Since M2 macrophages derived from M1 macrophages improve the resolution of inflammation and aid wound healing18, our results suggest that IL-33 ameliorates colitis via the modulation of macrophages, not of T-cells and, notably, Treg and Th2 cells are dispensable for IL-33-mediated amelioration of colitis in our system, similar to that of a recent studies14, 53. Here, IL33 is linked to colitis.