The role of epithelial cells in immune regulation in the gut.

A variety of mechanisms contribute to the ability of the gut to either react or remain tolerant to antigens present in the intestinal lumen. Intestinal epithelial cells can control the uptake, transmission and presentation of luminal antigens through an astonishingly diverse set of pathways. Antigens can cross the epithelial barrier via non-specific pinocytotic, specific receptor mediated, or intracellular/paracellular bypass pathways. The differential processing and presentation by a variety of restriction elements may result in the activation of functionally distinct target cell populations which have the capacity to regulate the predominant trend of immune unresponsiveness within the gut. Copyright 2001 Academic Press.