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Macrophages are diffusely scattered in the connective tissue and in liver (Kupffer cells), spleen and lymph nodes (sinus histiocytes), lungs (alveolar macrophages), and central nervous system (microglia). The half-life of blood monocytes is about 1 day, whereas the life span of tissue macrophages is several months or years.
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 ...
Overview of phagocytosis Phagocytosis versus exocytosis. 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 macrophage's location can determine its size and appearance. Macrophages cause inflammation through the production of interleukin-1, interleukin-6, and TNF-alpha. [75] Macrophages are usually only found in tissue and are rarely seen in blood circulation. The life-span of tissue macrophages has been estimated to range from four to fifteen days ...
Honoured as the "father of innate immunity", [16] [17] Metchnikoff was the first to discover a process of immunity called phagocytosis and the cell responsible for it, called phagocyte, specifically macrophage, in 1882.
It has been known for some time that animals defend themselves against cancer by antibody-mediated or antibody-independent phagocytosis of viable tumour cells by macrophages. Recognition of viable cancer cells for phagocytosis may be based on the expression of novel antigens, senescence markers, phosphatidylserine or calreticulin.
The first demonstration of phagocytosis as a property of leukocytes, the immune cells, was from the German zoologist Ernst Haeckel. [14] [15] In 1846, English physician Thomas Wharton Jones had discovered that a group of leucocytes, which he called "granule-cell" (later renamed and identified as eosinophil [16]), could change shape, the phenomenon later called amoeboid movement.
Phagocytosis of a bacterium, showing the formation of phagosome and phagolysosome 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).