INTESTINAL EPITHELIAL-CELL REGULATION OF MACROPHAGE AND LYMPHOCYTE INTERLEUKIN-10 EXPRESSION

Background: The intestinal mucosa is subject to daily antigenic challe nge and to injury by proinflammatory cytokines. Interleukin 10 (IL-10) is an important antiinflammatory cytokine produced by macrophages and lymphocytes that modulates this response. Objective: To investigate t he hypothesis that intestinal epithelial cells are a significant local source of IL-10 in the gut milieu and also participate in the regulat ion of macrophage and lymphocyte IL-10 expression in the intestinal mi croenvironment. Methods: C-205 cells, a human intestinal epithelial ce ll line, were cultured for 2 days; lipopolysaccharide or tumor necrosi s factor was then added. Media and cells were harvested at specific ti me points to determine the kinetics of IL-10 expression. C-205 cells w ere then cocultured with macrophages or lymphocytes isolated from huma n peripheral blood mononuclear cells, and IL-10 expression was assesse d in unstimulated and stimulated conditions. Interleukin 10 protein wa s measured by enzyme-linked immunosorbent assay; IL-10 gene expression was measured by reverse transcriptase-polymerase chain reaction. Resu lts: Constitutive production of IL-10 protein by C-205 cells was maxim al at 3 days, paralleled by a peak in IL-10 messenger RNA (mRNA) expre ssion at 24 hours. Lipopolysaccharide or tumor necrosis factor strikin gly up-regulated IL-10 mRNA and protein expression by C-205 cells. Coc ulture of C-205 cells with macrophages or lymphocytes significantly in creased lipopolysaccharide-stimulated IL-10 protein and mRNA release c ompared with C-205 cells, macrophages, or lymphocytes cultured alone. Conclusions: Enterocytes are a responsive source of IL-10 and may play a role in modulating production of this important cytokine by the loc al inflammatory cells of the gut. These redundant mechanisms to augmen t IL-10 production suggest a central role for this cytokine in regulat ion of the local intestinal inflammatory response.