IL17A and colitis: In addition, transfer of MDSC significantly elevated IL17A level in TH17 cells in PP and mLN of colitic ArgmyeKO mice (Figures 5D,F), while IL-17F level was reduced and eventually prolonged survival of colitic ArgmyeKO mice (Figures 5E,G), indicating a key role of MDSC-derived Arg-1 in regulating TH17 cells and controlling colitis progression in ArgmyeKO.