CCR6 and CCL20: emerging players in the pathogenesis of rheumatoid arthritis.

The therapeutic targeting of pro-inflammatory TNF with neutralising biological anti-TNF agents, often in combination with other disease-modifying anti-rheumatic drugs, such as the purine synthesis inhibitor methotrexate has been the first major break-through in the treatment of chronic inflammatory diseases in decades. There are however, side effects and disadvantages of these treatments, such as general immunosuppression as well as therapy resistance in a large proportion of patients. This evokes the wish for other, more specialised forms of treatments. The targeting of chemokines and their receptors to disrupt cell movement specifically has been seen as a promising avenue of therapy for a considerable time. We will discuss one particular chemokine and its receptor, the C-C chemokine ligand CCL20 and the C-C chemokine receptor CCR6, and summarise its genetic and biological role in rheumatoid arthritis (RA). CCR6 has been associated with RA in genome-wide association studies and has been shown to be an interesting candidate for a therapeutic approach, considering its and CCL20's expression patterns within the tissue as well as the immune system.