Absence of IAPs in host exacerbates GVHD in allo-BMT. B6-WT and B6-XIAP^−/− animals received 10 Gy on day −1 and received transplants of 3 × 10⁶ CD90.2⁺ splenic T cells along with 5 × 10⁶ TCD-BM cells from either syngeneic B6 or allogeneic MHC-mismatched BALB/c donors. (A) Survival (n = 5-13 per group). Pooled data from 3 independent experiments are shown. ***P < .001, when allogeneic WT control and allogeneic XIAP^−/− animals are compared. (B) Donor T-cell (H-2k^d+CD4⁺ or H-2k^d+CD8⁺) expansion in spleen, liver, and intraepithelial cells (IECs) on day 7 after allo-BMT (n = 4-6 per group, pooled from 2 experiments). The bar shows the mean ± SEM. (C-D) Serum levels of IFN-γ (C) and TNF-α (D) on day 7 after allo-BMT (n = 4-6 per group, pooled from 2 experiments). *P < .05. The bar shows the mean ± SEM. (E) The histopathological GVHD score in GI tract (small and large intestines) on day 7 after allo-BMT (n = 4-6 per group, pooled from 2 experiments). **P < .01. The bar shows the mean ± SEM. (F) Survival. B6-WT and B6-cIAP1^−/− animals received 10 Gy on day −1 and received transplants of 3 × 10⁶ CD90.2⁺ splenic T cells along with 5 × 10⁶ TCD-BM cells from either syngeneic B6 or allogeneic MHC-mismatched BALB/c donors (n = 3-16 per group). Pooled data from 3 independent experiments are shown. *P < .05, when allogeneic WT control and allogeneic cIAP1^−/− animals are compared.