Diffuse microglial proliferation after global ischemia in a patient with aplastic bone marrow

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• The origin of brain macrophages, particularly microglia, is debated.
• Some animal studies suggest circulating monocytes are the primary source of brain macrophages following injury.

Observation:

• In a 34-year-old male patient who experienced cardiac arrest, abundant microglia-like cells were observed in the brain.
• This patient's bone marrow showed near-total depletion of white-blood-cell precursors.

Findings:

• The presence of numerous microglia-like cells suggests a potential source within the brain itself.
• These cells exhibited characteristics of microglia and phagocytic activity.

Implications:

• Adult human brains may possess native microglial precursors capable of phagocytosis.
• This challenges the prevailing theory that brain macrophages exclusively derive from circulating monocytes.
• Findings suggest resident brain cells play a crucial role in neuroinflammation and repair.