Langerhans cells: uptake of tritiated thymidine.

After irradiation of the skin of the rhesus monkey with ultraviolet light, there is temporary suppression of the proliferating activity of the epidermal cells, followed by some hyperplasia and a striking increase in synthesis of DNA by Langerhans cells. Since Langerhans cells can proliferate, they can no longer be considered to be worn-out melanocytes.