title: Trans-urocanic acid, a natural epidermal constituent, inhibits human natural killer cell activity in vitro.
abstract: UV irradiation has been reported to influence NK cell function both in vitro and in vivo. Since urocanic acid may mediate UV-induced immune modulation we tested the effect of trans- and cis-urocanic acid (UCA) on the cytotoxic activity of human peripheral blood lymphocytes against the erythroleukemic target cell line K562 in vitro. Trans-UCA was found to be a strong inhibitor of NK cell activity whereas cis-UCA had no effect. Trans-UCA also partially inhibited cytotoxic function of IL-2-activated NK cells and reduced IL-2-induced activation of NK cells. This is the first report describing trans-UCA to be active, and cis-UCA inactive, in regulating an immune function. In the skin, a decrease in epidermal trans-urocanic acid concentration by UV radiation could produce a favorable milieu for NK cell activity, and thus counteract the impairment of antigen-specific immune surveillance, induced by increased cis-urocanic acid concentrations.
authors.affiliation: Department of Medical Microbiology, University of Turku, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Uksila
authors.forename: J K
authors.initials: JK
authors.lastname: Laihia
authors.forename: C T
authors.initials: CT
authors.lastname: Jansén
mesh_terms: D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D004817:Epidermis / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology; D008214:Lymphocytes / Q000166:cytology / Q000502:physiology; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D014560:Urocanic Acid / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D007376:Interleukin-2; D000242:Cyclic AMP; D014560:Urocanic Acid