IDO-based GVHD suppression is GCN2 independent. Wt (filled symbols) or IDO^−/− (open symbols) BALB/c mice were lethally irradiated and infused with B6 BM with or without (circles) 2 × 10⁶ wt (squares) or GCN2^−/− (triangles) T cells. Survival is shown. For wt versus IDO^−/− given wt cells, P < .001; for wt versus IDO^−/− given GCN2^−/− T cells, P = .001; for wt versus GCN2^−/− in wt recipients, P = .38; for wt versus GCN2^−/− in IDO^−/− recipients, P = .53. Data are representative of 4 independent experiments with n = 7-8 mice/group.