γδ T cells and adipocyte IL-17RC control fat innervation and thermogenesis

The sympathetic nervous system innervates peripheral organs to regulate their function and maintain homeostasis, whereas target cells also produce neurotrophic factors to promote sympathetic innervation^1,2. The molecular basis of this bi-directional communication remains to be fully determined. Here we use thermogenic adipose tissue from mice as a model system to show that T cells, specifically γδ T cells, have a crucial role in promoting sympathetic innervation, at least in part by driving the expression of TGFβ1 in parenchymal cells via the IL-17 receptor C (IL-17RC). Ablation of IL-17RC specifically in adipose tissue reduces expression of TGFβ1 in adipocytes, impairs local sympathetic innervation and causes obesity and other metabolic phenotypes that are consistent with defective thermogenesis; innervation can be fully rescued by restoring TGFβ1 expression. Ablating γδ Τ cells and the IL-17RC signalling pathway also impairs sympathetic innervation in other tissues such as salivary glands. These findings demonstrate coordination between T cells and parenchymal cells to regulate sympathetic innervation.