IRF5 and systemic lupus erythematosus: Although the molecular mechanism of Th1/Th2 shift in our present study is not investigated, it is reported that the TLR7 downstream signal molecule interferon regulatory factor (IRF) 5 can regulate class switching from IgG1 to IgG2a in B cells [12], while IRF5-deficient mice are protected from pristane-induced lupus via increased Th2 cytokines and altered IgG class switching [13].