GPR109A^−/− T cell recipients have reduced pathology and inflammation. Lethally irradiated BALB/c recipients received B6 WT TCD BM and 0.5 × 10⁶ WT or KO T cells. (A) Representative H&E images of GVHD target organs small intestine (SI), large intestine, liver and skin on day 14 after transplant. Arrows indicate high density of infiltrating lymphocytes. (B) Organs were scored for histopathalogic damage at day 14. (C-D) Serum cytokines were measured at 7 days post allo-HCT (C) and 14 days post allo-HCT (D). (E-G) mRNA was extracted from colonic tissue at day 7 post allo-HCT to measure expression of specific intestinal genes. (H-I) Bacterial DNA was extracted from day 7 stool and 16S gene amplicon sequencing to measure alpha diversity (H) and linear discriminate analysis of effect size (LEfSe) analysis comparing bacterial differences between WT and KO T cell recipients (I). Controls are stool collected from WT BALB/c mice. (J) SCFAs from day 7 cecal contents was measured by GC-MS. All comparisons in (B) to (J) were performed by two-tailed unpaired Mann-Whitney Test. Values are means ± standard deviation. *P < .05, **P < .01, ***P < .0001, n = 5-10 mice per group. All results from two independent experiments.