Regulatory T cells restrain skin inflammation by modulating peripheral neuron activation.

The skin integrates diverse signals discerned by sensory neurons and immune cells to elicit adaptive responses to a range of stresses. Considering interactions between nervous and immune systems, we questioned whether regulatory T cells (Treg cells), a T cell subset that suppresses systemic and local inflammation, can modulate activation of peripheral neurons. Short-term ablation of Treg cells increased neuronal activation to noxious stimuli independently from immunosuppressive function. We find that a population of skin Treg cells is highly enriched for Penk expression, a precursor for endogenous opioid enkephalins. Acute depletion of Penk-expressing Treg cells, or cell-specific ablation of Penk in Treg cells increases neuronal activation in response to noxious stimuli and associated inflammation. Our study indicates that a population of Treg cells exhibits neuromodulatory activity to restrain inflammation.