IL21 and rheumatoid arthritis: We overviewed the cytokines and molecules involved, starting from RF and ACPA, which represent the cornerstone autoantibodies operating in RA, and examined the diverse roles of cytokines such as TNF-α, IL-6, IL-7, IL-17, IL-21, IL-23, IL-1β, IL-18, IL-33, GM-CSF, and IL-2.