The effect of 8-methoxypsoralen and long-wave ultraviolet light on Langerhans cell.

The effect of 8-methoxypsoralen plus long-wave ultraviolet light (PUVA) on Langerhans cell was examined in guinea pigs using ATPase staining method. The number of ATPase-positive Langerhans cells gradually decreased until 5 to 7 days after PUVA treatment, when it was found to be less than 10% to 20% of the original density. Even the ATPase-positive cells exhibited abnormal appearance. The dendritic processes were shortened or disappeared and the central body became oval or round. These changes in population and morphology of Langerhans cell almost returned to normal by 14 days. The inhibitory effect of PUVA on the induction of contact hypersensitivity may be partly due to the alterations of Langerhans cells. Furthermore, the damage on the antigen-presenting cells may accelerate the development of PUVA-induced tumors.