Innate immune responses of epithelial cells following infection with bacterial pathogens

The ability to discriminate between pathogenic and nonpathogenic bacteria i s extremely important for epithelial cells lining mucosal surfaces and is p articularly so in colonic epithelial cells. Accumulating evidence suggests that bacterial recognition systems used by epithelial cells are very differ ent from those in cells of the myeloid lineage and are likely to have devel oped to maintain mucosal surfaces in a state of homeostasis with the normal microbial flora. Bacterial invasion of epithelial cells or breach of the e pithelial barrier provides a signal to epithelial cells to initiate inflamm atory responses, which are key events for the clearance of the infecting mi crobe. Therefore, elucidation of the mechanisms by which epithelial cells r ecognize bacteria and bacterial products, and of the nature of the innate i mmune responses that are triggered by these factors are important for our u nderstanding of both the immunology of mucosal surfaces and bacterial patho genesis.