STAT5A and systemic lupus erythematosus: In the MRLlpr murine model of SLE, many alterations in cytokine signal transduction were noticed during progression of the disease, including impairment of STAT1 signaling in response to IFNα, IFNγ, IL-6, and IL-21, STAT3 signaling in response to IL-6, STAT5 responses to IL-15 and STAT6 responses to IL-4.