Cored tubules are present in human epidermal Langerhans cells

Cored tubules are ultrastructural organelles described to date only in murine cells belonging to the Langerhans cell family and located in the dermis and its draining lymph nodes. These organelles, the function of which is unknown, differ from Birbeck granules and are interestingly not found in murine epidermal Langerhans cells. In this work we demonstrate that cored tubules are present in freshly isolated human epidermal Langerhans cells. The tubules were found to be interconnected with structures known to belong to the early endosomal pathway and could be immunolabeled with gold-conjugated anti-CD1a and anti-Langerin monoclonal antibodies, but only at 37 degrees C. At this temperature such antibodies are able to progress from the early sorting endosomes to the early recycling endosomes, which in human Langerhans cells include the Birbeck granules. These findings strongly suggest that cored tubules form part of the early recycling compartment.