Distinct regulation of MHC molecule expression on astrocytes and microglia during viral encephalomyelitis

Area of Science:

• Neuroimmunology
• Cellular Immunology
• Virology

Background:

• Viral infections trigger neuroinflammation involving glial cells and T cells.
• Major histocompatibility complex (MHC) molecules are crucial for immune cell communication.
• Understanding glial cell responses to viral encephalitis is vital for therapeutic strategies.

Purpose of the Study:

• To investigate the interplay between glial cells (astrocytes and microglia) and T cells during viral-induced central nervous system (CNS) inflammation.
• To compare the expression patterns of MHC class I and class II molecules on astrocytes and microglia in response to viral infection.

Main Methods:

• Utilized transgenic mice expressing green fluorescent protein in astrocytes.
• Infected mice with a neurotropic coronavirus.
• Employed flow cytometry for phenotypic characterization of astrocytes and microglia.
• Quantified MHC molecule expression and correlated it with interferon-gamma (IFN-γ) levels and lymphocyte infiltration.

Main Results:

• Astrocytes upregulated MHC class I expression with a delay compared to microglia.
• Microglia showed potent upregulation of MHC class II, while astrocytes had minimal expression.
• Maximal MHC expression in both cell types correlated with IFN-γ levels and lymphocyte presence.
• MHC molecule expression on glia remained elevated even after IFN-γ levels declined and the virus was cleared.

Conclusions:

• Astrocytes and microglia exhibit distinct regulation of MHC class I and class II expression during viral CNS inflammation.
• Sustained MHC expression on glial cells post-viral clearance indicates a potential for continued antigen presentation.
• These findings highlight the complex role of glial cells in the adaptive immune response within the CNS.