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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.
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 ...
[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. [9]
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]
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] When a phagocytic cell engulfs bacteria, a phagosome is formed around it and the entire complex is ultimately trafficked to the lysosome for degradation.
Stimulating cells to secrete a variety of cytokines that influence the function of other cells involved in adaptive immune responses and innate immune responses. [3] [4] Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells.
In immunology, the mononuclear phagocyte system or mononuclear phagocytic system (MPS) also known as the macrophage system is a part of the immune system that consists of the phagocytic cells [1] located in reticular connective tissue. The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen.