The defective generation or function of regulatory T (Treg) cells in autoimmune disease contributes to chronic inflammation and tissue injury. We report the identification of FoxA1 as a transcription factor in T cells that confers suppressive properties in a newly identified Treg cell population, herein called FoxA1+ Treg cells. FoxA1 bound to the Pdl1 promoter, inducing programmed cell death ligand 1 (Pd-l1) expression, which was essential for the FoxA1+ Treg cells to kill activated T cells. FoxA1+ Treg cells develop primarily in the central nervous system in response to autoimmune inflammation, have a distinct transcriptional profile and are
CD4+FoxA1,+
CD47,+
CD69,+PD-L1hig,
FoxP3-. Adoptive transfer of stable FoxA1+ Treg cells inhibited experimental autoimmune encephalomyelitis in a FoxA1-and Pd-l1-dependent manner. The development of FoxA1+ Tregcells is induced by interferon-β (IFN-β) and requires T cell-intrinsic IFN-α/β receptor (Ifnar) signaling, as the frequency of FoxA1+ Treg cells was reduced in Ifnb-/- and Ifnar-/- mice. In individuals with relapsing-remitting multiple sclerosis, clinical response to treatment with IFN-β was associated with an increased frequency of suppressive FoxA1+ Treg cells in the blood. These findings suggest that FoxA1 is a lineage-specification factor that is induced by IFN-β and supports the differentiation and suppressive function of FoxA1+ Treg cells.