Langerin expression and Birbeck granules are hallmarks of Langerhans cells. (A) Conventional fluorescence microscopy of an epidermal sheet prepared from healthy human skin. Langerhans cells are immunolabeled with anti-CD207/langerin monoclonal antibody (Miltenyi Biotec). Scale bar, 30 µm. (B) Detail from a transmission electron micrograph of a human epidermal Langerhans cell in situ featuring 2 tennis racket–shaped Birbeck granules. Scale bar, 60 nm.