Interactions between epithelial cells and immune cells in the intestine.

Not merely a passive barrier as previously assumed, epithelial cells act as sensitive indicators of infection that initiate defense responses. Noninvasive as well as invasive organisms have been demonstrated to elicit production of chemoattractants. That noninvasive organisms have this capacity suggests that receptor-mediated signaling pathways may be involved. Epithelial cells have been found to release both chemokines and cytokines in a precise mixture that varies according to the origin or maturity of the cell. Different microorganisms also elicit different response patterns. The information presented provides a basis for a new view of epithelial cell function in relation to host defense.