IL17A and rheumatoid arthritis: Pro-inflammatory cytokines, which include, IL-1β, TNF-α, IL-7, IL-6, IL-17, IL-15, IL-23, IL-18, interferon-gamma (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF), play a key role in the modulation of the inflammation process implicated in the mechanisms of RA which are summarized in Figure 1.