Baicalin ameliorates lupus autoimmunity by inhibiting differentiation of Tfh cells and inducing expansion of Tfr cells

Baicalin is a natural compound isolated from Chinese herb, which has been reported as an anti-inflammatory drug. Here, we demonstrated that Baicalin treatment could reduce urine protein, inhibit anti-ds-DNA antibody titers, and ameliorate lupus nephritis in MRL/lpr lupus-prone mice. Baicalin inhibited Tfh cell differentiation and IL-21 production, but promoted Foxp3(+) regulatory T cell differentiation including part of follicular regulatory T (Tfr) cells. Intravenous injection of Baicalin-induced Foxp3(+) regulatory T cells could relieve nephritis, inhibit Tfh cell differentiation and IL-21 production. Baicalin inhibited mTOR activation, reduced mTOR agonist-mediated Tfh cell expansion and increased Tfr cells. These data suggest that Baicalin attenuates lupus autoimmunity by up- and downregulating the differentiation of Tfr cells and Tfh cells, respectively. Baicalin and ex vivo expanded Foxp3(+) regulatory T cells are promising therapeutics for the treatment of lupus.