Transmission electron micrograph of Langerhans' cells. Langerhans' cells are located in all layers of the epidermis but are most easily seen in the prickle cell layer. They recognize antigen and are an important component of the immune system. Ultrastructurally, Langerhans' cells have an irregular clefted nucleus and are devoid of tonofilaments. They have prominent mitochondria, lysosmes and rough endoplasmic reticulum. Birbeck granules are not seen in this magnification.