Langhans giant cells are immune cells composed of fused macrophages and form a typical component of inflammatory granulomas. Their exact function for the immune system has not yet been fully elucidated. They have been observed in the context of infections such as leprosy and chronic inflammations such as Crohn’s disease or sarcoidosis.
What are Langhans giant cells?
Macrophages are the scavenger cells of the immune system. They are motile and mononuclear cells of the cellular defense system. They arise in serum from circulating periphyton monocytes that can migrate into tissues and spend several weeks there as tissue macrophages. Macrophages can fuse into the so-called Langhans giant cells as part of a granulomatous inflammatory immune reaction. This immunological cell type is named after Theodor Langhans and thus after the director of the Institute of Pathology at the University of Bern. He coined the term giant cell in the 19th century, describing greatly enlarged cells with multiple nuclei. Although they were discovered more than a century ago and structurally well understood to this day, the exact function of Langhans giant cells in the context of immune defense is still not conclusively understood. Other cells in the giant cell group include Sternberg giant cells, foreign body giant cells, and osteoclasts or megakaryocytes. Similarly specialized macrophages are the so-called epithelial cells. Langhans giant cells belong to the inflammatory infiltrates, to which neutrophil granulocytes also belong.
Anatomy and structure
Langhans giant cells, like all other giant cells, have multiple nuclei and are highly enlarged cells with a diameter of approximately 0.3 millimeters. Foreign body giant cells arise from macrophage fusion as part of foreign body phagocytosis. Langhans giant cells can be distinguished from them anatomically on the basis of the marginal, horseshoe-shaped row to which their individual nuclei are subject in the cytoplasmic tissue. Some Langhans giant cells are equipped with Schaumann bodies and asteroid bodies. Schaumann bodies are round-oval inclusions of proteins and calcium that support a lamellar layer. Asteroid bodies, on the other hand, are present in star-shaped inclusions. Langhans giant cells a characteristic component of granuloma. These are the nodular tissue neoplasms that form in response to chronic inflammatory stimuli or allergies. In addition to giant cells and endothelial cells, they also contain epithelioid cells and mononuclear inflammatory cells such as lymphocytes or simple macrophages.
Function and Tasks
Fusion of macrophages into Langhans giant cells has been observed mainly in the context of granulomatous diseases. Such diseases can be of various causes. For example, the giant cells were detectable in infectious diseases such as leprosy, tuberculosis, and schistosomiasis. Langhans giant cells have also been detected as an inflammatory infilitrate of chronic inflammatory processes in Crohn’s disease, sarcoidosis and rheumatoid arthritis. The specific role of Langhans giant cells has not yet been scientifically elucidated. Presumably, they play a role mainly in the phagocytosis of specific antigens and can thus be classified as phagocytes. Phagocytosis is the uptake of extracellular solid particles and corresponds to a subtype of endocytosis. Phagocytes flow around foreign bodies in order to absorb them by invagination and constriction processes at the cell membrane. This results in the formation of large vesicles called phagosomes, which confluence with lysosomes. Thanks to lyosomal enzymes, phagosomes thus form phagolysosomes. Within the phagolysosome, the enzymatic degradation of ingested antigens begins. The phagocytosis of Langhans giant cells has been speculated mainly in the context of tuberculosis. Thus, in this disease, they presumably ingest the tuberculous Mycobacterium tuberculosis and render it harmless within themselves. However, since this phenomenon was only observed to a low degree of activity, the cells are mainly associated with the secretion of lysosomal enzymes. The only thing that is certain is their specialization in granulomatous inflammation and thus their immunological activity.
Diseases
Langhans giant cells are a component of many granulomatous diseases of chronic and acute nature.In the past, the enlarged cells from fused macrophages have been associated with diseases such as myositis, in addition to those mentioned above. This is an inflammatory disease of the skeletal muscles. Myositis is usually manifested by progressive loss of strength and weakness, mainly in the muscles close to the trunk. Dysphagia or muscle pain and wasting are also common symptoms. Sometimes calcium salts are deposited and cause metaplasia in the affected muscles. The result is muscle ossification. Autoimmune processes are being discussed as causes of myositis. In addition, this group of diseases is often associated with other primary diseases, which may be viral, bacterial or parasitic in nature. Leprosy and tuberculosis, for example, are associated with viral primary diseases. Because Langhans giant cells have been observed primarily in association with these two diseases, they also play a role in myositides such as tuberculotic myositis. Clinically, this form of myositis is manifested by swelling of the soft tissues. The tissue becomes necrotic and is colonized by Langhans giant cells. However, this form of myositis is extremely rare in Europe. Typical granulomas are again seen in lymph node tuberculosis. This disease shows central necrosis with epithelioid cells and the Langhans giant cells in circumference. Acid-fast rods are often found in the necrotic tissue. In contrast, in patients with poor immune defenses, the disease usually progresses without granuloma formation. In countries such as Asia, the above-mentioned diseases are a common phenomenon, unlike in Europe. Granulomatous reactions also occur in cases of syphilis, toxoplasmosis, fungal infections and parasitic infections. Granulomas have also been observed in carcinomas.