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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]
Alveolar surfactant has a half-life of 5 to 10 hours once secreted. It can be both broken down by macrophages and/or reabsorbed into the lamellar structures of type II pneumocytes. Up to 90% of surfactant DPPC (dipalmitoylphosphatidylcholine) is recycled from the alveolar space back into the type II pneumocyte.
Smoker's macrophages are alveolar macrophages whose characteristics, including appearance, cellularity, phenotypes, immune response, and other functions, have been affected upon the exposure to cigarettes. [1] These altered immune cells are derived from several signaling pathways and are able to induce numerous respiratory diseases.
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.
The surfactant reduces the surface tension at the air-alveolar surface which allows expansion of the alveolar sacs. The alveolar sacs contain the primitive alveoli that form at the end of the alveolar ducts, [ 60 ] and their appearance around the seventh month marks the point at which limited respiration would be possible, and the premature ...
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] They secrete cytokines and chemokines, which recruit and activate other immune cells, initiate type I interferon signaling, and inhibit the nuclear export of viral genomes. [25]
[2] [9] Lipid-laden alveolar macrophages have been reported in cases of vaping-associated pulmonary injury. [10] [1] [11] The lipid-laden macrophage index (LLMI) can be calculated by counting 100 macrophages in a BAL specimen treated with a lipid stain and scoring each macrophage from 0 to 4 based on the amount of lipids present in the cell.
Macrophages are found in essentially all tissues, [4] 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.