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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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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



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.


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



(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.
References in periodicals archive ?
Our data indicated that 30 [+ or -] 3.2% of the drug-treated cells were able to phagocytize the latex particles after 72 h of exposure to 1.5 [micro]g/ml of the new compound.
Immunization with the compound is believed to stimulate formation of antibodies directed at the protein and to trigger microglial cells and monocytes to phagocytize amyloid deposits in the brain, he said.
A study showed that individuals with Down's syndrome have impaired neutrophil chemotaxis.[11] Due to this impairment, the neutrophils are unable to get to the diseased area to phagocytize the disease-causing microorganisms.
Inflammatory cells such as polymorphonuclear cells increase in the joint space and phagocytize the immune complexes (McCance & Huether, 1994).
Neutrophils phagocytize the offending substance and release factors that summon other leukocytes and lymphocytes.
Proximal tubule cells have been reported to actively phagocytize erythrocytes in renal injury (Madsen et al.
The capacity of mouse peritoneal macrophages to phagocytize fluorescein-labelled latex beads was carried out as described previously (Torres-Santos et al.
They are not able to phagocytize. In monoculture, JKT cells responded to a limited number of stimuli including phorbol ester, phytohemagglutinin, metals, formaldehyde, calcium ionophores, and pyrene, but not to hydrogen peroxide or mitomycin C (Brundage et al.
After spawning, NPs may phagocytize residual ova or spermatozoa and may recycle nutrients derived in this way (Pearse, 1969b).
Clasmatocyte-like cells, located in the partitions between the alveoli--their origin was not followed--begin to phagocytize the carbon.
Macrophages phagocytize particles and secrete proinflammatory factors such as tumor necrosis factor-[alpha] (TNF-[alpha]), which are thought to mediate the differentiation of osteoclast precursor cells and play a fundamental role in this pathologic response (5,6).
During EAE, activated microglia are known to phagocytize myelin debris and oligodendrocytes in lesions, which in turn leads to the release of proinflammatory cytokines [71, 73] (Figure 1).