Development




Macrophages that reside in adult healthy tissues either derive from circulating monocytes or are established before birth and then maintained during adult life independently of monocytes. By contrast, most of the macrophages that accumulate at diseased sites typically derive from circulating monocytes. When a monocyte enters damaged tissue through the endothelium of a blood vessel, a process known as leukocyte extravasation, it undergoes a series of changes to become a macrophage. Monocytes are attracted to a damaged site by chemical substances through chemotaxis, triggered by a range of stimuli including damaged cells, pathogens and cytokines released by macrophages already at the site. At some sites such as the testis, macrophages have been shown to populate the organ through proliferation.citation needed Unlike short-lived neutrophils, macrophages survive longer in the body, up to several months.

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Macrophage

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Clinical significance

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Function

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