Recovery Process of Langerhans Cells in Human Skin Following Ultraviolet B Irradiation

Abstract

Ultraviolet B (UVB) irradiation has been shown to diminish the local density of epidermal Langerhans cells in both animals and humans. The methods employed for these studies have varied widely. Variables include the UVB source and dosage, skin preparations such as epidermal sheets or cell suspensions, and the Langerhans cell markers used for enumeration. However, although the immediate adverse effects of UVB irradiation are well documented, information on the recovery time of Langerhans cells in human skin is not readily available.Human volunteer subjects were irradiated with approximately 2 minimal erythema doses (MEDs) of ultraviolet light from a xenon compact arc solar simulator at time periods of 1, 7, 14, 21, 28, and 35 days before biopsy. Langerhans cells were enumerated using epidermal sheets stained for HLA-DR and CD la markers and were also morphologically evaluated. At 24 hr after irradiation, the number of Langerhans cells was markedly decreased to approximately 60% of normal and their morphology severely altered. These changes were observed after 7 days but showed recovery at 2 weeks after irradiation. After 4-5 weeks after irradiation, the number of Langerhans cells in irradiated sites was back to its normal level.