The nervous system and innate immunity: the neuropeptide connection

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Abstract
Notch receptors are processed by γ-secretase acting in synergy with T cell receptor signaling to sustain peripheral T cell activation. Activated CD4+ T cells differentiate into T helper type 1 (TH1) or TH2 subsets. Molecular cues directing TH1 differentiation include expression of the TH1-specific transcription factor T-bet, encoded by Tbx21. However, the regulation of Tbx21 remains incompletely defined. Here we report that Notch1 can directly regulate Tbx21 through complexes formed on the Tbx21 promoter. In vitro, γ-secretase inhibitors extinguished expression of Notch, interferon-γ and Tbx21 in TH1-polarized CD4+ cells, whereas ectopic expression of activated Notch1 restored Tbx21 transcription. In vivo, administration of γ-secretase inhibitors substantially impeded TH1-mediated disease progression in the mouse experimental autoimmune encephalomyelitis model of multiple sclerosis. Thus, using γ-secretase inhibitors to modulate Notch signaling may prove beneficial in treating TH1-mediated autoimmunity.