In vivo PUVA and UVB sensitivity of various human epidermal Langerhans cell markers (ATPase, HLA-DR and T6)--dose-response and time-sequence studies.

Abstract

To form a comprehensive view of the UV‐sensitivity of human epidermal Langerhans cells (LC), the time‐sequence and close response effects of single doses of UVB or 8‐methoxypsoralen plus UVA (PUVA) radiation on three different LC surface markers were studied with histochemical and immunohistochemical staining. An increasing PUVA dose from 1 to 10 J/cm2 caused an almost linear decrease in the surface enzyme (ATPase) positive LC count, whereas the cell surface antigens (HLA‐DR and T6) were rather more resistant, up to a PUVA dose of 5 J/cm2. A single dose of 5 J/cm2 of PUVA induced an LC depletion that was similar during the 21 days of observation, irrespective of whether the cells were visualized with ATPase staining or with monoclonal antibodies against the cell surface antigens HLA‐DR or T6. In each case, the nadir was reached 14 days after irradiation; the average residual LC count was then 57%. The cell counts 21 days after PUVA irradiation were still only approximately 74% of the nontreated skin counts. Langerhans cell depletion induced by an erythemagenic dose of UVB irradiation was swifter and more pronounced than that induced by 5 J/cm2 of PUVA but, again, a similar time schedule was recorded with ATPase, HLA‐DR and T6 staining.