The increase in IRF5 expression after activation with anti-IgM, anti-CD40, and R848 in vitro suggested the possibility that IRF5 might be increased in GC B cells in FcγRIIB−/−Yaa mice in vivo, because TLR7 activation is thought to be important for spontaneous GC formation in other lupus models (50). Here, IRF5 is linked to systemic lupus erythematosus.