Dextran sodium sulphate (DSS) induced colitis is commonly used to simulate human ulcerative colitis (UC). However, the mucosal immune responses related to the severity of disease have not been comprehensively documented. We used different concentration of DSS, induced various severities of colitis, and simultaneously examined the frequency of immune cells, antibodies and cytokine production. We found that T regulatory cells (Tregs), B cells, and IgA secretion increased on the recovery phase of mild colitis, accompanied by CD11b(+) cells, interleukin (IL)-6 and tumor necrosis factor (TNF)-α accumulated mildly. While during severe and irreversible colitis, the CD11b(+) cells, IL-6, and TNF-α infiltrated severely with Tregs, B cells, and IgA increased inconspicuously. These results demonstrate that Tregs, B cells, and IgA may play a significant role in maintaining the homeostasis of gut, by suppressing CD11b(+) cells and the pro-inflammatory cytokines.