activated macrophage

macrophage

any of the large, mononuclear, highly phagocytic cells derived from bone marrow cells, promonocytes, the progeny of which, the monocytes, enter the bloodstream, where they stay for a few days before entering the tissues and developing into macrophages. They are components of the monocyte-macrophage system. Macrophages are usually immobile but become actively mobile when stimulated by inflammation, immune cytokines and microbial products. They are an important class of antigen presenting cells (APCs). See also immunity.

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activated macrophage

under the influence of cytokines, particularly γ-interferon and interleukin 4, released by antigen-stimulated Th1 lymphocytes, resting macrophages are activated whereby they become larger, more motile, stickier, express more MHCII proteins on their surface, contain more lysosomes and lysosomal enzymes, and secrete a variety of substances including interleukin 1, tumor necrosis factors; they have increased phagocytic activity and increased killing via reactive oxygen intermediates, collagenases and lysosomal enzymes. Called also angry macrophage.

macrophage activating factor (MAF)

a lymphokine produced by T lymphocytes following in vitro, probably γ-interferon, antigenic stimulation that activates macrophages.

alveolar m's

rounded, granular, mononuclear phagocytes within the alveoli of the lungs that ingest inhaled particulate matter.

angry macrophage

see activated macrophage (above).

armed m's

those capable of inducing cytotoxicity as a consequence of binding antibodies via Fc receptors on their surfaces or by factors derived from T lymphocytes (specific macrophage arming factor [SMAF]).

macrophage chemotactic factor (MCF)

a lymphokine that attracts macrophages.

macrophage colony-stimulating factor

see colony-stimulating factors.

macrophage inhibition factor (MIF)

a lymphokine that inhibits macrophage migration, causing them to accumulate at the site of antigen.

specific macrophage arming factor (SMAF)

a lymphokine that stimulates macrophage cytotoxic activity.

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activated macrophage

Immunology A mononuclear phagocyte that has been 'turned on'–ie has enhanced activity by cytokines; AMs are bigger–twice the size of resting macrophages and 'badder'–↑ lysozymes and surface expression of MHC class II antigens, and are pivotal in defending against microorganisms that grow well in histiocytes/tissue-based macrophages and other cells–eg, Listeria spp, and Salmonella spp