CD4(+) and CD8(+) T cells each can utilize a perforin-dependent pathway to mediate lethal graft-versus-host disease in major histocompatibility complex disparate recipients

Perforin-deficient (-/-) mice were used as T-cell donors for infusion into irradiated major histocompatibility complex (MHC)-disparate recipients to investigate the requirement for perforin-mediated cytolysis during graft-versus-host disease (GVHD) generation, Administration of 5 x 10(6) C57BL/6 (H2(b)) perforin -/- splenocytes was significantly less effective in inducing GVHD lethality when given to MHC class I + II disparate B10.BR (H2(k)) recipients, as compared with wildtype (+/+) controls, Perforin expression by donor T cells was not required for GVHD induction because recipients given fivefold higher numbers of perforin -/- donor splenocytes uniformly succumbed to lethal GVHD, Because both CD4(+) and CD8(+) donor T cells are required for optimal GVHD lethality in this strain combination, to discern the relative contribution of perforin-mediated cytolysis by CD4(+) and CD8(+) T cells, additional studies were performed, For these latter studies, we used a sensitive assay involving the infusion of highly purified CD4(+) or CD8(+) T cells into sublethally irradiated MHC class II or I disparate recipients, respectively, As compared with recipients of perforin +/+ T cells, recipients of either CD4(+) or CD8(+) perforin -/- T-cell subsets had a significant reduction in GVHD-mediated lethality at T-cell doses that were uniformly lethal, T-cell dose titration studies established that GVHD lethality in recipients of perforin -/- CD4(+) or CD8(+) T cells was reduced by approximately threefold, These data are the first to indicate that approaches to limit perforin-mediated cytolysis should be similarly effective in situations in which CD4(+) or CD8(+) T cells dominate the GVRD response.