Development of tolerance to class II-mismatched renal transplants after a short course of cyclosporine therapy in miniature swine.

Our laboratory has reported previously spontaneous acceptance of class II-matched, single haplotype (but not 2 haplotype), class I-mismatched renal allografts in miniature swine. All class II-mismatched animals rejected acutely regardless of class I matching. We have also demonstrated recently that a short course of high dose (10 mg/kg/day for 12 days) CsA uniformly induces donor-specific tolerance to 2-haplotype, class I-mismatched renal allografts. The survival of 2-haplotype, fully MHC mismatched renal allografts was prolonged by the same treatment, but tolerance was not induced, as all animals rejected eventually. We have now tested this short course of immunosuppressive therapy for its effect on renal allografts mismatched selectively for 2 haplotypes at class II. We have observed long-term graft survival in 5 of 7 animals under these conditions. Each of the 5 acceptor animals was demonstrated to be specifically tolerant by its response either to donor-matched skin grafts or to a second donor-matched kidney transplant without further immunosuppression. These data suggest the existence of a common pathway for induction of specific transplantation tolerance to MHC antigens when these antigens are recognized on vascular endothelium under conditions of altered cytokine production. They also suggest that tolerance induction under these conditions requires matching for either class I or class II antigens, which may have implications for the mechanism by which peripheral tolerance is induced, as well as practical implications for the extension of these results to potential clinical practice.