Most efficient antigen presenting cell in the skin -

Langerhans cells are dendritic cells (antigen-presenting immune cells) of the skin and mucosa, and contain large organelles called Birbeck granules. They are present in all layers of the epidermis except the stratum corneum, which protects against infections, and are most prominent in the stratum spinosum. Reff: Ananthanarayanan & Panikers textbook of microbiology 9th edition pg: 138