Multiple types of immune cells are found in adipose tissues. In Immunity, Boulenouar et al. characterize type 1 innate lymphoid cells (ILCs) that reside in adipose tissues in both lean people and obese people. Adipose-tissue ILCs are a heterogeneous population that dynamically changes in response to high-fat diets and includes cytotoxic natural killer cells. Adipose tissue ILCs are phenotypically different from similar populations in spleen and liver. Curiously, in lean people, adipose-tissue ILCs can kill tissue-resident M2-polarized macrophages, which express the stress ligand RaeI recognized by natural killer cells. Adipose-tissue ILCs from obese people have diminished cytolytic activity; however, adoptive transfer of ILCs from lean donors enhances glucose intolerance in obese recipients. These findings suggest that ILCs contribute to the homeostasis of adipose-tissue macrophages, although fuller understanding of their interactions will require further study.

Immunity 46, 273–286 (2017)