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In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs). [1] A phagosome is formed by the fusion of the cell membrane around a microorganism, a senescent cell or an apoptotic cell.
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.
The phagocyte then stretches itself around the bacterium and engulfs it. Phagocytosis of bacteria by human neutrophils takes on average nine minutes. [25] Once inside this phagocyte, the bacterium is trapped in a compartment called a phagosome. Within one minute the phagosome merges with either a lysosome or a granule to form a phagolysosome.
Phagosome Formation: Once the phagocytic cup has almost completely surrounded the target, the membrane extensions seal together, forming an intact phagosome containing the engulfed material. [9] Phagosome Maturation: The newly formed phagosome undergoes a series of transitions similar to endosome maturation. This process involves the recycling ...
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system. Besides phagocytosis, they play a critical role in nonspecific defense ( innate immunity ) and also help initiate specific defense mechanisms ...
Once a pathogen has been engulfed by a phagocyte, it becomes trapped in an intracellular vesicle called a phagosome, which subsequently fuses with another vesicle called a lysosome to form a phagolysosome. The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome.
In detail, a phagocyte's duty is obtaining food particles and digesting it in a vacuole. [2] For example, following phagocytosis, the ingested particle (or phagosome) fuses with a lysosome containing hydrolytic enzymes to form a phagolysosome; the pathogens or food particles within the phagosome are then digested by the lysosome's enzymes.
1) Antibodies (A) and pathogens (B) circular in the blood. 2) The antibodies bind to pathogens with complementary antigen sequences, engaging in opsonization (2a), neutralisation (2b), and agglutination (2c). 3) A phagocyte (C) approaches the pathogen, and Fc region (D) of the antibody binds to one of the Fc receptors (E) on the phagocyte.