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Updated: Apr 5, 2026
Macrophage Differentiation and Polarization into an M2-Like Phenotype using a Human Monocyte-Like THP-1 Leukemia Cell Line
Published on: August 2, 2021
CD73 Activity is Dispensable for the Polarization of M2 Macrophages
Dominik Eichin1, Juha P Laurila1, Sirpa Jalkanen1
1Medicity Research Laboratory, University of Turku, Turku, Finland.
Abstract:
The ectoenzyme CD73 catalyzes the hydrolysis of AMP, and is one of the most important producers of extracellular adenosine. On regulatory T cells, CD73 is necessary for immunosuppressive functions, and on Th17 cells CD73-generated adenosine exerts anti-inflammatory effects. However, the expression and function of CD73 in pro-inflammatory M1 and in immunosuppressive M2 macrophages is largely unknown. Here we show that CD73 expression and enzyme activity were induced in in vitro polarized pro-inflammatory human M(LPS+TNF) monocytes/macrophages, while CD73 was absent from immunosuppressive M(IL-4+M-CSF)-polarized macrophages. Inhibition of CD73 activity with the inhibitor AMPCP did not affect the polarization of human monocytes. In mice, CD73 was present on resident peritoneal macrophages. In striking contrast, elicited peritoneal macrophages remained CD73 negative regardless of their polarization towards either a pro-inflammatory M(LPS) or anti-inflammatory M(IL-4c) direction. Finally, the ability of peritoneal macrophages to polarize to pro- and anti-inflammatory cells was perfectly normal in CD73-deficient mice in vivo. These data indicate that, in contrast to other major leukocyte subpopulations, CD73 activity on macrophages does not play a major role in their polarization and that in mice host CD73 on any cell type is not required in vivo for peritoneal macrophage polarization towards either a pro- or an anti-inflammatory direction.
Insights
CD73 expression is induced in pro-inflammatory macrophages but absent in immunosuppressive ones. Macrophage polarization occurs normally in CD73-deficient mice, indicating CD73 is not essential for this process.
Area of Science:
- Immunology
- Cell Biology
- Enzymology
Background:
- CD73 is an ectoenzyme crucial for extracellular adenosine production.
- CD73 plays roles in T cell regulation, mediating immunosuppression and anti-inflammatory effects.
- The role of CD73 in macrophage polarization remains largely unexplored.
Purpose of the Study:
- To investigate the expression and function of CD73 in pro-inflammatory (M1) and immunosuppressive (M2) macrophages.
- To determine if CD73 activity influences macrophage polarization in vitro and in vivo.
- To assess the necessity of CD73 for peritoneal macrophage polarization in mice.
Main Methods:
- In vitro polarization of human monocytes into M1 and M2 macrophages.
- Assessment of CD73 expression and activity using specific stimuli and inhibitors (AMPCP).
- Analysis of CD73 expression in resident and elicited mouse peritoneal macrophages.
- Phenotypic analysis of peritoneal macrophages from CD73-deficient mice.
Main Results:
- CD73 expression and activity were induced in M(LPS+TNF)-polarized human macrophages but absent in M(IL-4+M-CSF)-polarized macrophages.
- CD73 inhibition did not alter human monocyte polarization.
- Resident mouse peritoneal macrophages expressed CD73, while elicited macrophages did not, irrespective of polarization.
- Peritoneal macrophage polarization in vivo was unaffected in CD73-deficient mice.
Conclusions:
- Macrophage CD73 activity is differentially regulated based on polarization state.
- CD73 is not essential for the in vitro or in vivo polarization of macrophages.
- Host CD73 expression is not required for peritoneal macrophage polarization in mice.
