Systemic lupus erythematosus (SLE) is an autoimmune disease that is mainly caused by excessive accumulation of autoantibodies that target autoantibodies such as nucleic acids. T helper (Th) cell have been associated with the development of SLE. Typically, different subsets of Th cells secrete various cytokines to regulate the disease progression. IL-12 and IL-23 participate in the differentiation and activation of multiple Th cell subsets, including Th1, Th2, Th9, Th17, regulatory T (Treg) and follicular helper T (Tfh) cells. Because of the signature p40 subunit shared by IL-12 and IL-23, blocking IL-12/IL-23 signaling may interfere the differentiation of Th cell and directly inhibit the secretion of proinflammatory cytokines. In this study, we examined the effects of anti−IL-12/23 p40 antibody on chronic graft-versus-host disease with lupus nephritis, and found that the therapeutic effectiveness was mediated through the inhibition of Tfh cell in mice. Moreover, anti−IL-12/23 p40 antibody inhibited human Tfh cell differentiation in vitro. These results strongly suggest that Tfh cell contribute to the pathogenesis of SLE, and the neutralization of IL-12/IL-23 signaling during Tfh cell differentiation may be critical for the treatment of SLE.