Self-renewal capacity of human epidermal Langerhans cells: observations made on a composite tissue allograft

: Epidermal Langerhans cells (LC) are dendritic, antigen‐presenting cells residing within mammalian epidermis and mucosal epithelia. When massively depleted, they are replaced by cells of bone‐marrow origin. However, their renewal within normal skin under steady‐state conditions is not precisely known. We observed that epidermal LC within a human hand allograft remain stable in the long term (10 years) and are not replaced by cells of recipient’s origin; furthermore, we observed a Langerhans cell in mitosis within the epidermis 8 years postgraft. These results show that under almost physiological conditions, human LC renew in the epidermis by local mitoses of preexisting cells.