IL21 and rheumatoid arthritis: Here we review several of these cytokines, including TNF-α, IL-6, IL-7, IL-17, IL-21, IL-23, IL-1β, IL-18, IL-33, granulocyte macrophage colony-stimulating factor (GM-CSF), and IL-2, which are known to be active from the acute to the chronic stage of RA, and may have potential for therapeutic targeting [11,12].