The results of the present study demonstrated that LAG3+ Treg suppress thedevelopment of GCB andTFH, antibody production and disease progression in lupus-proneMRL/lpr mice.TGF-β3, which isproduced by LAG3+Treg in Egr2- and Fas-dependent manners, plays a criticalrole in suppressing humoral immunity. Here, FAS is linked to systemic lupus erythematosus.