EFFECT OF LOW-DOSE UVB IRRADIATION ON THE MIGRATORY PROPERTIES AND FUNCTIONAL CAPACITIES OF HUMAN SKIN DENDRITIC CELLS

We recently described the 'spontaneous' migration of skin dendritic ce lls out of human split skin during culture. Since newly infiltrating c ells from the circulation are excluded, this in vitro model is very su itable for studying the effect of UVB irradiation on the migratory pro perties, phenotype and functional capacities of skin cells. In the pre sent study, we show that UVB irradiation of the skin before the cultur e period results in a significantly lower number of migrated cells tha t could be obtained compared with untreated skin. Relatively more dend ritic cells of the population that migrated from UVB-irradiated skin w ere of dermal origin, as indicated by a higher percentage of GD1b(+) c ells. These data imply that UVB irradiation inhibits migration, especi ally of the epidermal Langerhans cells. Ultrastructural analysis of th e irradiated skin revealed that the UVB dose used did not cause any di rectly visible damage to the cells. However, the cell population that had migrated from UVB-irradiated skin showed a significantly lower cap acity to stimulate allogeneic T cells. This was not due to a lower exp ression of MHC class II on these cells. The percentage of cells expres sing B7.1, B7.2 and LFA-3 was decreased in the population migrated fro m irradiated skin. The possible mechanism underlying the UVB-induced s uppression is discussed.