The gastrointestinal (GI) tract represents a unique challenge to the mammalian immune system. It must tolerate the presence of the luminal microbiota and thus not respond to their products, but still protect the intestinal mucosa from potentially harmful dietary antigens and invading pathogens. The intestinal epithelium, composed of a single layer of cells, is crucial for preserving gut homeostasis and acts both as a physical barrier and as a coordinating hub for immune defense and crosstalk between bacteria and immune cells. We highlight here recent findings regarding communication between microbes and intestinal epithelial cells (IECs), as well as the immune mechanisms employed by distinct IEC subsets to promote homeostasis, emphasizing the central and active role that these cells play in host enteric defense.
J.M.A. is supported by Canadian Institutes of Health Research (CIHR), Canadian Association of Gastroenterology (CAG), and Michael Smith Foundation for Health Research fellowships. S.M.C. is supported by a University fellowship and Mitacs. H.T.L. is supported by CIHR, CAG, and Mitacs. S.Y.C. and H.J.K. are supported by the National Research Foundation of Korea and the Korean Health Technology R&D Project. B.A.V. is supported by operating grants from the National Science and Engineering Research Council, CIHR, and Crohn\u2019s and Colitis Canada. B.A.V. is the Children with Intestinal and Liver Disorders (Ch.I.L.D.) Fdn Research Chair in Pediatric Gastroenterology.
