IN-SITU EXPRESSION OF INTERLEUKIN-10 IN NONINFLAMED HUMAN GUT AND IN INFLAMMATORY BOWEL-DISEASE

A dysregulated secretion of contra-inflammatory cytokines such as inte rleukin-10 (IL-10) could play a role in the pathogenesis of inflammato ry bowel disease (IBD). Vile have investigated the expression of IL-10 in gut tissues from patients with Crohn's disease (CD), ulcerative co litis (UC) and controls by mRNA in situ hybridization and immunohistoc hemistry. Intestinal epithelial cells were found to express IL-10 mRNA and IL-10 protein in all of the tissues investigated without any majo r differences in the expression patterns. However, compared with nonin flamed gut, significantly increased numbers of mononuclear cells (MNCs ) producing IL-10 were present in inflamed gut, both in CD and UC. Thi s cytokine was expressed most prominently by inflammatory infiltrates enriched in macrophages, although T cells seem to contribute to its pr oduction as well. Elevated IL-10 expression in IBD was mainly detected in the submucosa, whereas IL-10 production by lamina propria cells re mained comparably low. In contrast, the expression of IL-1 beta mRNA w as preferentially increased in the lamina propria. Our data argue agai nst a general deficiency in IL-10 production in IBD. The results sugge st rather that the local production of IL-10 by mucosal MNCs in IBD is insufficient to down-regulate pro-inflammatory cytokines such as IL-1 beta in the lamina propria compartment.