APG101 prevents GVHD in a MHC class I and II–mismatched parent → F1 BMT model. (A-E) Lethally irradiated B6D2F1 recipient mice were reconstituted with BM from B6 mice without or with B6-derived spleen cells (SCs) and were treated with PBS or APG101 starting 1 day before transplantation (day −1) or with APG101 starting 6 (day 6) or 13 days (day 13) after transplantation. Weight reduction (A), GVHD-scores (B), and survival (C) were determined. (C): BM+SC (PBS, day −1) versus BM+SC (APG101, day −1), *P < .05; versus BM+SC (APG101, day 6), **P < .01; versus BM+SC (APG101, day 13), P = .12^ns. Surviving animals/total animals treated are indicated in (C). On day 16 after transplantation paraffin sections of ileum, colon, and liver of 7 to 10 animals/treatment group were analyzed for histologic signs of GVHD, that is, inflammation, active caspase-3 (*P < .05, ***P < .001). (D) On day 16 after transplantation active caspase-3 was stained at room temperature on colon sections of BM + spleen cells transplanted mice treated with PBS or APG101 on day −1 (Zeiss Axiphot microscope, Plan-Neofluar objective lens, 20× magnification, 0.50 numeric aperture, JVC-KY-F75U digital camera and DISKUS Version 4.5 software). (E) Data represent the combination of 2 individual experiments.