IL21 and systemic lupus erythematosus: Conditional targeting of the transcription factor T-bet, which is necessary and sufficient for ABC formation,4,16 in B cells, improves the overall health status of SLE mice, including improved kidney function, better survival rates, reduction of autoantibodies and reduced titres of serum IgG2a.34 Thus, in a similar way, we believe that the prevention of ABC formation (for example, via targeting and/or enhancing molecules involved in the SWEF-IRF5-IL-21 pathway) may be beneficial and have a therapeutic effect in patients with SLE (Figure 1).