IL17A and rheumatoid arthritis: Though most Th17 cells did not simultaneously express both IL-22 and IL-17, the percentage of CD4+IFNγ-IL17+IL-22+ T cells was significantly increased in AS (0.63±0.34%)) and RA (0.65±0.29%) patients compared with OA patients (0.20±0.04%) and healthy controls (0.19±0.05%)(Fig. 1b).