Innate Immunity at Mucosal Surfaces

Mammalian mucosal surfaces form critical interfaces between the bodily tissues and foreign antigens such as commensal flora and ingested food. Innate mucosal immunity in the gut, as represented by intestinal barrier functions and germline-encoded pattern recognition receptor (PRR)-mediated immune responses, plays an important role in regulating intestinal health and in disease prevention. Intestinal epithelial cells not only function as physical barriers, but also participate in innate immune responses. Disrupted epithelial cell function in the gut can lead to intestinal disorders. Additionally, PRR gene defects, including those relating to toll-like receptors, C-type lectin receptors, retinoic-acid-inducible gene-I-like receptors, and NOD-like receptors, lead to mucosal dysfunction and the subsequent induction of intestinal inflammation. In this chapter, we focus primarily on the current understanding of the role played by innate immunity at mucosal surfaces as an intestinal barrier system and how PRRs relate to such immunity.