Giant multinucleated cell
Encyclopedia
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
.
of the alveolus, immune cells known as macrophages identify 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 lysosome
to create a phagolysosome
. In the phagolysosome, the cell attempts to use reactive oxygen species
and acid to kill the bacterium. However, M. tuberculosis has a thick, waxy mycolic acid
capsule 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.
(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.
Acid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...
bacterium Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...
, the causative agent of the disease tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
.
Formation
Following inhalation of the M. tuberculosis bacterium and its attachment to the lumenLumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
of the alveolus, immune cells known as macrophages identify 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
Phagosome
In cell biology, a phagosome is a vacuole formed around a particle absorbed by phagocytosis. The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested...
. The phagosome then combines with a lysosome
Lysosome
thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...
to create a phagolysosome
Phagolysosome
A phagolysosome is the membrane-enclosed organelle which forms when a phagosome fuses with a lysosome. After fusion, the food particles or pathogens contained within the phagosome are usually digested by the enzymes contained within the lysosome. Phagolysosome formation follows phagocytosis...
. In the phagolysosome, the cell attempts to use reactive oxygen species
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....
and acid to kill the bacterium. However, M. tuberculosis has a thick, waxy mycolic acid
Mycolic acid
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species...
capsule 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 necrotic and dies. However, the M. tuberculosis bacterium inside is still viable. When the periphery of the giant multinucleated cell becomes calcified, a tuberculeGranuloma
Granuloma is a medical term for a tiny collection of immune cells known as macrophages. Granulomas form when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate. Such substances include infectious organisms such as bacteria and fungi as well as...
(also known as a granuloma
Granuloma
Granuloma is a medical term for a tiny collection of immune cells known as macrophages. Granulomas form when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate. Such substances include infectious organisms such as bacteria and fungi as well as...
) 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.