Spectral and dose dependence of ultraviolet radiation-induced immunosuppression

Ultraviolet radiation (UV) wavelength and dose dependence has been demonstrated for a number of cutaneous endpoints such as erythema, pigment darkening, DNA damage, and photocarcinogenesis. More recently, a number of in-vitro and in-vivo models of UV immunosuppression have implicated UVA (320-400 nm) in immune protection as well as immune suppression. While the wavelength dependencies for immunosuppression within UVB have been well established in mice, the exact role of specific UVA wavelengths has been less clear. Moreover, in humans, the spectral dependence of UV immunosuppression is even less well established. This review firstly outlines the established UV action spectra for a variety of cutaneous effects. The waveband and dose dependence of UV immunosuppression and its mechanisms are explored with a focus on in-vivo models. Finally, since UV immunosuppression along with DNA damage is thought to play a central role in the development of skin cancer, a clearer understanding of the immunosuppressive potential of discrete UV wavebands will allow a more rational approach to our understanding and prevention of skin cancer.