Langerhans cell histiocytosis - Birbeck granules

Birbeck granules, also known as Birbeck bodies, are rod shaped or "tennis-racket"

cytoplasmic The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell and ...

organelles In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' th ...

found only in

Langerhans cells A Langerhans cell (LC) is a tissue-resident macrophage of the skin once thought to be a resident dendritic cell. These cells contain organelles called Birbeck granules. They are present in all layers of the epidermis and are most prominent in ...

. Their appearance on electron microscopy is with a central linear density and a striated appearance. Although part of normal Langerhans cell histology, they also provide a mechanism to differentiate Langerhans cell histiocytoses (which are a group of rare conditions collectively known as histiocytoses) from proliferative disorders caused by other cell lines. Synthesis of Birbeck granules is mediated by

langerin Langerin (CD207) is a type II transmembrane protein which is encoded by the ''CD207'' gene in humans. It was discovered by scientists Sem Saeland and Jenny Valladeau as a main part of Birbeck granules. Langerin is C-type lectin receptor on Lan ...

Function

The function of Birbeck granules is debated, but one theory is that they migrate to the periphery of the

and release their contents into the extracellular matrix. Another theory is that the Birbeck granule functions in

receptor-mediated endocytosis Receptor-mediated endocytosis (RME), also called clathrin-mediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane (invagination). This ...

, similar to

clathrin Clathrin is a protein that plays a role in the formation of coated vesicles. Clathrin was first isolated by Barbara Pearse in 1976. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskel ...

-coated pits.

Role in medical diagnostics

For decades, identification of Birbeck granules via

electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

was the only reliable way to diagnose

Langerhans cell histiocytosis Langerhans cell histiocytosis (LCH) is an abnormal clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes. Symptoms range from isolated bone lesions to multisystem d ...

. Later,

immunohistochemical staining Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Albert Hewett ...

of CD207 (Langerin) provided a more cost-effective way to diagnose the condition. As a result, the reliance on visual identification of Birbeck granules has decreased over time.

History

Birbeck granules were discovered by Michael Stanley Clive Birbeck (1925–2005), a British scientist and electron microscopist who worked at the Chester Beatty Cancer Research Institute or

Institute of Cancer Research The Institute of Cancer Research (the ICR) is a public research institute and a member institution of the University of London in London, United Kingdom, specialising in oncology. It was founded in 1909 as a research department of the Royal Ma ...

, London from 1950 until 1981.

References

External links

Image at ouhsc.edu

Image at humpath.com
Monocyte- and macrophage-related cutaneous conditions {{cell-biology-stub