The interplay between intestinal immune cells and gut microbes protects the intestine and prevents excessive tissue damage due to inflammatory immune responses, reports a study published online this week in Nature Immunology.
Although we are born with a sterile gut, beneficial bacteria and other microbes soon colonize, which necessitates a symbiotic relationship with these gut inhabitants. Gerard Eberl and colleagues show newborn or germ-free mice have innate immune cells that express abundant amounts of the immune molecule IL-22 in their gut. IL-22 induces the production of antimicrobial substances by cells lining the gut, a process that is blocked upon bacterial colonization by the production of another immune molecule, IL-25.
Intestinal damage, as can occur upon infection with gut pathogens or ingestion of toxic chemicals, activates IL-22 expression and production of antimicrobial proteins and speeds recovery to a ‘calm’ gut.