Mucosal Immunology Laboratory, Massachusetts General Hospital, 114 16th Street (114-3503), Charlestown, MA 02129-4404, USA. wwalker@partners.org
Indigenous intestinal microbes have co-evolved with the intestinal immune system to form a symbiotic ecosystem. In the postnatal period, intestinal microbes provide the developing gut with stimuli that are necessary for healthy maturation of the intestinal immune system. Cross talk between the host and commensal microbes is an essential component of gut homeostasis mechanisms also in later life. During recent years, innovative research has shed light on the molecular mechanisms of these interactions.