Besides IL-6 and TNF-α, different cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-17 (IL-17), interleukin-21 (IL-21), and interleukin-23 (IL-23) can play an important role in RA development and are potential factors that are also considered in current and future RA therapies [10]. Here, IL21 is linked to rheumatoid arthritis.