Bacterial-modulated host immunity and stem cell activation for gut homeostasis

Although it is widely accepted that dynamic cross-talk between gut epithelia and microorganisms must occur to achieve gut homeostasis, the critical mechanisms by which gut–microbe interactions are regulated remain uncertain. In this issue of Genes & Development, Buchon and colleagues (pp. 2333–2344) revealed that the reaction of the gut to microorganisms is not restricted to activating immune systems, but extends to integrated responses essential for gut tissue homeostasis, including self-renewal and the differentiation of stem cells. Further investigation of the connection between immune response and stem cell regulation at the molecular level in the microbe-laden mucosal epithelia will accelerate our understanding of the regulatory mechanisms of gut homeostasis and of the pathogenesis of diseases such as chronic inflammatory diseases and colorectal cancers.