PD-1 Inhibitory Receptor Downregulates Asparaginyl Endopeptidase and Maintains Foxp3 Transcription Factor Stability in Induced Regulatory T Cells.

CD4 T cell differentiation into multiple T helper (Th) cell lineages is critical for optimal adaptive immune responses. This report identifies an intrinsic mechanism by which programmed death-1 receptor (PD-1) signaling imparted regulatory phenotype to Foxp3 Th1 cells (denoted as TbetiTreg cells) and inducible regulatory T (iTreg) cells. TbetiTreg cells prevented inflammation in murine models of experimental colitis and experimental graft versus host disease (GvHD).