INTERLEUKIN-15 ACTIVITY IN THE RECTAL MUCOSE OF INFLAMMATORY BOWEL-DISEASE

Background & Aims: Interleukin (IL)-15 has been found to shave many im munoregulatory activities in lymphocytes with IL-2. The aim of this st udy was to investigate IL-15 activity in organ cultures, localization of IL-15 messenger RNA (mRNA), and proliferation of lamina propria mon onuclear cells (LPMCs) in response to recombinant IL-15 using the muco sal tissues obtained from patients with inflammatory bower disease (IB D). Methods: The contents of IL-15, tumor necrosis factor alpha, and I L-2 in the culture supernatant of the rectal mucosal tissues were dete rmined by an enzyme-linked immunosorbent assay. Expression of IL-15 mR NA was analyzed by in situ hybridization, and proliferative response o f LPMCs to recombinant IL-15 was determined by [H-3]thymidine incorpor ation into DNA. Results: Significantly greater IL-15 activity was dete cted in active IBD, and this elevation was also observed in inactive u lcerative colitis. In contrast, greater tumor necrosis factor a activi ty was observed only in active IBD, and IL-2 was not detected in organ cultures. In situ hybridization showed IL-15 mRNA in macrophages and epithelial cells in active IBD specimens, and recombinant IL-15 induce d a dose-dependent proliferative response in LPMCs. Conclusions: Mucos al IL-15 may be involved in the pathogenesis of IBD as one of the impo rtant mediators in activation of mucosal immune cells.