Macrophage

Vital cycle

The macrophages are differentiated starting from the Monocyte S, which are blood phagocytes, themselves derived from the osseous Moelle. When a monocyte infiltrates fabrics while crossing the vascular Endothélium, it undergoes its final differentiation to become a macrophage. Monocytes, then the macrophages are attract towards the place of a Inflammation by Chimiotactisme. The signals of call are constitute various stimuli, derived from damaged cells (by Nécrose or Apoptose), from pathogenic, and products liberalized by the cells present at the site: the Histamine salted out by the Mastocyte S and the granulocytes basophilic, and of the Chimiokine S and Cytokine S released by macrophages.

Contrary to the neutrophiles, which are the cells phagocytic which are present most quickly instead of the ignition and which live only a few days, the lifespan of a macrophage goes several months at years. As they are completely differentiated cells, they do not divide.

Function

Phagocytosis

One of the main roles of the macrophages is the necrotic cleaning of Corps S and Corps apoptotic S, remains and dust in the case of the lungs. The elimination of the dead cells is important within the framework of the early phases of the chronic ignition. This elimination is dominated by the action of the granulocytes neutrophiles, which will be themselves phagocytes by the once aged macrophages (see CD31 for more details).

The elimination of dust and fabrics necrotic is dealt with more large scales (except ignition), by macrophages resident which remain at strategic places like the lungs, the liver, nervous fabrics, the bones, spleen and the fabrics conjunctive, and which digest the foreign particles like dust and the remains, but also the pathogenic ones, recruiting circulating macrophages where necessary.

When a macrophage introduces pathogenic, the formed intracellular blister is named Phagosome. It will amalgamate with a Lysosome. The radical free Enzymes lysosomiales and of the Oxygène (in particular hypochlorite) will kill and digest the intruder. However, certain organizations can resist this process and survive in the macrophage, like Mycobacterium tuberculosis or the Leishmania. A macrophage can digest a hundred bacteria before succumbing itself to its own enzymes of digestion.

Role in adaptive immunity

After having digested pathogenic, a macrophage can behave in APC, i.e. to present a Antigène so as to stimulate a specific Lymphocyte T. Lymphocytary stimulation by a macrophage is less than that induced by a dendritic Cellule, but the macrophages are able to present antigens associated with the molecules of the major Complexe with histocompatibility of class two, and thus to stimulate lymphocytes CD4 +.

An immunization also results in the production of Anticorps directed against the immunizing antigens. These antibodies will bind to the antigens of surface of the pathogenic ones. Some Isotypes are opsonisants, i.e. there exists on the phagocytes of the specific receivers of the constant fragments of the heavy chains of the antibodies. (In the case of IgG, they are the CD16, CD32 and CD64.) The macrophages have this type of receivers and the connection of a complex immune has these receivers starts phagocytosis. Thus, pathogenic which will be invisible with the eyes of a macrophage will become to it opsonized once.

Implication in human pathology

The macrophages take part in certain pathological phenomena, in particular:

the macrophages are able to store the abnormal lipids. Once " pleins" , they are the raw material of the plate of Athérosclérose. They bear then the name of spumous cells
the macrophages carry the molecules CD4 and CCR5, which returns them infectables by the stocks macrotropes of HIV. In practice, the infection with the HIV at the time of a sexual contamination passes by the macrophages.
the formation of the inflammatory Granulome depends on the macrophages.

Summon disorders, mostly off rare, ineffective phagocytosis and macrophage function cuts been described.

Macrophages prevalent are the concealments involved in creating the progressive plate lesions off Atherosclerosis.

When fighting Influenza, macrophages are dispatched to the throat. However, until the killer T concealments for the flu virus are found, the macrophages C more ramming than help. They not only destroy throat concealments infected with the flu virus drank also destroy several surrounding non-infected concealments.

Macrophages also play has role in Human Immunodeficiency Virus (HIV) infection. Like T concealments, macrophages edge Be infected with HIV, and even become has tank off ongoing virus replication throughout the body.

Macrophages changeable are concealments that play many roles. Ace scavengers, they rid the body off worn-out concealments and other remains. Foremost among the concealments that " present" crucial role in initiating the immune response. Ace secretory concealments, monocytes and macrophages vital are to the regulation off immune responses and the development off ignition; they churn out year amazing array off powerful chemical substances (monokines) including enzymes, complement proteins, and regulatory factors such ace interleukin-1. At the same time, they curry receptors for lymphokines that allow them to Be " activated" into individual-minded pursuit off microbes and tumor concealments-->

Macrophages resident

It already was mentions that the majority of the macrophages (in not-inflammatory situation) resident at strategic places. They are thus present at the most suitable places for microbial invasion or accumulation of remains of all kinds. It east gives different names to the macrophages according to their localizations. For example:

Histiocyte S in conjunctive fabrics
Cell of Kupffer in the liver
Cell microgliale in nervous fabrics
Osteoclast S in bone tissues

External bonds

off has book one the role macrophages in HIV pathogenesis
the review of poetry Macrophage

See too

Random links:

Paradox of Saint-Pétersbourg | Hippolyte Paul Jayr | Clèdes | Arthur Capell | Ephel Dúath