Microglia



Microglia are a type of glial cell that act as the immune cells of the Central nervous system (CNS). Microglia, the smallest of the glial cells, can act as phagocytes, cleaning up CNS debris. Most serve as representatives of the immune system in the brain and spinal cord.

Microglia are close cousins of other phagocytic cells including macrophages and dendritic cells.

Microglia are thought to be highly mobile cells that play numerous important roles in protecting the nervous system.

Origin
Microglia are derived from myeloid progenitor cells (as are macrophages and dendritic cells) which come from the bone marrow. During embryonic development, however, they migrate to the CNS to differentiate into microglia.

Further development
After phagocytosis of lipid droplets and other debris (usually from tissue necrosis), microglia are termed gitter cells. A gitter cell is globular and swollen and can also be called a compound granule cell or compound granular corpuscle.

Clinical significance
Microglia are also thought to play a role in neurodegenerative disorders such as Alzheimer's disease, dementia, multiple sclerosis and Amyotrophic lateral sclerosis. They are responsible for producing an inflammatory reaction to brain trauma and are the main HIV-1 target cells in the central nervous system. .

History
Babes described activation of microglia in a rabies case in 1897, but did not know what the clusters of microglia he saw were (Streit et al., 2004). Franz Nissl and F. Robertson first described microglial cells, and Pio del Rio-Hortega, a student of Santiago Ramón y Cajal, first called the cells "microglia" around 1920. Cell staining techniques in the 1980s showed that microglia are related to macrophages.