IL17A and rheumatoid arthritis: Rheumatoid arthritis (RA) is an autoimmune disease with polarization disorder toward Th1 and Th2 that produces proinflammatory cytokines such as IL-1β, IL-6, IL-17, TNF-α, IFN-γ and IL-8 and, as a result, causes an inflammatory state in the body.52-54 Patients with RA have very low levels of cytokines secreted by Th2 lymphocytes.52 All of these events lead to involvement and destruction of the joints.