A peripheral blood flow assay using CCR4+, CCR6+, and CCR10+ as Th22 cell surface markers showed that Th22 cells of patients with RA were significantly increased compared with that in the healthy control group; after methotrexate and leflunomide treatment, the peripheral Th22 cell levels were decreased in patients with RA (69). Here, CCR4 is linked to rheumatoid arthritis.