title: Wavelength dependency for UVA-induced suppression of recall immunity in humans.
abstract: BACKGROUND
  Ultraviolet (UV) A radiation, which has both mutagenic and immune suppressive effects on the skin, is increasingly recognised as a key contributor to cutaneous carcinogenesis. Whilst short wavelength UVB (290-320 nm) is well-recognised as an environmental health hazard, the dangers of UVA (320-400 nm) are relatively unexplored.
  
  
  OBJECTIVE
  Using the nickel model of recall immunity in healthy human volunteers, we determined the wavelength dependency for UV-induced immunosuppression across the UVA spectrum.
  
  
  METHODS
  Dose-response curves were established for local suppression of contact hypersensitivity responses to nickel at 7 wavelengths between 331 and 392 nm.
  
  
  RESULTS
  We found a broad peak of UVA immune suppressive effectiveness at 364-385 nm. Whilst we had previously found linear dose-responses for UVB-induced immunosuppression in this model, long wavelength UVA caused bell-shaped, Gaussian dose-responses, suggesting different chromophores and mechanisms of immunosuppression for UVB and UVA.
  
  
  CONCLUSIONS
  The immunosuppressive peak induced by longwave UVA has not been described previously for any species and being close to the border with visible light indicates an unexpected role for these long wavebands in human health and disease.
authors.affiliation: Discipline of Dermatology, Bosch Institute, The University of Sydney at Royal Prince Alfred Hospital, Camperdown, Sydney, NSW 2050, Australia.
authors.forename: Yasmin J
authors.initials: YJ
authors.lastname: Matthews
authors.forename: Gary M
authors.initials: GM
authors.lastname: Halliday
authors.forename: Tai A
authors.initials: TA
authors.lastname: Phan
authors.forename: Diona L
authors.initials: DL
authors.lastname: Damian
mesh_terms: D000328:Adult; D017449:Dermatitis, Allergic Contact / Q000209:etiology / Q000276:immunology / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007108:Immune Tolerance / Q000528:radiation effects*; D007165:Immunosuppression Therapy; D008875:Middle Aged; D009532:Nickel / Q000633:toxicity*; D012867:Skin / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D009532:Nickel