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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 ?
3 shows that despite a transient increase in phagocytosis at 20 [micro]g/ml, the oleanolic acid significantly decreased the capacity of macrophages to phagocytize fluoresceinated latex beads at higher concentrations, indicating that the toxicity of oleanolic acid is not restricted to the leishmania parasites.
As digestion proceeds, certain cells lining the digestive diverticula phagocytize the plastids into intracellular vacuoles.
For example, when a foreign substance is identified, lymphocytes called macrophages phagocytize the antagonist substances and break them up into fragments which are then exposed at the surface of the macrophage and presented to the immunoregulator T lymphocytes.
Clasmatocyte-like cells, located in the partitions between the alveoli--their origin was not followed--begin to phagocytize the carbon.
virginica's ability to recognize and phagocytize it as an invasion mechanism.
yamazii, microorganisms invade through the wounded part before the completion of cuticle regeneration, phagocytic tunic cells might be expected to phagocytize those invaders (Hirose et al.
The efficacy of this clearance mechanism depends highly on the efficiency of alveolar macrophages to "sense" deposited particles, move to the site of their deposition, and then phagocytize them.
Third-type cells may phagocytize trapped matter and secrete antibacterial lysins (Bang and Bang, 1962; Dybas, 1981a).
We made ultrastructural observations and compared human blood monocyte-derived macrophages (MDMs; known to avidly phagocytize PM) with human T-cells (as nonphagocytic controls) on exposure to C or C/Fe particulates.
piscicida has the capacity to phagocytize blood cells and cause tissue injury (2), it may initiate an acute inflammation that is potentiated to a chronic response by pPfTx, behaving as a potent ATP mimic at P2X7 receptors on activated macrophages.
A nearby macrophage or epithelial cell phagocytizes the pseudopod and Listeria bacteria tunnel out of the cell that engulfed it and continue to survive as an intracellular parasite in the new host cell.
Polymorphonuclear leukocyte Phagocytizes invading microbes and kills them