title: Ultraviolet a augments solar-simulated ultraviolet radiation-induced local suppression of recall responses in humans.
abstract: Many studies support the role of ultraviolet B in sunlight-induced alteration of the cutaneous immune system. The role of ultraviolet A is less clear, particularly in humans. The aim of this study was to determine the effect of additional ultraviolet A on solar-simulated ultraviolet-induced suppression of recall responses to nickel in humans. Immuno suppression dose-responses were induced in volunteers by exposure to solar-simulated ultraviolet radiation for four consecutive days. The ultraviolet A radiation dose was increased daily by providing additional high-dose ultraviolet A either before, or after the solar-simulated ultraviolet radiation. These ultraviolet A doses can be readily achieved through a sunscreen. Two different ultraviolet A spectra were used; 320-400 nm and 330-400 nm. Ultraviolet A alone did not cause significant immunosuppression, but augmented solar-simulated ultraviolet radiation-induced immunosuppression. Additional ultraviolet A reduced the minimum dose of solar-simulated ultraviolet radiation that was immunosuppressive. Both ultraviolet A spectra had this effect, although photoaugmentation was less pronounced with the 330-400 nm spectrum. Ultraviolet A-induced immediate pigment darkening did not protect from solar-simulated ultraviolet radiation-induced immuno suppression.
authors.affiliation: The Melanoma and Skin Cancer Research Institute and The Department of Medicine (Dermatology), The University of Sydney at Royal Prince Alfred Hospital, Sydney, New South Wales, Australia. jkuchel@med.usyd.edu.au
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Kuchel
authors.forename: Ross St C
authors.initials: RS
authors.lastname: Barnetson
authors.forename: Gary M
authors.initials: GM
authors.lastname: Halliday
mesh_terms: D000328:Adult; D004890:Erythema; D005260:Female; D006801:Humans; D007107:Immune System / Q000528:radiation effects*; D007156:Immunologic Memory / Q000528:radiation effects*; D007165:Immunosuppression Therapy; D008297:Male; D009532:Nickel / Q000276:immunology; D012867:Skin / Q000528:radiation effects*; D012880:Skin Pigmentation / Q000528:radiation effects; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D009532:Nickel