DESPITE THE PRESENCE OF UVB-INDUCED DNA-DAMAGE, HLA-DR-VIVO UVB-EXPOSED HUMAN SKIN ARE ABLE TO MIGRATE AND SHOW NO IMPAIRED ALLOSTIMULATORYCAPACITY( CELLS FROM EX)

In this study, we investigated the effect of ultraviolet B radiation o n human Langerhans cell function, Normal human skin was irradiated ex vivo with single doses of ultraviolet B, For assessment of T-cell stim ulatory function, cells that spontaneously migrated from epidermal she ets were used, whereas full-thickness skin biopsies were used to inves tigate alterations in migratory properties. The cells migrating from u ltraviolet B-exposed epidermal sheets demonstrated a decrease in the p ercentage of HLA-DR positive Langerhans cells, as well as a reduced ca pacity to induce proliferation of allogeneic T cells, when compared wi th cells migrating from nonexposed sheets, When a correction was made for the decreased number of HLA-DR positive Langerhans cells migrating from ultraviolet B-exposed epidermis, however, it appeared that the c apacity to induce T-cell proliferation was identical for Langerhans ce lls migrating from ultraviolet B-exposed and nonexposed epidermis. The presence of ultraviolet B-induced DNA damage could be demonstrated in the Langerhans cells from ultraviolet B-treated skin, indicating that the cells had received significant doses of ultraviolet B, As regards the effect of ultraviolet B on migratory properties of Langerhans cel ls, we found not only that reduced numbers of CD1a-positive Langerhans cells migrated from the ultraviolet B-exposed full-thickness skin, bu t also that there was a reduction in CD1a-positive Langerhans cells in the epidermis, This implies that ultraviolet B induces death of Lange rhans cells as well as loss of cell surface molecules rather than alte ring Langerhans cells migration, whereas the Langerhans cells that wer e still able to migrate fully retained the capacity to activate alloge neic T cells.