Acute graft-versus-host disease (GVHD) is thought to be initiated by alloreactive type 1 T cells that secrete γ-interferon (IFN-γ). IFN-γ induces the production of inflammatory cytokines, e.g., tumor necrosis factor-α and interleukin (IL)-1, which are the distal mediators of GVHD. We demonstrate that the transplantation of polarized type 2 murine T cells (i.e., cells secreting IL-4 but not IFN-γ) together with T-cell-depleted bone marrow results in a significant increase in survival(P<0.001) after bone marrow transplantation across minor histocompatibility barriers (B10.BR→CBA/J). Further analysis demonstrated that increased survival in recipients of polarized type 2 T cells correlated with diminished production of both IFN-γ and tumor necrosis factor-α but with increases in IL-4 2 weeks after transplantation. Despite improved survival, histologic changes of GVHD were evident in oral mucosal and hepatic tissues at 7 weeks after bone marrow transplantation. These data provide further evidence that inflammatory cytokines in the immediate posttransplant period are pivotal to the development of mortality but that they do not correlate with individual target organ damage.