Host Defense Peptides as Innate Immunomodulators in the Pathogenesis of Colitis

Abstract Infectious colitis and inflammatory bowel diseases are common devastating diseases causing pain, diarrhea, and death. Innate immune defenses in the intestine, mostly contributed by host defense peptides, including cathelicidins and defensins, are still not fully understood. Of particular interest is to comprehend the function of cathelicidins and defensins in the pathogenesis of colitis and their contribution to intestinal host-microbial defenses. Aspects of the pathogenesis of infectious colitis studied in this chapter uncover roles of cathelicidins and defensins that promote epithelial defenses, regulate inflammatory responses, and mobilize leukocytes across the intestine for microbial elimination. This may decode how the innate system intends to quickly restore gut homeostasis and avoid damaging inflammation associated with pathogen persistence. Understanding these functions of host defense peptides in intestinal defenses facilitates developing therapeutic alternatives to control infectious diseases (e.g., enterocolitis) and mitigates inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis.