Effects of sunlight exposure on Langerhans cells and melanocytes in human epidermis.

The effects of 12 daily, half-hour exposures to sunlight on epidermal Langerhans cells (LC), and melanocytes were studied in 31 healthy volunteers. Nineteen were of Celtic and 12 of mixed European descent. Sunlight appeared to have both a direct, transient, detrimental effect and an indirect stimulating effect on the LC, and a direct and an indirect stimulating effect on the melanocytes. The mixed Europeans had a somewhat greater increase in the melanocyte population density following exposure to sunlight than the Celts. However, the number of LC fell following sunlight exposure regardless of the melanocyte response. Thus the melanocytes did not appear to provide the LC with immediate protection from ultraviolet light.