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The microglial "activation" continuum: from innate to adaptive responses
Terrence Town1, Veljko Nikolic, Jun Tan
1Section of Immunobiology, Yale University School of Medicine, 300 Cedar St, New Haven, CT 06520-8011, USA. terrence.town@yale.edu
Journal of Neuroinflammation
|November 2, 2005
Summary
Reactive microglia exhibit a spectrum of activation states, from innate phagocytosis to adaptive antigen presentation, depending on the stimulus. This plasticity is crucial for understanding neuroinflammatory diseases like Alzheimer's.
Area of Science:
- Neuroimmunology
- Central Nervous System (CNS) Innate Immunity
Background:
- Microglia are myeloid-derived innate immune cells residing in the CNS.
- Traditionally viewed as macrophage-like, reactive microglia possess diverse CNS roles.
- Microglial activation is a continuum, not a single phenotype.
Purpose of the Study:
- To review the spectrum of microglial activation states.
- To explore stimulus-dependent microglial responses.
- To highlight the relevance of microglial plasticity in neuroinflammation.
Main Methods:
- Review of peripheral innate immune cell functions (macrophages, dendritic cells).
- Discussion of various microglial stimuli (PAMPs, myelin, beta-amyloid, CD40L, immunotherapy).
- Interpretation of stimulus-specific microglial responses.
Main Results:
- Microglial activation exists on a spectrum from innate (phagocytic) to adaptive (antigen-presenting) functions.
- The specific activation phenotype is dictated by the type of stimulation.
- Microglia display significant plasticity in response to diverse challenges.
Conclusions:
- Reactive microglia are highly plastic immune cells within the CNS.
- Understanding this plasticity is key for neurodegenerative and neuroinflammatory diseases.
- This includes conditions such as encephalitis, multiple sclerosis, and Alzheimer's disease.