is present in patients following total lymph node irradiation for treatment of malignancies, a similar regimen of nodal irradiation in dogs followed within several days by cardiac allografting results in an accelerated form of rejection rather than the anticipated prolongation of graft survival. Studies are planned to elucidate the mechanisms of this form of accelerated rejection and to determine the time interval after nodal irradiation during which this phenomenon occurs. The efficacy of combining standard immunosuppressive drugs with total nodal irradiation will then be evaluated. Study will continue on the mechanism of chicken antirat lymphocyte globulin (CARLG). Our current hypothesis is that this agent at least in part by binding to donor histocompatibility antigens with the antigen antibody complex functioning as an immunoregulatory signal. BIBLIOGRAPHIC REFERENCES: Morris, R.E., Hanley, J.M., Griepp, R.B., and Shumay, N.E.: Chicken antilymphocyte globulin: a source of heterologous enhancing antibody. Transplant. Proc. 9:1037, 1977. Bieber, C.P., Griepp, R.B., Oyer, P.E., David, L.A. and Stinson, E.B.: Relationship of rabbit ATG serum clearance rate to circulating T-cell level, rejection onset, and survival in cardiac transplantation. Transplant. Proc. 9:1031, 1977.