AIM: To produce an antibody against rat eosinophil cationic protein (ECP) and to examine the effects of the antibody in rats with dextran sulfate sodium (DSS)-induced colitis.METHODS: An antibody was raised against rat ECP. Rats were treated with 3% DSS in drinking water for 7 d and received the antibody or normal serum. The colons were exarmined histologically and correlated with clinical symptoms.Immunohistochemistry and Western blot analysis were estimated as a grade of inflammation.RESULTS: The ECP antibody stained the activated eosinophils around the injured crypts in the colonic mucosa.Antibody treatment reduced the severity of colonic ulceration and acute clinical symptoms (diarrhea and/or blood-stained stool). Body weight gain was significantly greater and the colon length was significantly longer in anti-ECP-treated rats than in normal serum-treated rats. Expression of ECP in activated eosinophils was associated with the presence of erosions and inflammation. The number of Ki-67-positive cells in the regenerated surface epithelium increased in anti-ECP-treated rats compared with normal serum-treated rats. Western blot analysis revealed reduced expression of macrophage migration inhibitory factor (MIF) in anti-ECP-treated rats.CONCLUSION: Our results indicate that treatment with ECP antibody, improved DSS-induced colitis in rats, possibly by increasing the regenerative activity of the colonic epithelium and downregulation of the immune response,and suggest that anti-ECP may promote intestinal wound healing in patients with ulcerative colitis (UC).