ABSTRACT
We studied the number and morphologic alterations of ATPase-positive Langerhans cells (LCs) in guinea pig epidermal sheets and also performed electron microscopic observations on them following long-term systemic psoralen photochemotherapy (PUVA) using 8-methoxypsoralen (8-MOP) and trimethylpsoralen (TMP). We con-firmed that the LCs are sensitive to PUVA treatment. The LC depleting effects of PUVA are dose-related and the restorator1 of LCs takes place by the 4th week following cessation of PUVA. Neither psoralens alone nor UVA alone showed any effects on LCs. There were no significant differences between 8-MOP and TMP when comparing the effects of 8-MOP plus UVA and TMP plus UVA on LC numbers and morphology. It seems that a moderate dose of PUVA causes an actual decrease in the number due to cell damage. Also, it appears likely that giant LCs appear during and following PUVA treatment as a compensatory process of the remaining cells.