THE INDUCTION OF SKIN-GRAFT TOLERANCE IN MAJOR HISTOCOMPATIBILITY COMPLEX-MISMATCHED OR PRIMED RECIPIENTS - PRIMED T-CELLS CAN BE TOLERIZED IN THE PERIPHERY WITH ANTI-CD4 AND ANTI-CD8 ANTIBODIES

Mice given short courses of anti-CD4 and anti-CD8 monoclonal antibodies became tolerant of allogeneic skin grafted at the same time. Tolerance could be obtained without Tcell depletion across multiple minor antigen mismatches, both in naive and primed animals, demonstrating that peripheral T cells could be tolerized, even if they had been previously activated. Where donor and recipient were incompatible across the whole major histocompatibility complex, specific tolerance could be achieved by using a combination of depleting followed by non-depleting antibodies, where each alone was unsuccessful. Although mice clearly tolerated their original skin grafts, we observed in some strain combinations that a second fresh, but genotypically identical graft, was slowly rejected. Such mice also possessed T cells which could proliferate to donor-type stimulator cells in vitro. Whatever the mechanisms, we have demonstrated that operational transplantation tolerance can be achieved with simple, non-toxic antibody therapy. The introduction of comparable tolerance-inducing regimens in clinical organ transplantation could obviate the need for long-term immunosuppression and its unfortunate side effects.