Birbeck granules

Birbeck granules are small, characteristic structures found inside certain immune cells called Langerhans cells. These granules appear as rod- or tennis racket-shaped bodies under a microscope. They are involved in the immune system's response, helping Langerhans cells capture and process antigens—substances that trigger immune reactions. Birbeck granules are considered a distinctive feature used by pathologists to identify Langerhans cells in tissue samples, aiding in diagnoses of specific diseases like Langerhans cell histiocytosis. Their exact functional role is still being studied, but they are hallmark indicators of these specialized immune cells.