The effects of pleuran, ß-1,3 glucan isolated from Pleurotus ostreatus, were studied in a model of acute colitis induced by intracolonic administration of acetic acid. There was a reduction of the colonic damage score, colonic wet weight and wet/dry weight ratio 48 h after single luminal 2 % pleuran suspension pretreatment. Similar results were obtained after repeated intraperitoneal administration of pleuran in doses of 30 and 100 mg/kg. Pleuran given orally as a 10 % food component over 4 weeks was effective in reducing the extent of mucosal damage, but did not prevent the increase of myeloperoxidase in the injured colonic segment. In the segment without macroscopic evidence of inflammation, myeloperoxidase activity was significantly lower as documented by histological examination. The results indicate a possible role of this immunomodulator in the treatment of ulcerative colitis., V. Nosáľová, P. Bobek, S. Černá, Š. Galbavý, S. Štvrtina., and Obsahuje bibliografii