Objectives and methods: We previously reported the increased contents of group II phospholipase A2 (PLA2) in inflamed colonic mucosa of patients with Crohn's disease and ulcerative colitis (UC). However, the cellular source of the increased group II PLA2 has remained to be clarified. In the present study, we examined immunohistochemical localization of group II PLA2 in inflamed colonic mucosal biopsy samples obtained from eight patients with Crohn's disease, seven with UC, and in normal colonic mucosa of six control subjects without inflammatory bowel disease using a monoclonal antibody raised against human group II PLA2.
Conclusions: On immunoblot analysis using the antibody, a single band was detected on each lane containing colonic mucosal homogenates from a control subject, a Crohn's disease patient, or a UC patient at the same position as human group II PLA2 purified from ileal mucosa. The results of immunohistochemistry showed that colonic epithelial cells in inflamed mucosa obtained from all active Crohn's disease patients examined (n = 4) contained immunoreactive group II PLA2. In four of seven patients with active UC, group II PLA2 immunoreactivity was similarly positive. No apparent group II PLA2 immunoreactivity was detected in all colonic mucosal biopsy samples obtained from inactive Crohn's disease patients (n = 4) and control subjects. The present study supports the presence of group II PLA2 in colonic epithelial cells in actively inflamed mucosa of patients with Crohn's disease and UC, which suggests that epithelial cells may serve as the cellular source of increased group II PLA2 content in inflamed colonic mucosa of these patients.