Intestinal epithelial cell regulation of macrophage and lymphocyte interleukin 10 expression

The intestinal mucosa is subject to daily antigenic challenge and to injury by proinflammatory cytokines. Interleukin 10 (IL-10) is an important anti-inflammatory cytokine produced by macrophages and lymphocytes that modulates this response.

To investigate the hypothesis that intestinal epithelial cells are a significant local source of IL-10 in the gut milieu and also participate in the regulation of macrophage and lymphocyte IL-10 expression in the intestinal microenvironment.

C-205 cells, a human intestinal epithelial cell line, were cultured for 2 days; lipopolysaccharide or tumor necrosis factor was then added. Media and cells were harvested at specific time points to determine the kinetics of IL-10 expression. C-205 cells were then cocultured with macrophages or lymphocytes isolated from human peripheral blood mononuclear cells, and IL-10 expression was assessed in unstimulated and stimulated conditions. Interleukin 10 protein was measured by enzyme-linked immunosorbent assay; IL-10 gene expression was measured by reverse transcriptase-polymerase chain reaction.

Constitutive production of IL-10 protein by C-205 cells was maximal at 3 days, paralleled by a peak in IL-10 messenger RNA (mRNA) expression at 24 hours. Lipopolysaccharide or tumor necrosis factor strikingly up-regulated IL-10 mRNA and protein expression by C-205 cells. Coculture of C-205 cells with macrophages or lymphocytes significantly increased lipopolysaccharide-stimulated IL-10 protein and mRNA release compared with C-205 cells, macrophages, or lymphocytes cultured alone.

Enterocytes are a responsive source of IL-10 and may play a role in modulating production of this important cytokine by the local inflammatory cells of the gut. These redundant mechanisms to augment IL-10 production suggest a central role for this cytokine in regulation of the local intestinal inflammatory response.