The role of IAPs in host hematopoietic-derived APCs is dispensable for GVHD. (A-B) In vitro MLR. Isolated splenic CD90.2⁺ T cells from either syngeneic B6 or allogeneic BALB/c animals were cultured with BMDCs derived from B6-WT, B6-cIAP1^−/−, or B6-XIAP^−/− animals for 96 hours (A) or with AT406-pretreated (1 µM; 6 hours) BMDCs derived from B6-WT for 96 hours (B) and analyzed for proliferation after ³H-thymidine incorporation during the last 16 hours of incubation. Representative data of 3 independent experiments are shown. The bar shows the mean ± SEM. (C-E) Both nontreated and AT406-pretreated (1 µM) BMDCs were harvested and stimulated through TLR4 with lipopolysaccharide (LPS; 500 ng/ml) for 16 hours. (C) Bar graphs depicting the percentages of CD80, CD86, I-A^b (MHC class II), and B7H1 (PD-L1) expression on CD11c⁺ DCs are shown. The supernatants were analyzed for IL-6 (D) and TNF-α (E) by ELISA. The data are representative of 3 independent experiments and show the means ± SEMs. (F-G) To make BM chimeras, B6Ly5.2 animals were lethally irradiated with 11 Gy and infused with 5 × 10⁶ BM cells and 5 × 10⁶ splenocytes from syngeneic B6-WT, B6-cIAP1^−/−, or B6-XIAP^−/− donors. Three to 4 months later, B6→B6Ly5.2, cIAP1^−/−→B6Ly5.2, and XIAP^−/−→B6Ly5.2 animals were irradiated with 9 Gy and received 3 × 10⁶ CD90⁺ T cells along with 5 × 10⁶ TCD-BM cells from either syngeneic B6 or allogeneic MHC-mismatched BALB/c donors. Survival (F) and clinical GVHD score (G) (n = 4-10 per group). Pooled data from 2 independent experiments are shown.