Epithelial cell contributions to intestinal immunity.

The epithelial surfaces of the mammalian intestine interface directly with the external environment and thus continuously encounter pathogenic bacteria, fungi, viruses, and parasites. The intestinal epithelium is also closely associated with complex communities of symbiotic microorganisms. Intestinal epithelial cells are thus faced with the unique challenge of directly interacting with enormous numbers of microbes that include both pathogens and symbionts. As a result, gut epithelia have evolved an array of strategies that contribute to host immunity. This chapter considers the various mechanisms used by epithelial cells to limit microbial invasion of host tissues, shape the composition of indigenous microbial communities, and coordinate the adaptive immune response to microorganisms. Study of intestinal epithelial cells has contributed fundamental insights into intestinal immune homeostasis and has revealed how impaired epithelial cell function can contribute to inflammatory disease.