From Monocytes to M1/M2 Macrophages: Phenotypical vs. Functional Differentiation

Abstract

Studies on monocyte and macrophage biology and differentiation have revealed the pleiotropic activities of these cells. Macrophages are tissue sentinels that maintain tissue integrity by eliminating/repairing damaged cells and matrices. In this M2-like mode, they can also promote tumor growth. Conversely, M1-like macrophages are key effector cells for the elimination of pathogens, virally infected, and cancer cells. Macrophage differentiation from monocytes occurs in the tissue in concomitance with the acquisition of a functional phenotype that depends on microenvironmental signals, thereby accounting for the many and apparently opposed macrophage functions. Many questions arise. When monocytes differentiate into macrophages in a tissue (concomitantly adopting a specific functional program, M1 or M2), do they all die during the inflammatory reaction, or do some of them survive? Do those that survive become quiescent tissue macrophages, able to react as naïve cells to a new challenge? Or, do monocyte-derived tissue macrophages conserve a “memory” of their past inflammatory activation? This review will address some of these important questions under the general framework of the role of monocytes and macrophages in the initiation, development, resolution, and chronicization of inflammation.

Rabbit M1 and M2 macrophages can be induced by human recombinant GM‐CSF and M‐CSF

“…Little gene expression of IL‐1β was observed in M‐MΦ. The polarized macrophages phenotypes exhibited by rabbit macrophages were similar to that of human and mouse macrophages based on cytokine profiles and other parameters measured 22. In this study, we maintained having M‐CSF during the stimulation step (Fig.…”

Inhibition of RON kinase potentiates anti-CTLA-4 immunotherapy to shrink breast tumors and prevent metastatic outgrowth

“…41 RON activation has previously been reported to skew macrophages to the M2 phenotype and attenuate inflammation. 42 When we compared expression levels of differentially regulated genes in our study with previously published datasets corresponding to defined M1 versus M2 states, 43 we found that RON activation did not strictly correlate with either the M1 or M2 state ( Fig S2 ).…”

Immunomodulatory Effect of Imiquimod Through CCL22 Produced by Tumor-associated Macrophages in B16F10 Melanomas

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