Migration and Maturation of Langerhans Cells in Skin Transplants and Explants

The behavior of Langerhans cells (LC) has been examined after skin transplantation and in an organ culture system. Within 24 h (and even within 4 h of culture), LC in epidermal sheets from allografts, isografts, and explants dramatically increased in size and expression of major histocompatibility complex class II molecules, and their numbers were markedly decreased. Using a new procedure, dermal sheets were then examined. By 24 h, cells resembling LC were found close to the epidermal-dermal junction, and by 3 d, they formed cords in dermal lymphatics before leaving the skin. In organ culture, the cells continued to migrate spontaneously into the medium. These observations establish a direct route for migration of LC from the epidermis into the dermis and then out of the skin. These processes are apparently i…