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Published on: June 23, 2013
Monitoring Macrophage Polarization in Infectious Disease, Lesson From SARS-CoV-2 Infection
Soraya Mezouar1,2, Jean-Louis Mege1,3
1Centre National de la Recherche Scientifique, Établissement Français du Sang, Anthropologie Bio-Culturelle, Droit, Éthique et Santé, Aix-Marseille University, Marseille, France.
Insights
Macrophage polarization is not a relevant indicator for COVID-19 patient monitoring. New functional subsets of myeloid cells offer better biomarkers for assessing COVID-19 complication risks.
Area of Science:
- Immunology
- Virology
- Pathology
Background:
- Macrophage polarization is a widely used concept to classify myeloid cell activation in human diseases.
- In COVID-19, studies have explored macrophage polarization for disease prognosis and monitoring.
- However, SARS-CoV-2 induces an in vitro activation state in monocytes and macrophages that doesn't fit traditional polarization categories.
Purpose of the Study:
- To critically re-evaluate the concept of macrophage polarization in the context of viral infections, specifically COVID-19.
- To explore alternative methods for assessing monocyte and macrophage activation in COVID-19 patients.
- To identify novel biomarkers for predicting COVID-19 complications.
Main Methods:
- Review of existing literature on macrophage polarization and COVID-19.
- Analysis of high-throughput data on monocyte and macrophage function in COVID-19 patients.
- Comparison of traditional polarization models with observed myeloid cell activation states.
Main Results:
- Monocytes and macrophages in COVID-19 patients are activated but do not exhibit classical polarization profiles.
- Traditional polarization categories are not relevant for assessing monocyte and macrophage activation in COVID-19.
- High-throughput analysis identified novel functional subsets of myeloid cells in COVID-19.
Conclusions:
- The concept of macrophage polarization is insufficient for characterizing myeloid cell activation in COVID-19.
- Newly identified functional myeloid cell subsets are superior biomarkers for assessing COVID-19 complication risk.
- Macrophage polarization may remain relevant for evaluating pharmacological interventions.
Abstract:
The concept of macrophage polarization has been largely used in human diseases to define a typology of activation of myeloid cells reminiscent of lymphocyte functional subsets. In COVID-19, several studies have investigated myeloid compartment dysregulation and macrophage polarization as an indicator of disease prognosis and monitoring. SARS-CoV-2 induces an in vitro activation state in monocytes and macrophages that does not match the polarization categories in most studies. In COVID-19 patients, monocytes and macrophages are activated but they do not show a polarization profile. Therefore, the investigation of polarization under basic conditions was not relevant to assess monocyte and macrophage activation. The analysis of monocytes and macrophages with high-throughput methods has allowed the identification of new functional subsets in the context of COVID-19. This approach proposes an innovative stratification of myeloid cell activation. These new functional subsets of myeloid cells would be better biomarkers to assess the risk of complications in COVID-19, reserving the concept of polarization for pharmacological programme evaluation. This review reappraises the polarization of monocytes and macrophages in viral infections, particularly in COVID-19.
