The human immune system is made up of many different structures and processes. Organs such as bone marrow, con, spleen or lymph nodes are involved in this function, which is essential for the production of immune cells.
In this article we will describe functions and diseases related to microglia, One of these cells.
What is microglia
Microglia is a type of glial cell found in the central nervous system. The term is used to refer to a collection of cells that perform similar functions, mainly related to immune defense and phagocytosis of potentially harmful elements for neurons.
The term “microglia” was coined in 1920 by Pius de Río Hortega, a disciple of neuroscience pioneer Santiago Ramón y Cajal. The immune functions of these cells have been known since their discovery, although knowledge of their characteristics has increased in recent decades.
It is a very versatile type of glia: the structure of the microglia varies depending on the functions performed by each cell, Where it is located and the chemical signals it receives from adjacent neurons. We speak of “phenotype” to designate the specific form that each microglia takes.
They come from progenitor cells of the same lineage as those that make up the blood, probably located in the bone marrow or the yolk sac attached to the embryo. Some of these cells migrate to the brain during intrauterine development; once they reach this structure, they differentiate into microglia.
Glial cells or glia are located in the nervous systemThat is, in the brain, spinal cord, and cranial and spinal nerves. They support neurons in different ways: they support them physically, they nourish and eliminate pathogens, damaged tissue and waste, they promote the transmission of neural impulses through the formation of myelin …
Among the types of cells classified as glia are astrocytes, which are essential for the structure and function of the blood-brain barrier, oligodendrocytes, which create the myelin sheaths of the central nervous system, and Schwann cells. , who do. the suburbs.
Functions of these cells
Microglia are mainly known for their immune and hygienic roles; however, it also performs various other functions, such as maintaining the balance of the extracellular environment of the nervous system or repairing damaged tissue.
1. Phagocytosis (waste disposal)
These cells phagocytize (“eat”) different types of central nervous system compounds: injured and dead cells, waste, viruses, bacteria, neurofibrillary tangles, Neuretic plaques … After phagocytosis, the microglia and its target remain inactive, thus reducing the risk of impaired functioning of the nervous system.
2. Maintenance of homeostasis
Microglia send signals via cytokines to other types of cells, such as neurons, astrocytes, and T cells, which are also involved in the immune system. Among the consequences of this function are the regulation of homeostasis of the extracellular environment, as well as the promotion of inflammation.
3. Inflammation and repair of damage
When tissue in the central nervous system is damaged or infectedThe microglia facilitates inflammation in this way the process of repairing the damaged cells begins, during which these cells are very important.
In addition, in the event of a spinal cord injury, the microglia removes the affected neural branches, thus allowing the creation of new nerve connections.
4. Presentation of antigens
By inflaming tissue, T cells cross the blood-brain barrier and enter the central nervous system. Once here they join microglia cells that have phagocytosed antigens (Particles from which antibodies are produced); this improves threat elimination and injury recovery.
5. Cell destruction (cytotoxicity)
Microglia have the ability to destroy bacteria, viruses, infected neurons, and other types of cells by releasing hydrogen peroxide and nitric oxide. This response is sometimes too aggressive and damages significant amounts of healthy tissue, causing even greater brain damage.
Diseases related to microglia
Dysfunctions of the microglia are associated with very diverse alterations. These cells appear to be significantly involved in neurodegenerative diseases such as Alzheimer’s diseaseWhere neuritic plaques and neurofibrillary tangles accumulate in the brain: cytotoxicity of microglia attacks healthy neurons adjacent to damaged tissue.
Microglial cells play a similar role in the development of dementia due to infection with HIV, the AIDS virus. In fact, this disease also directly affects microglia, infecting and promoting neurotoxicity. Microglia is also implicated in other infectious diseases, such as herpetic encephalitis and bacterial meningitis.
Research reveals that glia it is important in the onset of neuropathic pain, Which manifests as disorders such as allodynia or phantom limb syndrome. This is because they are activated in response to nerve damage and promote the chronic release of chemical compounds associated with the sensation of pain.