Human microglia cultures: a powerful model to study their origin and immunoreactive capacity

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Human microglia are crucial immune cells in the central nervous system.
• Establishing pure, long-term human microglia cultures is vital for studying their function.
• Previous research has focused on rodent microglia, necessitating human-derived models.

Purpose of the Study:

• To establish and characterize pure human microglia cultures from fetal brain.
• To investigate the morphology, marker expression, and functional capabilities of these cultured microglia.
• To analyze major histocompatibility complex (MHC) antigen expression and its modulation by gamma-interferon (IFN).

Main Methods:

• Long-term culture of human fetal astrocytes to induce microglial differentiation.
• Cell passage and analysis of morphology, microglial marker positivity, and growth rates.
• Assessment of major histocompatibility complex (MHC) class I and II antigen expression with and without gamma-interferon (IFN) stimulation.

Main Results:

• Pure human microglia cultures were successfully established and maintained for over 50 passages.
• Two distinct subpopulations, ameboid (reactive) and ramified (resting), were observed, with ramified cells increasing over time.
• Both subpopulations demonstrated phagocytosis and proliferation; MHC class II was upregulated by IFN in ameboid cells, while MHC class I was upregulated in both.
• Beta 2 microglobulin dissociation from HLA A-B-C molecules was noted in stimulated cells.

Conclusions:

• Long-term human microglia cultures provide a valuable model for studying microglial biology.
• Cultured human microglia exhibit distinct subpopulations and functional characteristics mirroring in vivo observations.
• Differential MHC antigen expression suggests distinct roles and responses of microglial subtypes to immune stimuli.