UV-related skin conditions and Langerhans' cell populations in human skin.

Chronic sun exposure and cumulative exposures to PUVA are associated with a risk of development of non-melanoma skin cancer. Acute UV irradiation reduces the number of epidermal antigen-presenting Langerhans' cells in the skin. Alterations in the Langerhans' cell population could be relevant to a disturbance in the cutaneous immune response in UV-exposed skin. Therefore the density of CDla+ and ATPase+ Langerhans' cells in epidermal sheets from the hand, buttock and in some cases face was examined in PUVA-treated patients (n = 8) and in patients with actinic keratosis (n = 13) or basal cell carcinoma (n = 16). The number of Langerhans' cells was significantly lower on the hand compared with that on the face and buttock (p < 0.05). There was no difference in Langerhans' cell distribution between the different diagnostic groups and controls, and there was no age-related change in Langerhans' cell density. These results indicate that patients who develop actinic keratosis or multiple basal cell carcinomas do not differ in Langerhans' cell density from healthy controls and that cumulative sunlight or PUVA exposure does not lead to a persistent reduction in Langerhans' cell numbers.