CCR4 and rheumatoid arthritis: Tregs isolated from the synovial fluid of RA patients express higher levels of CCR4, CCR5 and CXCR444, which together have a multitude of chemokine ligands (including CCL17, CCL22, CCL16, CCL3, CCL3L1, CCL4, CCL5, CCL14 and CXCL1248), some of which are established to be produced by FLS45.