Birbeck granules

Birbeck granules are rod-shaped organelles found in Langerhans cells.

Birbeck granules are distinctive rod-shaped or "tennis racket"-shaped organelles found in Langerhans cells, which are a type of dendritic cell located in the epidermis and other tissues. These granules are considered a hallmark of Langerhans cells and are used as a diagnostic feature in identifying these cells under the electron microscope.

Structure and Appearance

Birbeck granules are characterized by their unique morphology. They typically appear as rod-shaped structures with a central striated core and a terminal bulb, giving them a "tennis racket" appearance. The granules measure approximately 30-40 nm in diameter and can be up to 1 μm in length. The striated core is thought to be composed of langerin, a protein that is involved in the formation of these granules.

Function

The exact function of Birbeck granules is not fully understood, but they are believed to play a role in the processing and presentation of antigens by Langerhans cells. Langerin, the protein associated with Birbeck granules, is a C-type lectin receptor that binds to specific carbohydrates on the surface of pathogens. This binding is thought to facilitate the internalization and processing of antigens, which are then presented to T cells to initiate an immune response.

Clinical Significance

Birbeck granules are used as a diagnostic marker for Langerhans cells in various conditions, including Langerhans cell histiocytosis (LCH), a rare disorder characterized by the proliferation of Langerhans cells. The presence of Birbeck granules can be confirmed through electron microscopy, aiding in the diagnosis of LCH and distinguishing it from other histiocytic disorders.

History

Birbeck granules were first described in 1961 by Michael S. Birbeck and his colleagues, who identified these structures in Langerhans cells using electron microscopy. Their discovery provided significant insights into the unique features of Langerhans cells and their role in the immune system.

Also see

• Langerhans cell
• Langerhans cell histiocytosis
• Dendritic cell
• Electron microscopy
• Langerin

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  Langerhans cell histiocytosis - Birbeck granules