LOW-DOSE ULTRAVIOLET-B IRRADIATION DEPLETES HUMAN EPIDERMAL LANGERHANS CELLS

We have examined the effects of low-dose monochromatic UVB irradiation (295 +/- 5 nm), biologically equivalent to that generally incident on the skin during a 12-session sun-bed course, on the expression of the CD1a epidermal Langerhans cell surface marker in human skin in vivo. In five subjects, 1.5 minimal erythema doses (MEDs) at 29 5 nm deplete d its expression by 50%. In five further subjects, a single 1.5 MED do se, 1.5 MEDs in 10 equal fractions on alternate days, and a single 1.5 MED dose at one-tenth the previously used irradiance, delivered to se parate sites, also led to variable but significant depletion of CD1a e xpression of around 30-50%. Thus, low-dose UVB irradiation, whether re ceived rapidly or slowly, appears significantly and approximately equa lly to deplete human epidermal Langerhans cell numbers as measured by CD1a expression.