ARG1 and colitis: Transfer of WT-derived MDSC alleviated colitis progression in ArgmyeKO mice evidenced by reversed weight loss of colitic ArgmyeKO mice, and IL-17A level significantly increased in PP and mLN of ArgmyeKO mice, indicating a key role of MDSC-derived Arg-1 in regulating TH17 cells and controlling colitis progression in ArgmyeKO mice.