Hypersensitivity reactions in the small intestine. VII. Induction of the intestinal phase of murine graft-versus-host-reaction by Lyt 2- T cells activated by I-A alloantigens.

This study has examined the nature of the T lymphocytes and the alloantigens that induce the intestinal phase of graft-versus-host reaction in unirradiated F1 mice. Parental spleen cells were depleted of T cells subsets by treatment with anti-Lyt monoclonal antibodies and complement, and we show that Lyt 2- cells alone induce the increased lymphocytic infiltration of the epithelium that characterizes the intestinal graft-versus-host reaction. Lyt 2- cells are also required to induce some of the associated crypt hyperplasia, but the full crypt changes require both Lyt 2- and Lyt 2+ T cells. In intra-H-2 recombinant congenic F1 mice with graft-versus-host reaction, a disparity at the I-A locus was alone sufficient and necessary for crypt hyperplasia and increased intraepithelial lymphocyte counts, while an I-J incompatibility led to suppression of both these indices. The results support the hypothesis that the intestinal pathology of acute GVHD is induced by class II MHC-restricted delayed-type hypersensitivity effector T cells.