IL-22 deficiency exacerbates thymic GVHD. WT or Il22^−/− BALB/c recipients (H-2^d) were transplanted with 5 × 10⁶ B6 TCD BM (H-2^b) cells and 1 × 10⁶ WT B6 T cells. (A) Total thymic cellularity (n = 10-14 per group) and (B) number of CD4⁺CD8⁺ donor BM-derived DP cells (n = 5 per group) 21 days post-BMT. (C) Proportion of thymocyte subsets shown on the left, and MHCII⁺EpCAM⁺ TECs gated on viable CD45^– cells shown on the right. (D) Total number of cTECs and mTECs (n = 5-9 per group). Bar graphs represent mean ± SEM of at least 2 independent experiments. **P < .01.