Deficiency in T follicular regulatory cells promotes autoimmunity.

T follicular regulatory (Tfr) cells are a new subset of regulatory T (T reg) cells localized in the germinal center to limit the humoral response. Until now, the physiological function of Tfr cells has been largely unknown. In this study, we developed a Bcl6fl/flFoxp3Cre mouse to analyze the function of Tfr cells in immune and autoimmune responses. These mice exhibited enhanced immunity to influenza virus; moreover, Bcl6fl/flFoxp3Cre/Cre mice developed late-onset spontaneous autoimmune diseases, affecting the salivary glands with lymphocyte infiltration and antibody deposition. In a mouse experimental Sjögren's syndrome model, ablation of Bcl6 in T reg cells greatly enhanced disease development. Conversely, Bcl6fl/flCd4Cre mice were protected in the model. Thus, our study indicates that Tfr cells control autoimmune diseases and can be targeted in infectious and autoimmune disease.