UVB RADIATION PREFERENTIALLY INDUCES RECRUITMENT OF MEMORY CD4(-CELLSIN NORMAL HUMAN SKIN - LONG-TERM EFFECT AFTER A SINGLE EXPOSURE() T)

Acute, low-doses of ultraviolet (UV)-B radiation affect the immune com petent cells of the skin immune system. In this study, we examined the time-dependent changes of the cutaneous T cell population in normal h uman volunteers following a single local exposure to UV, Solar-simulat ed UV radiation caused an initial decrease in intraepidermal T cell nu mbers, even leading to T cell depletion at day 4, whereupon a consider able infiltration of T cells in the epidermis occurred that peaked at day 14. In the dermis the number of T cells was markedly increased at days 2 (peak) and 4 after irradiation, and subsequently declined to th e nonirradiated control values at day 10. Double-staining with several T cell markers showed that the T cells, infiltrating the (epi)dermis upon UV exposure, were almost exclusively CD4(+) CD45RO(+) T cells, ex pressing an alpha/beta type T cell receptor, but lacking the activatio n markers HLA-DR, VLA-1, and IL-2R, Application of UVB radiation resul ted in similar dynamics of T cells, indicating that the WB wavelengths within the solar-simulated UV radiation were responsible for the sele ctive influx of CD4(+) T cells. In conjunction with UVB-induced altera tions in the type and function of antigen-presenting cells (i.e., Lang erhans cells and macrophages), the changes of the cutaneous T cell pop ulation may also contribute to UVB-induced immunosuppression at skin l evel in man.