Infiltration of peroxidase-producing eosinophils into the lamina propria of patients with ulcerative colitis.

Little information is available to explain the pathogenesis of ulcerative colitis (UC). In this study, we focused on eosinophils in the lamina propria of the mucosa of patients with UC in the active phase. Biopsy specimens were taken from 17 patients with UC in the active phase, 17 in the inactive phase, and 20 control patients, and submitted for histochemical staining for peroxidase and chloroacetate esterase for microscopic examination. Both peroxidase-producing and chloroacetate esterase-producing cells in the lamina propria increased markedly in the active phase (8.3 +/- 3.1/0.01 mm2 and 6.6 +/- 2.7/0.01 mm2, respectively), compared with values in the inactive phase (0.8 +/- 0.6/0.01 mm2 and 1.3 +/- 0.6/0.01 mm2) or in the controls (1.3 +/- 0.8/0.01 mm2 and 1.3 +/- 0.4/0.01 mm2). Triple staining for peroxidase, chloroacetate esterase, and nonspecific esterase in the specimens revealed that the peroxidase-producing cells constituted a different population from that of neutrophils, macrophages/monocytes, or basophils. A monoclonal antibody specific for eosinophil peroxidase stained almost all infiltrated peroxidase-producing cells. These results indicated that eosinophils with strong peroxidase activity had infiltrated the lamina propria in UC, suggesting an allergic background and the involvement of released peroxidase in the mucosal damage characteristic of UC.