THE STORY OF BIRBECK GRANULES.

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Birbeck granules also known as Birbeck bodies are rod-shaped structures of variable length with a central, periodically striated lamella. The origin and function of these granules is still a debate.They are specific to Langerhans cells and not seen in other dendritic cells.

It was first described in 1961 by Michael Stanley Clive Birbeck. Michael Birbeck  was a British scientist and electron microscopist. He worked at the Institute of Cancer Research (Chester Beatty Cancer Research Institute), London from 1950 to 1981. Birbeck granules are seen in normal langerhans granules. However, they are used to differentiate Langerhans cell histiocytoses from other proliferative disorders.

The formation of these granules is induced by langerin. These structures form from the accumulation of C-type lectin Langerin (CD207)  and appears to be related to endosomal trafficking.  

Langerin immunostain has replaced the need of ultrastructural analysis. Ultrastructurally, Birbeck granule is a rod-shaped bilaminar disk with an internal zipper-like pattern of situations, often with a bulbous dilatation at one end, resembles a tennis raquet hence called tennis raquet appearance.


                                              Electron microscopic picture showing Birbeck granules.

The two most commonly debated origins are secretory and endocytic. In the secretory model, the granules bud from the Golgi stacks and fuse with the plasma membrane, exocytosing their putative contents. In the endocytic model, the granules invaginate from the plasma membrane, bringing antigens and/or nutrients into the cell.  But its still a debate on the function of Birbeck granules.

Hope you find it interesting.

See you with some exciting posts soon.


REFERENCES:
1.     https://www.sciencedirect.com/topics/medicine-and-dentistry/birbeck-granules
2.    Ray Mc Dermott, Umit Ziylan, Danie le Spehner. Birbeck Granules are subdomains of Endosomal recycling Compartment in Human epidermal Langerhans Cells, which form where Langerin Accumulates. Molecular Biology of the Cell. 2002:13;317–335.
3.    Picture taken from https://en.wikipedia.org/wiki/Birbeck granules

                                                                            Written by Dr.Priyavadhana

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