Location of nitroblue tetrazolium-reducing activity in human colonic mucosa obtained by biopsy

The location of nitroblue tetrazolium-reducing activity was studied in colonic biopsy specimens from 28 patients with ulcerative colitis and from 23 controls. Nitroblue tetrazolium was reduced by epithelial cells, vascular endothelium, and interstitial mononuclear cells of the colonic mucosa from both groups. Blue formazan, a reduced form of nitroblue tetrazolium, was seen faintly after 30 min of culture; the amount increased up to 2 hr tested. The vascular endothelium of the patients with ulcerative colitis reduced nitroblue tetrazolium significantly more than that of the controls. The reduction of nitroblue tetrazolium was graded from 0 to 3 and was 1.0 +/- 0.6 in the controls, 1.6 +/- 0.8 in ulcerative colitis patients (P < 0.05), 1.9 +/- 0.7 (P < 0.01) in patients with active ulcerative colitis, and 1.4 +/- 0.9 in patients with inactive ulcerative colitis (difference not significant). Aggregates of mononuclear cells that reduced nitroblue tetrazolium were found in 10 of 28 patients with ulcerative colitis but not in the controls.