Table 1.
Characteristics of M1, M2 and TAM. Different macrophage phenotypes share different characteristics in terms of polarising signals, membrane receptors, cytokines and chemokines released and function. The most commonly used markers for each macrophage type is given.
| M1-classically activated macrophages | M2-alternatively activated macrophages | TAM-tumour-associated macrophages | References | |
|---|---|---|---|---|
| Polarising signals | IFN-γ, LPS or TNF-a | IL-4, IL-13 (M2a), IC+TLR/IL-1R Ligands (M2b), IL-10 (M2c) | CSF-1, VEGF, CCL2/3/4/5/8, IL-4, IL-13, IL-10, TGF-β, PGE2 | [4], [9], [10] |
| Membrane receptors | TLR2, TLR4, CD16, CD32, CD64, CD80, CD86 | Scavenge receptor A/B, CD 14, CD 23, CD 163, MR | CD11b, CD45, F4/80 (mice), CXCR4, Gr1,CD68, VEGFR | [4], [9], [10] |
| Cytokines released | High IL-12, IL-23, low IL-10, IL-1, TNF, IL-6, ROI, RNI | High IL-10, low IL-12; TGF-β (M2c); low IL-1, TNF, IL-6 (not M2b); high decoy IL-1RII, IL-1R-antagonist, EGF, FGF, VEGF, TNF-β | FGF, PDGF, EGFR, VEGF, ANG1/2, IL-1/8, TNF-α, TP, MMP-2/9, CSF-1 | [4], [9], [10] |
| Chemokines released | CXCL 8/9/10/11/16 CCL2/3/4/5 | CCL 1/16/17/18/22/24 | CCL-2/3 | [4], [9], [10] |
| Function | Th2 responses, type II inflammation, allergy, killing and encapsulation of parasites | Th2 activation, immunoregulation, matrix deposition and tissue remodelling | Angiogenesis, tumour growth, tumour invasion, intravasation, immunosuppression, metastasis | [4], [9], [10] |
| Markers (mouse) | iNOS, CD197 | Arginase-1, CD163 | F4/80 | [4], [9], [10] |
Abbreviations are: IFN, interferon; LPS, lipopolysaccharide; TNF, tumour necrosis factor; IL, interleukin; IC, immune complexes; TLR, toll-like receptor; CSF, colony stimulating factor; VEGF, vascular endothelial growth factor; VEGFR, vascular endothelial growth factor receptor; CCL, CC chemokine ligand; TGF, transforming growth factor; PGE, prostaglandin E; ROI, reactive oxygen intermediates; RNI, reactive nitrogen intermediates; EGF, epidermal growth factor; FGF, fibroblast growth factor; PDGF, platelet-derived growth factor; EGFR, epidermal growth factor receptor; ANG, angiopoietin; MMP, matrix metalloproteinase; CXCL, chemokine (C-X-C motif) ligand.