Phagocytes are cells present in the blood and other tissues capable of capturing animals microorganisms and cellular debris (in general, such particles are useless or harmful to the body) into the interior to eliminate, in a process known as phagocytosis . Its name comes from the Greek phagein, and I quote, suffix used with the meaning of 'cell', from the end kutos. There are many types of cells capable of performing phagocytosis, the cells of the immune system that do are of vital importance in defending the body against infections . are present in all animals and are highly developed in vertebrates . One liter of blood human contains about six billion of these cells. were discovered in 1882 in larvae of starfish and Ilya Ilyich Mechnikov . Because of this work, Metchnikoff was awarded the Nobel Prize in Physiology or Medicine in 1908. are also present in animal species, in fact, some amoebae have a behavior similar to macrophages (a type of phagocytes), suggesting that appeared in an early stage the evolution .

Micrograph obtained by scanning electron microscopy of a neutrophil engulfing a producer of the anthrax bacteria, Bacillus anthracis (orange). Bacillary shows the half-digested in the phagocyte to the left (in yellow).In its generic sense, is often called 'phagocytes' cells in the immune system with phagocytic capacity (such as macrophages ). More precisely, not all phagocytes are white blood cells or immune cells: in humans and other animals are classified as "professional" and "unprofessional", depending on its effectiveness and whether you have functions other than phagocytosis. The professional phagocytes include the neutrophils , monocytes , macrophages, dendritic cells and mast cells , non-professional phagocytes include numerous elements in the human body and other leukocytes, such as epithelial cells , endothelial , fibroblasts and cells of the mesenchyme . The fundamental difference between the two types is that the professionals have cellular receptors on their surface that are able to distinguish between own and other substances the body. This specificity is the basis of recognition of the self against the alien and sustains defense against infection mediated by the immune system and healthy tissue remodeling (removing dead skin cells or nonfunctional).

During infection, professional phagocytes are attracted to the area invaded by pathogens by chemical signals from other bacteria or phagocytes that are present earlier. The attraction, called chemotaxis , is due to cellular receptors on the surface of certain substances bind phagocyte pathogens, allowing them to recognize and phagocytes. Some phagocytes destroy pathogens by reactive oxygen species and oxide Nitric . After phagocytosis, macrophages and dendritic cells are able to participate in antigen presentation (the manipulation of particles that have phagocytosed to expose its surface to other cells of the immune system recognize and are activated). These parts are "presented" to other immune cells, some of these macrophages and dendritic cells travel to a lymph node to make the presentation to a large number of cells. This process is vital to generate immunity. However, some pathogens have developed strategies to evade this response.

History

The Russian zoologist Ilya Ilyich Mechnikov (1845-1916) first described the specialized cells that were involved in the defense against microbial infections. In 1882, he studied cell motile (free movement) in the larvae of starfish with the suspicion that involved in cellular immunity. To test their hypothesis, Mandarin spines inserted the larvae. After several hours, observed that motile cells were surrounded by the fence. Mechnikov traveled to Vienna and shared their findings with Carl Friedrich Claus , who suggested the name "phagocyte" for these cells.

A year later, Mechnikov studied a crustacean known freshwater Daphnia , a tiny transparent animal could be examined directly under a microscope. Found that spores fungus attacking the animal was destroyed by phagocytes. He continued his observations with leukocytes of mammals and found that the bacteria Bacillus anthracis could be absorbed and destroyed by these cells in a process dubbed "phagocytosis." suggested that phagocytes and were used for defense against invading organisms.

In 1903, Almroth Wright discovered that phagocytosis was enhanced by antibodies specific named opsonins , the Greek opson, seasoning. Mechnikov was honored along with Paul Ehrlich the Nobel Prize in Physiology or Medicine in 1908 for his work on phagocytes and phagocytosis.

Although the significance of these findings was accepted in early twentieth century, the complicated relationships between phagocytes and other immune system components would not be known until the decade of 1980.


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