Prolonged survival of cardiac allografts in rats following the administration of heat-treated donor lymphocytes. A possible immunosuppressive role for class I major histocompatibility complex antigens.

Pretransplant transfusions of spleen and lymph node cells heated to 45 degrees C or 50 degrees C for 1 hr prolong the survival of subsequent donor-specific heart grafts in the fully allogeneic donor-host combination DA (RT1a)----AS (RT1l). The results are comparable to survival times recorded following pretransplant transfusions of purified donor specific red blood cells (RBC) in the same strain combination. Both class I and class II major histocompatibility complex (MHC) antigens are serologically detectable on heat-treated cells; by contrast only class I antigens are expressed on red blood cells. Although heat-treated cells stimulate alloantibody formation, they fail to provoke a proliferative response in an in vivo host-versus-graft assay. Both red blood cells and heat-treated inocula persist in the host for long periods, possibly an important consideration in relation to their capacity to prolong the survival of subsequent donor strain allografts. The experimental data support the contention that class I MHC antigens can be immunosuppressive in the context of allografting. The present results recall the experiments carried out early in the century, which used heat-treated tumor cells to prolong the survival of subsequent viable tumor allografts, and which are sometimes cited as the first example of active enhancement.