Brown adipose tissue harbors a distinct sub-population of regulatory T cells

Regulatory T (T _reg) cells are critical determinants of both immune responses and metabolic control. Here we show that systemic ablation of T_reg cells compromised the adaptation of whole-body energy expenditure to cold exposure, correlating with impairment in thermogenic marker gene expression and massive invasion of pro-inflammatory macrophages in brown adipose tissue (BAT). Indeed, BAT harbored a unique sub-set of T_reg cells characterized by a unique gene signature. As these T_reg cells respond to BAT activation upon cold exposure, this study defines a BAT-specific T_reg sub-set with direct implications for the regulation of energy homeostasis in response to environmental stress.