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MICROGLIAL BIOLOGY


MICROGLIAL BIOLOGY
Microglial cells are mesenchymal cells derived from yolk sac that come to reside in the CNS. They are a unique resident population with the capacity for self-renewal. Microglia provide constant surveillance of the local microenvironment, moving back and forth up to 1.5 µm/min. Microglial processes can grow and shrink up to 2-3 µm/min. They have a territory 15-30 µm wide, with little overlap with each other. Resting microglia have soma of 5-6 µm diameter, and activated microglia are ameboid in appearance, with soma of approximately 10 µm diameter.

MICROGLIAL BIOLOGY

Microglia can carry out phagocytosis of debris and apoptotic cells, remodel and remove synapses in developing and adult CNS, and respond to injury or pathogens. Microglia have receptors for multiple types of stimuli, such as ATP (indicator of local damage), toll-like receptors (TLRs) that respond to molecules released from dying cells (DAMPS: damage-associated molecular patterns) or pathogens (PAMPS: pathogen associated molecular patterns) such as LPS on gram-negative bacteria, or double-stranded RNA in viruses.
Reactive microglia produce reactive oxygen species (ROS), reactive nitrogen species (RNS, such as NO), proinflammatory cytokines (IL-1β, IL-6, TNF-α), matrix metalloproteinases (MMPs), and neurotrophic factors (such as NGF, TGF-β, neurotrophin 4/5, GDNF, FGF). Such signal molecules from activated microglia can affect neurons and astrocytes, inducing dysfunction.

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