IFNγR^−/− Tconvs do not cause life-threatening GVHD. (A) Effect of IFNγR on GVHD and survival (a pool of 4 independent experiments). Allo-HSCT (B6 [H-2^b] → Balb/c]H-2^d, CD45.2⁺]) was performed as follows. T cell–depleted bone marrow cells (TCD BMs; 5 × 10⁶; CD45.1⁺ B6) and 5 × 10⁵ Tconvs (CD45.2⁺ B6, either WT or IFNγR^−/−) were injected into lethally irradiated (925cGy) Balb/c recipient mice. XRT: irradiation control, BM: TCD BM only, WT: TCD BM + WT Tconv, IFNγR^−/−: TCD BM + IFNγR^−/−Tconv, IFNγ^−/−: TCD BM + IFNγ^−/− Tconv. (B-D) One hundred percent donor chimerism is achieved in the IFNγR group. Peripheral blood was analyzed at day 30 after allo-HSCT. The IFNγR group shows higher CD3⁺ T cells and B220⁺ B cells in peripheral blood at day 30 after HSCT (a pool of 3 independent experiments) and better weight maintenance compared with the WT group (n = 4; one representative of 4 independent experiments). (E) Tissue sections of skin, liver, and intestine were graded by a veterinary pathologist in blinded fashion on day 20 after allo-HSCT for acute GVHD according to the Lerner grading system (see “Methods” for details).²¹