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Phagocytosis (from Ancient Greek φαγεῖν (phagein) 'to eat' and κύτος (kytos) 'cell') is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte.
[23] [24] Phagocytosis occurs after the foreign body, a bacterial cell, for example, has bound to molecules called "receptors" that are on the surface of the phagocyte. The phagocyte then stretches itself around the bacterium and engulfs it. Phagocytosis of bacteria by human neutrophils takes on average nine minutes. [25]
Phagoptosis is normally caused by: the cell exposing on its surface so-called "eat-me" signals, and/or the cell no longer exposing "don't-eat-me" signals and/or the cell being opsonised i.e. binding soluble proteins that tag the cell for phagocytosis. For example, phosphatidylserine is an "eat-me" signal that, when exposed on the surface of a ...
The Human Cell Atlas project, which started in 2016, had as one of its goals to "catalog all cell types (for example, immune cells or brain cells) and sub-types in the human body". [13] By 2018, the Human Cell Atlas description based the project on the assumption that "our characterization of the hundreds of types and subtypes of cells in the ...
When host cells die, either by apoptosis or by cell injury due to an infection, phagocytic cells are responsible for their removal from the affected site. [9] By helping to remove dead cells preceding growth and development of new healthy cells, phagocytosis is an important part of the healing process following tissue injury. A macrophage
Macrophages, neutrophils, and dendritic cells are all cells of the innate immune system that utilize phagocytosis and are equipped with Toll-like receptors (TLR). Toll-like receptors are present on each of these cells and recognize a variety of microbial products resulting in the induction of more specific immune responses. [2]
Due to their role in phagocytosis, macrophages are involved in many diseases of the immune system. For example, they participate in the formation of granulomas, inflammatory lesions that may be caused by a large number of diseases. Some disorders, mostly rare, of ineffective phagocytosis and macrophage function have been described, for example.
With a diameter of 15–22 μm, monocytes are the largest cell type in peripheral blood. [2] [3] Monocytes are mononuclear cells and the ellipsoidal nucleus is often lobulated/indented, causing a bean-shaped or kidney-shaped appearance. [4] Monocytes compose 2% to 10% of all leukocytes in the human body.