We have recently shown that donor CD4-enriched cells of Th2 cytokine phenotype, generated by treating mice in vivo with a combination of interleukin-2 (IL-2) and IL-4, prevent lipopolysaccharide-induced, tumor necrosis factor-alpha-mediated lethality during graft-versus-host reaction. To assess the potential regulatory role of such Th2-type cells in lethal graft-versus-host disease (GVHD) and graft rejection, we used a fully allogeneic murine transplant model using sublethally irradiated hosts (B6-->C3H, 500 cGy). Such recipients generated a strong host-versus-graft response, as reflected by their ability to reject T-cell-depleted inocula. The administration of T-cell-containing donor whole spleen inocula resulted in alloengraftment, but such recipients developed lethal GVHD. However, mice receiving sequential donor whole spleen (day 0) and CD4-enriched, Th2-type (day 1) populations engrafted, and had prolonged survival with protection from histologically defined tissue injury associated with GVHD. The findings in this fully allogeneic model thus extend our previous observations and indicate that the transfer of donor Th2-type cells may be an important strategy for regulating GVHD. Furthermore, the sequential “Th1(-)-->Th2-type” donor cell transfer described in this report represents a novel approach for abrogating graft rejection with concomitant control of GVHD and illustrates the importance of kinetics in the interaction of functionally distinct donor T-cell populations.