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Updated: Apr 19, 2026
Analysis of Microglia and Monocyte-derived Macrophages from the Central Nervous System by Flow Cytometry
Published on: June 22, 2017
Resident microglia, and not peripheral macrophages, are the main source of brain tumor mononuclear cells
Annett Müller1, Susan Brandenburg1, Kati Turkowski1
1Department of Neurosurgery, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Abstract:
Gliomas consist of multiple cell types, including an abundant number of microglia and macrophages, whereby their impact on tumor progression is controversially discussed. To understand their unique functions and consequently manipulate either microglia or macrophages in therapeutic approaches, it is essential to discriminate between both cell populations. Because of the lack of specific markers, generally total body irradiated chimeras with labeled bone marrow cells were used to identify infiltrated cells within the brain. However, total body irradiation (TBI) affects the blood-brain barrier integrity, which in turn potentially facilitates immune cell infiltration. In this study, changes on the blood-brain barrier were avoided using head-protected irradiation (HPI). Head protection and total body irradiated chimeras exhibited similar reconstitution levels of the myeloid cell lineage in the blood, enabling the comparable analyses of brain infiltrates. We demonstrate that the HPI model impeded a massive unspecific influx of donor-derived myeloid cells into naive as well as tumor-bearing brains. Moreover, experimental artifacts such as an enlarged distribution of infiltrated cells and fourfold increased tumor volumes are prevented in head-protected chimeras. In addition, our data evidenced for the first time that microglia are able to up-regulate CD45 and represent an inherent part of the CD45(high) population in the tumor context. All in all, HPI allowed for the unequivocal distinction between microglia and macrophages without alterations of tumor biology and consequently permits a detailed and realistic description of the myeloid cell composition in gliomas.
Insights
Head-protected irradiation (HPI) enables distinguishing microglia from macrophages in gliomas. This method prevents experimental artifacts, allowing realistic analysis of myeloid cell composition in brain tumors.
Area of Science:
- Neuro-oncology
- Immunology
- Cell Biology
Background:
- Gliomas contain diverse myeloid cells, including microglia and macrophages, with debated roles in tumor progression.
- Distinguishing these cell types is crucial for therapeutic strategies, but lacks specific markers.
- Previous methods using total body irradiation (TBI) can alter blood-brain barrier integrity, confounding immune cell infiltration studies.
Purpose of the Study:
- To develop a method for reliably differentiating microglia and macrophages in gliomas.
- To investigate the impact of irradiation methods on blood-brain barrier integrity and immune cell infiltration.
- To accurately characterize myeloid cell populations within the glioma microenvironment.
Main Methods:
- Utilizing head-protected irradiation (HPI) in chimeric mouse models to maintain blood-brain barrier integrity.
- Comparing HPI with total body irradiation (TBI) in terms of myeloid cell reconstitution and brain infiltration.
- Analyzing brain infiltrates in naive and tumor-bearing brains using labeled bone marrow cells.
Main Results:
- HPI effectively prevented non-specific myeloid cell influx into the brain, unlike TBI.
- Head-protected chimeras showed no experimental artifacts like enlarged cell distribution or increased tumor volume.
- Microglia were identified as capable of up-regulating CD45, contributing to the CD45(high) population in gliomas.
- The HPI model allowed clear distinction between microglia and macrophages without altering tumor biology.
Conclusions:
- Head-protected irradiation is a superior method for studying myeloid cell populations in gliomas.
- This technique facilitates accurate discrimination between microglia and macrophages, crucial for understanding their distinct roles.
- The findings enable a more precise characterization of the myeloid cell composition in gliomas, paving the way for targeted therapies.
