Phosphotyrosine antibodies specifically label ameboid microglia in vitro and ramified microglia in vivo

Area of Science:

• Neuroscience
• Cell Biology
• Immunology

Background:

• Previous studies identified phosphotyrosine immunoreactivity in GFAP-negative neuroglia in adult rat brain and retina.
• The specific cell type responsible for this immunoreactivity remained unidentified.

Purpose of the Study:

• To identify the specific cell type exhibiting phosphotyrosine immunoreactivity in the adult rat brain.
• To investigate the role and significance of phosphotyrosine-containing proteins in microglia.

Main Methods:

• Immunohistochemistry using a phosphotyrosine-specific antibody.
• Morphological and ultrastructural analysis of immunoreactive cells.
• Co-localization studies with Bandeiraea simplifolia-1 lectin (B4 isolectin), a microglial marker.
• Analysis of primary neonatal rat brain microglial cultures.

Main Results:

• Phosphotyrosine-immunoreactive cells in the adult brain exhibit morphological and ultrastructural characteristics of microglia.
• Phosphotyrosine co-localizes with the microglial-specific B4 isolectin.
• Amoeboid microglia in vitro stain positive for phosphotyrosine, and microglia are the sole phosphotyrosine-immunoreactive cells after 7 days in culture.
• The in vitro staining pattern mirrors the developmental expression of phosphotyrosine in vivo, with microglia being the only stained elements in mature brain.

Conclusions:

• The study definitively identifies microglia as the cell type expressing phosphotyrosine in the mature rat brain.
• Phosphotyrosine expression in microglia appears to be developmentally regulated and specific to this cell type in the adult brain.
• The findings suggest a potentially significant, microglial-specific role for phosphotyrosine-containing proteins in neural function.