Which structure is characterized by tennis-racket-shaped cytoplasmic organelles found in Langerhans cells?

The tennis-racket-shaped cytoplasmic organelles found in Langerhans cells are known as Birbeck granules. These unique structures are characteristic of Langerhans cells, which are specialized dendritic cells involved in the immune response and are primarily found in the skin and mucosal tissues.

Birbeck granules are identifiable under an electron microscope due to their distinctive morphology, resembling a tennis racket or a rod with a handle. They play a role in antigen processing and presentation, which is crucial for the activation of T-cells in the immune response. These organelles contain proteins such as langerin, which is involved in the uptake of antigens.

Understanding the function and structure of Birbeck granules is important for recognizing the role of Langerhans cells in dermatopathology and immunology, which is pertinent for the USMLE Step 1 exam.

The other structures listed have different functions and are not specific to Langerhans cells. Weibel-Palade bodies are associated with endothelial cells and contain von Willebrand factor, while keratin intermediate filaments are integral components of the cytoskeleton in epithelial cells. Melanosomes are involved in the production and storage of melanin in melanocytes. Each of these structures