In SLE, T cells undergo an aberrant hyperactivation that induces the excessive production of several cytokines such as Interleukin (IL)-17, tumor necrosis factor (TNF), interferon (IFN)-γ and IL-21, which are involved in the induction of tissue damage, the recruitment of inflammatory cells to affected tissues and the co-stimulation of B cells. Here, IL21 is linked to systemic lupus erythematosus.