Macrophages (abbreviated as Mφ, MΦ or MP) (Greek: large eaters, from Greek μακρός (makrós) = large, φαγεῖν(phagein) = to eat) are a type of white blood cell of the immune system that engulfs and digests anything that does not have, on its surface, proteins that are specific to healthy body cells, including cancer cells, microbes, cellular debris, foreign substances, etc.[2][3] The process is called phagocytosis, which acts to defend the host against infection and injury.[4]
These large phagocytes are found in essentially all tissues,[5] where they patrol for potential pathogens by amoeboid movement. 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 (adaptive immunity) by recruiting other immune cells such as lymphocytes. For example, they are important as antigen presenters to T cells. In humans, dysfunctional macrophages cause severe diseases such as chronic granulomatous disease that result in frequent infections.
Beyond increasing inflammation and stimulating the immune system, macrophages also play an important anti-inflammatory role and can decrease immune reactions through the release of cytokines. Macrophages that encourage inflammation are called M1 macrophages, whereas those that decrease inflammation and encourage tissue repair are called M2 macrophages.[6] This difference is reflected in their metabolism; M1 macrophages have the unique ability to metabolize arginine to the "killer" molecule nitric oxide, whereas M2 macrophages have the unique ability to metabolize arginine to the "repair" molecule ornithine.[7] However, this dichotomy has been recently questioned as further complexity has been discovered.[8]
Human macrophages are about 21 micrometres (0.00083 in) in diameter[9] and are produced by the differentiation of monocytes in tissues. They can be identified using flow cytometry or immunohistochemical staining by their specific expression of proteins such as CD14, CD40, CD11b, CD64, F4/80 (mice)/EMR1 (human), lysozyme M, MAC-1/MAC-3 and CD68.[10]
Macrophages were first discovered by Élie Metchnikoff, a Russian zoologist, in 1884.[11]
Macrophage
Details
Pronunciation/ˈmakrə(ʊ)feɪdʒ/SystemImmune system
FunctionPhagocytosis
IdentifiersLatinMacrophagocytusAcronym(s)Mφ, MΦ
MeSHD008264THH2.00.03.0.01007 FMA63261
Anatomical terms of microanatomy
https://en.wikipedia.org/wiki/Macrophage
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