The suppression of contact hypersensitivity by UVB (280–320 nm) radiation can be prevented by photoreactivating light (PRL; 320–400 nm) in the opossum Monodelphis domestica, implicating epidermal DNA lesions as the immunosup-pressive impairment. However, contact hypersensitivity can also be suppressed in the opossum with exogenous cis-urocanic acid, a molecule which is produced in UVB-irradiated epidermis and is a second potential mediator of photo-immunosuppression apparently independent of UVB-induced DNA damage. Here we demonstrate that irradiation of opossums with PRL either before or following treatment with exogenous cis-urocanic acid, significantly reduced the degree of immunosuppression. This suggests that, in addition to its capacity to initiate post-UVB-exposure epidermal DNA repair, the PRL waveband can induce an immunoprotective product, as yet unidentified, in opossum epidermis.

Keywords:
Contact hypersensitivity, Urocanic acid, Monodelphis domestica, Photoreactivating light, UVA radiation, Immunosuppression
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© 1997 S. Karger AG, Basel
1997
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