Regulation of intestinal homeostasis by dendritic cells.

The healthy gut consists of the commensal flora, the epithelial layer, and the gut-associated lymphoid tissues (GALT). The GALT need to be hyporesponsive to commensal and dietary antigens while possessing the capacity to detect and attack pathogens. Accumulating evidence suggests that dendritic cells (DCs) play integral roles in managing this paradoxical situation and maintaining the complex homeostasis in the gut, which includes the induction of immunoglobulin A (IgA) synthesis. This review outlines the roles of the commensal flora, epithelial layer, and GALT in mucosal homeostasis and inflammatory conditions and highlights recent progress in our understanding of how DCs are involved in IgA synthesis in the gut.