Background：CCR6, also known as CD196/CCR6, is a chemokine receptor that is expressed on immature dendritic cells, B lymphocytes, and memory T cells. CCR6 binds CCL20, although members of the b defensin family also bind CCR6 with a lower affinity. CCR6 positive cells, and its ligand CCL20, have been detected in numerous organs, especially the secondary lymphoid organ. CCL20 is selectively made by the follicle-associated epithelium （FAE） overlying Peyers Patches （PPs） and isolated lymphoid follicles （ILFs）. CCL20 contributes to the recruitment of CCR6-expressing B cells to these structures. In humans, CCR6 can function to mediate arrest of T cells on dermal endothelial cells and is highly expressed on T cells resident in both normal and psoriatic skin. CCR6 and/or CCL20 have been implicated in the pathogenesis of rheumatoid arthritis and inflammatory bowel disease. Human T cells that are able to produce IL-17 express CCR6. It suggests that CCL20 and CCR6 have a role in inflammatory diseases by recruiting Th17 cells to target tissues.
