CCL2 and rheumatoid arthritis: Apart from Th17, Th1 and CXCR3+ Th2 phenotypes are the main subtypes of T helper cells in the synovium of patients with RA; IL-4 and IL-13 induce FLS to produce a series of inflammatory cytokines, such as IL-6, CCL2, CXCL1, and CXCL8, whereas IFNγ promotes the expression of CXCL10 (32).