IL21 and systemic lupus erythematosus: For instance, overexpression of IL-21 induces inflammation; in the BXSB.6-Yaa+/J mouse model of systemic lupus erythematosus (SLE), affected mice exhibit elevated levels of IL-21, whereas IL-21R−/−BXSB.6-YAA+/J mice do not develop SLE [67].