Effect of UVA and UVB irradiation on human epidermal Langerhans cell membrane markers defined by ATPase activity and monoclonal antibodies (OKT 6 and anti-Ia).

Healthy human volunteers were irradiated with graded doses of UVA and UVB radiation on the volar aspect of their forearms. The UVA doses ranged from 8 to 100 J/cm2, and the UVB doses from 37 to 416 mJ/cm2, corresponding to 5 to 52 mJ/cm2 of erythemally effective (300 nm) radiation (1/4-3 X MED). 7 days after irradiation, punch biopsy specimens were obtained from UVA and UVB irradiated spots. Epidermal sheets were stained for Langerhans cells (LC) using 3 different histochemical methods, viz: ATPase activity and immunoperoxidase staining with monoclonal antibodies against T6 and Ia antigens. A slightly higher control LC count was obtained with anti-T6 staining (848 cells/mm2) than with anti-Ia or ATPase staining (728 and 721 cells/mm2 respectively). No significant change in LC count was detected with any of the staining methods after UVA doses of up to 100 J/cm2. In contrast, UVB irradiation caused a dose-dependent decrease in the LC counts. The decrease was quite similar whether measured by anti-T6 or anti-Ia staining. With ATPase staining, the decrease in LC numbers was somewhat more pronounced at low to medium UVB doses, but at the dose of 416 mJ/cm2 (52 mJ of erythemally effective UVB, corresponding to approx. 3 X MED), the residual LC count as determined with any of the 3 histochemical methods was within the range of 23-30% of the control LC count. We conclude that the activity of the membrane-bound enzyme, ATPase, is more sensitive to abrogation by moderate UVB doses than the immunological reactivity of the 2 surface antigens, T6 and Ia.