- Giant multinucleated cell
Giant multinucleated cells are seen in the early stages of active infection with the
acid-fast bacterium" Mycobacterium tuberculosis", the causative agent of the disease tuberculosis.
Following inhalation of the "M. tuberculosis" bacterium and its attachment to the lumen of the
alveolus, immune cellsknown as macrophagesidentify the bacterium as "foreign" and attempt to eliminate it by phagocytosis. During this process, the entire bacterium is enveloped by the macrophage and stored temporarily in a membrane-bound vesicle called a phagosome. The phagosome then combines with a lysosometo create a phagolysosome. In the phagolysosome, the cell attempts to use reactive oxygen speciesand acid to kill the bacterium. However, "M. tuberculosis" has a thick, waxy mycolic acidcapsule that protects it from these toxic substances. "M. tuberculosis" actually reproduces inside the macrophage and will eventually kill the immune cell. Other macrophages attack the infected macrophage, fusing together to form a giant multinucleated cell in the alveolar lumen.
Transformation into tubercules
The giant multinucleated cell eventually becomes
necroticand dies. However, the "M. tuberculosis" bacterium inside is still viable. When the periphery of the giant multinucleated cell becomes calcified, a tubercule(also known as a granuloma) is formed, which remains in the lungs and may eventually need to be surgically excised. The giant multinucleated cell can also liquefy and spread the bacterial infection to the blood or other tissues.
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