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Micrograph showing hemosiderin-laden alveolar macrophages, as seen in a pulmonary hemorrhage. H&E stain. An alveolar macrophage, pulmonary macrophage, (or dust cell) is a type of macrophage, a professional phagocyte, found in the airways and at the level of the alveoli in the lungs, but separated from their walls. [1]
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.
Macrophages are phagocytic cells that are produced during an injury or infection. [1] They defend against infectious microorganisms, but also play a role in homeostasis and wound healing . [ 1 ] Through the release of Interleukin 4 (IL-4) and Interleukin 13 (IL-13) by TH2, or T helper cells , and mast cells , these macrophages can fuse to form ...
Macrophages can also recognize pathogens for phagocytosis indirectly through opsonins, which are molecules that attach to pathogens and mark them for phagocytosis. [29] Opsonins can cause a stronger adhesion between the macrophage and pathogen during phagocytosis, hence opsonins tend to enhance macrophages’ phagocytic activity. [30]
Phagocytes occur in many species; some amoebae behave like macrophage phagocytes, which suggests that phagocytes appeared early in the evolution of life. [6] Phagocytes of humans and other animals are called "professional" or "non-professional" depending on how effective they are at phagocytosis. [7]
The major function of the lungs is gas exchange between the lungs and the blood. [67] The alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier . [ 34 ] [ 68 ] [ 69 ] This thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates ...
They are mobile scavengers that serve to engulf foreign particles in the lungs, such as dust, bacteria, carbon particles, and blood cells from injuries. [24] They are also called pulmonary macrophages, and dust cells. Alveolar macrophages also play a crucial role in immune responses against viral pathogens in the lungs. [25]
However, macrophages, especially alveolar macrophages, usually produce far lower levels of ROS than neutrophils, and may require activation for their bactericidal properties. Instead, their transient oxidative burst regulates the inflammatory response by inducing cytokine synthesis for redox signalling, resulting in an influx of neutrophils and ...