Recipients of GPR109A^−/− T cells have fewer donor T cells post allo-HCT compared to WT. Lethally irradiated BALB/c recipients received B6 WT TCD BM and 0.5 × 10⁶ WT or KO T cells. (A-B) Live, CD45⁺, CD3⁺, H-2kb⁺ donor CD4⁺ and CD8⁺ T cell percentages (top) and numbers (bottom) are shown from spleen, small intestine (SI) lamina propria and colon lamina propria on day 7 and day 14 post allo-HCT. (C-D) Live, CD45⁺, CD3⁺, H-2kb⁺ donor effector memory CD4⁺ and CD8⁺ T cell percentages and numbers were analyzed from indicated tissues. (E) Live, CD45⁺, CD3⁺, H-2kb⁺, CD4⁺ donor regulatory T cell percentages analyzed for the 3 tissues on day 7 and 14 and (F) ratio of Tregs to CD4⁺ T cells analyzed. (G) Percent and number of T-bet⁺ Th1 cells on day 7 post-BMT. (H) Percent and number of Rorgt⁺ Th17 cells on day 7 post allo-HCT. All comparisons in (A) to (H) were performed by two-tailed unpaired Mann-Whitney Test. Values are means ± standard deviation. *P < .05, **P < .01, ***P < .001, ****P < .0001, n = 5-15 mice per group. All results from two to three independent experiments.