Microbiota-derived metabolites in intestinal immune disorders.

The gastrointestinal tract features a complex barrier system against luminal microorganisms and dietary antigens to avoid initiation of pathological inflammatory responses in the lamina propria. The intestinal microbiota plays an important role in shaping host immune systems and reinforcing epithelial barrier integrity. Alterations in microbial communities are observed in patients with chronic inflammatory disorders, including inflammatory bowel disease (IBD). Although the etiology of IBD ramains unclear, accumulating evidence suggests that a dysbiotic microbiota is involved in the onset and/or progression of IBD by modulating host immune systems and the epithelial barrier through microbial components and microbially-derived metabolites, together with host genetics. Therefore, a detailed understanding of the interactions between the intestinal microbiota, epithelial cells, immune cells, and host genetic variants under homeostatic and inflammatory conditions may advance therapeutic approaches for IBD.