Despite its pivotal role in mucosal inflammation, data on TNFα levels in inflammatory bowel diseases have been contradictory.

To examine TNFα production in relation to the type and severity of inflammation and therapy, using colonic explant cultures.

Rectal mucosal biopsies from 271 paediatric patients (178 inflammatory bowel disease, 27 inflammatory controls, 66 normal) were cultured for 4 or 18 h. Basal TNFα tissue content and release into the medium were measured by ELISA and compared to histological severity and clinical parameters.

TNFα release as well as tissue‐associated TNFα levels were significantly increased in rectal biopsies from involved inflammatory bowel disease tissue. The amount of TNFα correlated with inflammation severity scores. TNFα levels were higher at 18 compared to 4 h in all groups, whether inflamed or not. TNFα released from rectal biopsies was lower among treated patients at 18 h. The presence of proximal colonic involvement was associated with higher TNFα release by uninvolved Crohn’s disease rectal biopsies compared to patients with ileitis alone.

TNFα production and release is increased in involved rectal explants from inflammatory bowel disease. Anti‐inflammatory treatment diminishes this response.