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This cytokine—a class of signaling molecule [39] —kills cancer cells and cells infected by viruses, and helps to activate the other cells of the immune system. [ 40 ] In some diseases, e.g., the rare chronic granulomatous disease , the efficiency of phagocytes is impaired, and recurrent bacterial infections are a problem. [ 41 ]
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.
NK cells also kill tumorous cells in a similar way, especially if the tumor cells have fewer MHC class I molecules on their surface than normal; this is a common phenomenon with tumors. [144] Sometimes antibodies are generated against tumor cells allowing for their destruction by the complement system. [139]
Other non-professional phagocytes have some degree of phagocytic activity, such as thyroid and bladder epithelial cells that can engulf erythrocytes and retinal epithelial cells that internalise retinal rods. [8] However non-professional phagocytes do not express specific phagocytic receptors such as FcR and have a much lower rate of ...
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
[9] The phagocyte then engulfs the extracellular pathogen or particle, entrapping it within its membrane. Phagocytic Cup Formation: Upon signal recognition, additional receptors are recruited to the site, and the phagocyte's plasma membrane begins to extend around the target, forming a structure called the phagocytic cup.
Activation of phagocytes is the most common function attributed to Fc receptors. For example, macrophages begin to ingest and kill an IgG-coated pathogen by phagocytosis following engagement of their Fcγ receptors. [24] Another process involving Fc receptors is called antibody-dependent cell-mediated cytotoxicity (ADCC).
The phagocytes interact with the dying cells through the presenting eat-me signals through specific eat-me signal receptors on the phagocytic cell. [23] The phagocyte will engulf the eat-me signal presenting cell through induced signaling of engulfment receptors and by the reorganization of the phagocytic cell's cytoskeleton. [24] The ...