Table 2.

Adipose tissue macrophage phenotypic classifications in humans.

Type	Cell surface expression profile	Secretion profile	Function
M1-like “classically activated”	CD14+CD16++ CD11c+CD31+CD44+CD45+CD206−HLA-DR+	TNF-α, IL-6, IL-8, IL-1β, NO	Pro-inflammatory, pro-oxidative, antimicrobial, pathogen clearance
Intermediate population	CD14+CD16+ CD11c+CD45+CD206+	TNF-α, IL-6, IL-8	Pro-inflammatory and pro-oxidative, tissue remodelling
M2-like “alternatively activated”	CD14++ CD16+ CD45+CD163+CD206+	IL-10, TGF-β	Anti-inflammatory, fibrosis, tissue surveillance, angiogenesis

Text in italics and quotes emphasises other common terms to describe these cells. Intermediate population refers to adipose tissue macrophages expressing M2-like surface markers (e.g., CD206), while demonstrating an M1-like pro-inflammatory function. Expression pattern of CD14 and CD16 is best established on monocytes rather than macrophages. It is important to note that macrophage populations within adipose tissue can express markers of alternatively activated cells (e.g., CD206+) while also imparting a pro-inflammatory, classically activated function within the tissue, highlighting the spectrum of macrophage polarity within adipose tissue.

CD, cluster of differentiation; HLA-DR, human leukocyte antigen-antigen D related; IL, interleukin; NO, nitric oxide; TGF-β, transforming growth factor-beta; TNF-α, tumour necrosis factor-α.