How vitamin A metabolizing dendritic cells are generated in the gut mucosa

CD103(+) dendritic cells (DCs) represent the major migratory DC population in the intestinal lamina propria and are believed to play an essential role in the initiation and regulation of mucosal adaptive immune responses. Small intestine (SI) CD103(+) DCs have an enhanced capacity to generate the vitamin A metabolite, retinoic acid, a property that underlies their ability to induce the gut homing receptors CC chemokine receptor 9 and a4ß7 on responding T and B cells, and enhance forkhead box P3(+) T regulatory and IgA plasma cell differentiation in vitro. In this review, we discuss the environmental signals that appear to promote vitamin A metabolising activity in SI CD103(+) DCs in the steady state and thus which may contribute to driving the unique nature of SI immune responses.