GVHD- and GVT-associated alloresponses of CD8+ T cells may be dissociated by an IFN-γ-dependent mechanism, whereby CD8+ T cells from IFN-γ receptor-deficient donor mice induced more severe GVHD in allogeneic recipients compared with transfer cells from wild-type donors. The gene discussed is IFNG; the disease is graft versus host disease.