That is, a substantial population of IFN-γ+ T cells in SF has been reported to co-express CCR6 and CD161, the surface markers of human Th17 cells, and therefore, Th17 cells may be converted to a Th1-like phenotype via an intermediate state of IFN-γ+ IL-17+ T cells when they encounter an IL-12high environment, which is seen in SF of RA and JIA (44, 45). This evidence concerns the gene IL17A and rheumatoid arthritis.