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The engulfing of a pathogen by a phagocyte. In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized.
Some phagocytes kill the ingested pathogen with oxidants and nitric oxide. [12] After phagocytosis, macrophages and dendritic cells can also participate in antigen presentation, a process in which a phagocyte moves parts of the ingested material back to its surface. This material is then displayed to other cells of the immune system.
Phagoptosis is a major form of host defence against pathogens and cancer cells. However, recent evidence indicates that excessive phagoptosis may kill host cells in inflammatory conditions, contributing to haemophagic conditions, and neuronal loss in the inflamed brain. [1]
Macrophages can also recognize pathogens for phagocytosis indirectly through opsonins, which are molecules that attach to pathogens and mark them for phagocytosis. [29] Opsonins can cause a stronger adhesion between the macrophage and pathogen during phagocytosis, hence opsonins tend to enhance macrophages’ phagocytic activity. [ 30 ]
Monocytes, the largest type of white blood cell, share the "vacuum cleaner" (phagocytosis) function of neutrophils, but are much longer lived as they have an extra role: they present pieces of pathogens to T cells so that the pathogens may be recognized again and killed. This causes an antibody response to be mounted.
Scheme of the complement system. The complement system, also known as complement cascade, is a part of the humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. [1]
Most studies do not image the process of phagocytosis to completion, instead using lysosome fusion or acidification of the phagolysosome lumen as endpoints. [9] Additionally, this resolution stage is less well understood compared to earlier phases of phagocytosis, as it can take a significant amount of time. While engulfment and phagosome ...
The mononuclear phagocyte system is part of both humoral and cell-mediated immunity. The mononuclear phagocyte system has an important role in defense against microorganisms, including mycobacteria, fungi, bacteria, protozoa, and viruses. Macrophages remove senescent erythrocytes, leukocytes, and megakaryocytes by phagocytosis and digestion.