CCL2 and rheumatoid arthritis: Stimulation of RA-FLS with CCL2 and CCL5 can enhance the production of IL-6 and CXCL8 [40], while CCL2, CXCL10, CCL5 and CXCL9 induce the gelatinase and collagenase activities in the supernatants of cultured FLS [41].