Since the Irf5 gene variants are strongly associated with serum IgG2a and IL-6 levels in patients with SLE [58], the specific binding of IRF5 within Il6 transcription start site (TSS), the Ighg2c region and Jun protein was observed in DKO B cells during IL-21 stimulation. This evidence concerns the gene IRF5 and systemic lupus erythematosus.