While CCL20 expression was predominantly observed in mucosa associated lymphatic tissue (MALT), other lymphatic tissues, lung and liver tissues[9-11], its expression is virtually not detectable in spleen or bone marrow[12,13].CCL20 expression has further been demonstrated in inflammation related cells such as endothelial cells[14,15], neutrophils, natural killer (NK) cells, Th17 cells, B-cells and a variety of other immune cells[13,20] as well as in normal tissue of the colon, pancreas, stomach, prostate, testis, uterine cervix and skin.Here we review the literature on expression patterns of CCL20 and CCR6 and their physiological interactions as well as the currently presumed role of CCL20 and CCR6 in the formation of CRC and the development of liver metastasis, providing a potential basis for novel treatment strategies.
However, there are some members in the chemokine family which possess both inflammatory and homeostatic functions (Table To date, 20 different chemokine receptors have been characterized, which share many common structural features.
They are composed of approximately 350 amino acids that are divided into a short and acidic N-terminal end, seven helical transmembrane domains with three intracellular and three extracellular hydrophilic loops and an intracellular C-terminus containing serine and threonine residues that act as phosphorylation sites during receptor regulation.
Yamazaki et al reported that lack of CCR6 in Th17 cells inhibits their own as well as Treg recruitment into inflammatory tissues, reasoning that CCR6 deficiency in T cells decreases the susceptibility to autoimmune diseases.
Among many other functions, the CCL20 and CCR6 system also plays an important and again tightly regulated physiological role in the colonic mucosa.
Early after its discovery, CCR6 was found to function in part as a key mediator linking i DCs to adaptive immune responses.