Ccl22-deficient mice are highly susceptible to DSS-induced colitis. Ccl22^−/− and WT C57BL/6 mice were fed with or without 0.5% DSS dissolved in tap water over a period of 1 wk followed by 1 wk of recreation, in three consecutive cycles. Disease severity was analyzed at day 7 after the last cycle of DSS administration. (A) Loss of body weight, diarrhea, and the presence of occult or overt blood in the stool was used to determine the clinical disease activity index (DAI). (B–D) The colon length was measured (B) and tissue sections of the colon were analyzed for mononuclear and neutrophilic cell infiltration, crypt hyperplasia, epithelial injury, and crypt abscesses (C and D) to determine the histological score (bars, 200 µm). Data are shown as mean ± SEM of five mice per group and are representative of three independent experiments. ***, P < 0.001 (two-sided Student’s t test).