phagocytosis

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phagocytosis:

see endocytosisendocytosis
, in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm surges forward to meet and surround the material and a depression forms within the cell wall.
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Phagocytosis

A mechanism by which single cells of the animal kingdom, such as smaller protozoa, engulf and carry particles into the cytoplasm. It differs from endocytosis primarily in the size of the particle rather than in the mechanism; as particles approach the dimensions and solubility of macromolecules, cells take them up by the process of endocytosis.

Cells such as the free-living amebas or the wandering cells of the metazoa often can “sense” the direction of a potential food source and move toward it (chemotaxis). If, when the cell contacts the particle, the particle has the appropriate chemical composition, or surface charge, it adheres to the cell. The cell responds by forming a hollow, conelike cytoplasmic process around the particle, eventually surrounding it completely. Although the particle is internalized by this sequence of events, it is still enclosed in a portion of the cell's surface membrane and thus isolated from the cell's cytoplasm. The combined particle and membrane package is referred to as a food or phagocytic vacuole. See Vacuole

Ameboid cells of the metazoa also selectively remove foreign particles, bacteria, and other pathogens by phagocytosis. After the foreign particle or microorganism is trapped in a vacuole inside the macrophage, it is usually digested. To accomplish this, small packets (lysosomes) of lytic proenzymes are introduced into the phagocytic vacuole, where the enzymes are then dissolved and activated. See Lysosome

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Phagocytosis

 

the engulfing and absorption of living and nonliving particles by unicellular organisms or specialized cells—phagocytes—in multicellular animals. Phagocytosis was discovered by E. Metchnikoff (I. I. Mechnikov), who traced its evolution and elucidated its function in the defense reactions of the higher animals and man, particularly those related to inflammation and immunity. The process plays a major role in the healing of wounds.

The ability to seize and digest particles, which is the basis of nutrition in primitive organisms, was gradually transferred in the course of evolution to certain specialized cells—initially to the digestive cells and later to some special cells in the connective tissues. In mammals and in man, the neutrophils (that is, micro-phages, or specialized leukocytes) and the reticuloendothelial cells are active phagocytes capable of being transformed into active macrophages. The neutrophils phagocytize small particles, such as bacteria, while macrophages can ingest such larger particles as dead cells and their nuclei and fragments. Marcrophages can also store the negatively charged particles of pigments and of colloidal substances. The ingestion of small colloidal particles is called ultraphagocytosis.

Phagocytosis—a process that requires the expenditure of energy—involves primarily the activity of the cell membrane and intracellular organoids, or lysosomes, which have a high content of hydrolytic enzymes. Phagocytosis proceeds in stages. After a phagocytable particle has attached itself to the cell membrane, an intracellular corpuscle, or phagosome, is formed by invagination of the membrane and the particle. Hydrolytic enzymes enter the phagosome from the surrounding lysosomes and digest the phagocytized particle. Depending on the particle’s physiochemi-cal properties, digestion may be complete or incomplete. In the latter case, a residual corpuscle is formed and may remain in the cell a long time.

REFERENCES

Mechnikov, I. I. Izbrannye biologicheskie proizvedeniia. Moscow, 1950.
Zil’ber, L. A. Osnovy immunologii, 3rd ed. Moscow, 1958.

N. G. KHRUSHCHOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

phagocytosis

[‚fag·ə‚sī′tō·səs]
(cell and molecular biology)
A specialized form of macropinocytosis in which cells engulf large solid objects such as bacteria and deliver the internalized objects to special digesting vacuoles; exists in certain cell types, such as macrophages and neutrophils.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
In control samples without the test substance the percentage of phagocytosing PBP increased over time to just under 50% after 30 min.
The breakdown of thyroid hormones by phagocytosing leukocytes in an iodine-defincient patient could explain the high incidence of hypothyroxinemia in patients with chronic infections, such as chronic active hepatitis.
Actively phagocytosing hemocytes need to maintain their pseudopodia to adhere and internalize particles (Lane & Birkbeck 1999; Labreuche et al.
Phase (2) depicts PMNs phagocytosing crystals and releasing chemoattractants and NETs.
This suggests that macrophages can recognize larval cells before phagocytosing them.
Osteoclasts in turn are also capable of phagocytosing a wide size range of ceramic, polymeric, and metallic wear particles.
The diagnostic hallmark of MAS is the presence of well-differentiated, activated macrophages phagocytosing hematopoietic cells within the bone marrow.
This decrease in [O.sub.2.sup.-] generation by phagocytosing hemocytes was statistically significant; however, the NO synthase inhibitors (L-NMMA and L-NAME) did not significantly reduce [O.sub.2.sup.-] production (Table 1).
Phagocytes, which include hyaline amoebocytes (HA; actively phagocytosing cells) and macrophage-like cells (MLC) (Ballarin et al., 1994), have roundish nuclei and neutrophilic cytoplasm which, in the case of MLC, surrounds one or more vacuoles containing ingested material (Fig.
Dendritic cell and macrophages can both function in innate immunity by phagocytosing pathogens or innate immunity, but they also contribute to adaptive immune responses by serving as antigen-presenting cells for T cell activation [34].
Neutrophils are the first cells to migrate to the site of injury and are responsible for local cleaning, phagocytosing pathogens, and removing cellular debris.
They showed the tendency of reducing the "ripeness" of the female gonad, only few acini with oocytes were observed, associated to hemocytes, presumably phagocytosing them.