IL21 and systemic lupus erythematosus: In this context, BAFF, IL-6, and IL-21 affect B cell survival and differentiation while IL-2, IL-4, IL-6, IL-10, IL-18, IFN-α, IFN-γ, IL-17, IL-21, and IL-23 can modulate Th1/Th2 and Th17/Treg balance, and elevated levels of these cytokines have been observed in SLE, including patients with LN (19–27).