Allograft tolerance induction in adult mice associated with functional deletion of specific CTL precursors.

Rejection of H-2 class I bm 1 mutant skin allografts by B6 recipient mice is mediated by a population of CD8+ anti-bm1 cytotoxic T-lymphocytes that produces and consumes its own T helper factor in response to bm1 skin allografts (dual function CTL). Previously we have demonstrated that transfusion of allogeneic lymphocytes across an H-2 class I disparity induces specific long-lasting skin allograft survival. We now show that intravenous injection of allogeneic spleen cells across the bm1 mutant disparity results in a temporary decrease of donor-reactive CTLp in the spleen of recipient mice, lasting for approximately five weeks. The sponge matrix allograft model was used to show that allograft tolerance is caused by a specific functional clonal deletion of CTLp within the allograft. We propose that dual function CTL are vetoed by donor T cells, resulting in skin allograft tolerance.