SULFHYDRYL BLOCKER-INDUCED COLITIS IN THE RAT - IMMUNOLOGICAL CHANGESIN THYMUS GLAND AND COLONIC MUCOSA

The study was designed to examine the changes of thymus in sulfhydryl blocker-induced colitis. We used N-ethylmaleimide (NEM) as sulfhydryl blockers. Fasted male Sprague-Dawley rats were given 3% NEM in 1% meth yl cellulose into the colon. N-ethylmaleimide treatment caused severe diarrhoea with bleeding for the first 7 days. At autopsy, adhesions, c olon dilatation, and single or multiple erosions and ulcers were obser ved. Time-course studies revealed that the lesions were most extensive and severe 3 or 7 days after the administration of NEM. Histological examination of colon on the 3rd day after NEM treatment demonstrated m ucosal erosion, oedema and extensive infiltration of neutrophils. The mucosal lesions extended into the submucosa and muscle on the 7th day after NEM treatment. Immunohistochemical studies showed that T cells a nd macrophages were markedly increased in the lamina propria of coloni c mucosa. After 3 weeks, the infiltration of chronic inflammatory cell s was observed and regeneration of the mucosa was noticed. The thymus gland was significantly decreased in weight and size on the 3rd day af ter NEM treatment, but the weight loss of thymus gland was regained in 3 weeks. Transient atrophy of thymus gland was noticed in this coliti s model. The phenotypes of thymocytes were not influenced by NEM treat ment. It is concluded that the thymus abnormalities in human ulcerativ e colitis are not induced in this animal model and that other chronic models are necessary for the elucidation of the immunological abnormal ities, including thymus abnormalities.