COMPARATIVE IMMUNOTOXICOLOGY OF ULTRAVIOLET-B EXPOSURE - I - EFFECTS OF IN-VITRO AND IN-SITU ULTRAVIOLET-B EXPOSURE ON THE FUNCTIONAL-ACTIVITY AND MORPHOLOGY OF LANGERHANS CELLS IN THE SKIN OF DIFFERENT SPECIES

Ultraviolet (UV) a-induced morphological and functional changes in the skin of mice, rats and humans were investigated Changes in the morpho logical structure of Langerhans cells (LC), the major antigen-presenti ng cells in the skin, using confocal laser scanning microscopy, were f ound in mouse and rat skin after in situ exposure to high doses of UVB radiation (FS40) (3-9 kJ/m(2)). Similar UVB doses failed to induce al terations in the morphological structure of human LC. Alterations in t he function of epidermal cells (especially LC) were studied, using the mixed skin lymphocyte response (MSLR). In vitro WE exposure of epider mal cells (EC), derived from the skin of the different species, reveal ed that low doses of UVB radiation impaired the stimulatory capacity o f these cells dose-dependently; mouse epidermal cells were most UVB-su sceptible, while human cells were least UVB susceptible. For suppressi on of the stimulatory capacity of EC after in situ UVB exposure of ski n tissue, higher doses of UVB radiation than the in vitro UVB exposure were needed in all species tested. Also in this in situ set-up mouse epidermal cells were most UVB-susceptible, and human epidermal cells w ere least UVB-susceptible. The magnitude of differences in susceptibil ity for UVB-induced changes in the stimulatory capacity of EC after in situ and after in vitro exposure experiments was similar. Firstly, it may be concluded that UVB impairs the functional activity of LC at a lower dose than that which alters the morphology of these cells. Secon dly it is clear that epidermal cells, especially LC, from the skin of rodents are more susceptible to UVB than epidermal cells derived from human skin. It is important to account for these differences in suscep tibility when data on the effects of UVB radiation on the immune syste m in rodents are extrapolated to humans.