Host immune interactions in chronic inflammatory gastrointestinal conditions.

PURPOSE OF REVIEW: We performed a literature review of the latest studies on the interactions between the host immune system and microbes in chronic intestinal inflammatory conditions. RECENT FINDINGS: The mechanisms leading to celiac disease (CeD) and inflammatory bowel disease (IBD), the most common chronic inflammatory gastrointestinal conditions, are complex. The intestinal homeostasis depends on the interactions between the microbiota, the intestinal mucosa and the host immune system. Failure to achieve or maintain equilibrium between a host and its microbiota has the potential to induce chronic conditions with an underlying inflammatory component. Mechanisms by which intestinal microbes trigger inflammation include the alteration of intestinal permeability, activation of the host immune system and digestion of dietary antigens with a consequent repercussion on tolerance to food. Therefore, therapies modulating gut microbiota, including diet, antibiotics, probiotics and faecal transplantation have a potential in CeD and IBD. Probiotics are effective to treat pouchitis and faecal transplant for ulcerative colitis, but the evidence is less clear in Crohn's disease or CeD. SUMMARY: Diverse regulatory mechanisms cooperate to maintain intestinal homeostasis, and a breakdown in these pathways may precipitate inflammation. The role of microbiota inducing immune dysfunction and inflammation supports the therapeutic rationale of manipulating microbiota to treat chronic inflammatory conditions.