Commeusal bacteria shapes gut immune system through epigenetic modifications

The mammalian fetus is maintained under sterile conditions in the uterus. However, immediately after birth, it is exposed to a multitude of environmental microbes, some of which colonize the skin and mucosal surfaces. Particularly, the lumen of the human distal intestine harbors trillions of commensal bacteria. The colonization of bacteria contributes the promotion of the development of gut-associated lymphoid tissue, which is an inductive site for mucosal immune responses. On the other hand, aberrant immune responses to commensal bacteria cause the development of pathogenic inflammatory disorders. To avoid this risk, the intestinal mucosa has a large number of regulatory T (Treg) cells, which play a pivotal role in the containment of inflammatory responses. In this article, we introduce the role of commensal bacteria and their metabolites in the maintenance of Treg homeostasis in the colonic lamina propria.