Figure 1.

ILCs in the adipose tissue. ILC1s and ILC2s regulate the balance between M1 and M2 macrophages in the adipose tissue. External stimuli such as high-fat diet (HFD) or cold exposure modulate the activity of the ILC which impacts the M1/M2 ratio in the tissue. ILC1 promotes M1 macrophage polarization through the production of TNF-α and IFN-γ, which increases not only lipid storage but also inflammation and adipose fibrosis. ILC2s are activated by IL-33 and regulated by the sympathetic nervous system (SNS) in response to cold exposure. Consequently, IL-5 and IL-13 production by ILC2s is enhanced, which promotes eosinophil recruitment and M2 macrophage polarization, respectively. This type 2 response promotes the beiging of adipose tissues and thermogenesis.