IL17A and rheumatoid arthritis: In rheumatoid arthritis, Th1 cytokines such as TNF-α, IFN-γ, IL-1, IL-12 and IL-18, as well as IL-23/IL-17 axis, contribute to joint inflammation, cell infiltration and destruction [62-68]; there also appears to be a compensatory anti-inflammatory response in synovial membrane, suggesting a protective role of Th2 cytokines [62].