Donor-derived interferon γ is required for inhibition of acute graft- versus-host disease by interleukin 12

Abstract

We have demonstrated that a single injection of interleukin (IL)-12 on the day of bone marrow transplantation (BMT) inhibits acute graft-versus- host disease (GVHD) in mice. This effect of IL-12 can be diminished by anti- interferon (IFN)-γ mAb. To determine the mechanism by which IFN-γ affects IL-12-mediated GVHD protection, we have compared the effect of IL-12 on GVHD in C57BL/6 wild-type (WT) or IFN-γ gene knockout (GKO) recipients of fully major histocompatibility complex plus minor antigen-mismatched allogeneic BMT from WT or GKO BALB/c mice. Lethal acute GVHD was readily induced in the absence of IFN-γ. IL-12 inhibited GVHD mortality to a similar extent in WT and GKO recipients of WT allogeneic BMT. However, neither WT nor GKO recipients were protected by IL-12 from GVHD induced by GKO allogeneic BMT. Moreover, the effective inhibition of host-reactive donor T cell activation and expansion that is associated with IL-12-mediated GVHD protection was dependent on the ability of BALB/c donors to produce IFN-γ. These results demonstrate that (a) acute GVHD can be induced in the absence of IFN-γ, (b) host IFN-γ does not play a critical role in IL-12-induced GVHD protection, and (c) the protective effect of IL-12 against GVHD is dependent on the ability of the donor to produce IFN-γ.