Intestinal Epithelial Cell-Derived Interleukin-7 as a Regulatory Factor for Intestinal Mucosal Lymphocytes

Publisher Summary Recent studies have demonstrated that interactions between mucosal lymphocytes and intestinal epithelial cells are crucial for maintaining mucosal immunity. The mucosal lymphocytes may serve a critical role in the mucosal immune system by providing immune surveillance of epithelial cells. Although recent studies have shown that cytokines released from mucosal mononuclear cells may affect intestinal epithelial cell differentiation, the signals originating from epithelial cells that may regulate mucosal lymphocytes are yet to be defined. It has been reported that mucosal lymphocytes proliferate minimally to mitogens or stimulation through the CD3 pathway. This in vitro hyporesponsiveness of mucosal lymphocytes is supposed to be due to the absence of essential growth factor. Interleukin-7 (IL-7) is a stromal cell-derived pleiotropic cytokine with lymphoid precursor cell growth-promoting activity. The recent studies have demonstrated IL-7 mRNA expression and IL-7 protein production in the intestinal epithelial cells. These results, in concert with the findings that IL-7 receptors are expressed by mucosal lymphocytes, suggest that IL-7 regulates the proliferation of the intestinal mucosal lymphocytes. This chapter reviews the intestinal epithelial cell-derived IL-7 as a regulatory factor for the intestinal mucosal lymphocytes.