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( Macrophage)
Macrophages (Greek "big eaters", from makros "large" + phagein "eat") (mø[1]) are cells within the tissues that originate from specific white blood cells called monocytes. Monocytes and macrophages are phagocytes, acting in both non-specific defense (or innate immunity) as well as specific defense (or cell-mediated immunity) of vertebrate animals. Their role is to phagocytose (engulf and then digest) cellular debris and pathogens either as stationary or mobile cells, and to stimulate lymphocytes and other immune cells to respond to the pathogen. When a monocyte enters damaged tissue through the endothelium of a blood vessel (a process known as the leukocyte adhesion cascade), 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, histamine released by mast cells and basophils, 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. Unlike short-lived neutrophils, macrophages survive longer in the body up to a maximum of several months. One important role of the macrophage is the removal of necrotic cellular debris in the lungs. Removing dead cell material is important in chronic inflammation as the early stages of inflammation are dominated by neutrophil granulocytes, which are ingested by macrophages if they come of age (see CD-31 for a description of this process.)
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Macrophage Subcategories
Macrophage Articles
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