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. Here, CCL17 is linked to rheumatoid arthritis.