IL17A and rheumatoid arthritis: Th17 cell produce several cytokines including IL-17, IL-17F, IL-6, IL-21, IL-22 and tumor necrosis factor-alpha (TNF-α) that play a key role not only in the RA but also in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and collagen induced arthritis (CIA), and they induces dendritic cells (DCs) to produce IL-12 and interferon (IFN-c) [5,6,7,8,9,10].