Monoclonal antibodies to CD4, CD8 and CD11a can be used in vivo either to deplete or functionally block T cells to create a tolerance permissive environment. Short courses of non-depleting CD4 and CD8 antibodies were used to induce tolerance separately in CD4+ and CD8+ T cells either to foreign immunoglobulins, bone marrow, or skin grafts. Tolerance was obtained to minor (non-MHC) transplantation antigens without T cell depletion even in actively sensitized mice, or to MHC plus minor antigens...