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Immunohistochemical localization of macrophages and microglia in the adult and developing mouse brain
Abstract:
Macrophages and microglia in the developing and adult mouse brain have been identified by immunohistochemical localization of the macrophage-specific antigen F4/80 and monoclonal antibodies to the FcIgG1/2b (2.4G2) and type-three complement (Mac-1) receptors. In the adult mouse there are two classes of F4/80-positive cells; those associated with the choroid plexus, ventricles and leptomeninges and the microglia. The cells bearing Fc and complement receptors are indistinguishable, by their morphology and distribution, from those revealed by F4/80. During development macrophages invade the brain and can be followed through a series of transitional forms as they differentiate to become microglia. Macrophage invasion occurs when naturally dying cells are observed in large numbers and this is consistent with the idea that dying neurons and axons provide a stimulus for macrophage infiltration. Our results provide strong support for the hypothesis that the microglia are derived from monocytes and show that microglia possess receptors which would allow them to play a part in the immune defence of the nervous system.
Insights
Microglia in the mouse brain originate from blood monocytes. These cells, identified by F4/80 antigen and specific receptors, play a role in the nervous system's immune defense.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Macrophages and microglia are key immune cells in the brain.
- Identifying their origins and functions is crucial for understanding neuroinflammation and brain health.
Purpose of the Study:
- To investigate the origin and differentiation of microglia in the developing and adult mouse brain.
- To characterize the surface markers and receptors of microglia and their relationship to macrophages.
Main Methods:
- Immunohistochemical localization using F4/80 antigen and monoclonal antibodies (2.4G2, Mac-1).
- Morphological and distributional analysis of F4/80-positive cells and receptor-bearing cells.
- Tracking macrophage differentiation during brain development.
Main Results:
- Two classes of F4/80-positive cells identified: perivascular/meningeal and microglia.
- Cells with Fc and complement receptors are morphologically and distributionally similar to F4/80-positive cells.
- Macrophages invade the developing brain, differentiating into microglia, potentially stimulated by dying neurons/axons.
Conclusions:
- Strong evidence supports microglia derivation from blood monocytes.
- Microglia express receptors (Fc, Mac-1) enabling immune functions within the central nervous system.
- These findings highlight microglia's role in nervous system immune defense.