IL21 and Hematochezia: After DSS induction, the mice with colitis showed significant weight loss, hematochezia, and an increase in disease activity index score; colonic shortening, epithelial erosion of the colonic mucosa on microscopic examination, formation of ulcers and granulation tissue, disorganized crypt structure, and inflammatory cell infiltration; and a significant increase in the levels of proinflammatory cytokines IL-7, IL-15, and IL-21 in colonic tissues.