Action Spectrum of Ultraviolet Light-Induced Damage to Nuclear Dna In Vivo**From the Department of Experimental Pathology and the Division of Dermatology, Scripps Clinic and Research FoundatiOn, La Jolla, California 92037 and the Department of Pathology, University of Texas, Southwestern Medical School, Dallas, Texas 75235.

Antiserum against UV-irradiated DNA was used as a specific reagent in an indirect immunofluorescent technique to detect photochemically damaged DNA in skin. Hairless mice were irradiated with different wavelengths of monochromatic UV radiation, killed immediately after irradiation and the skin examined for photochemical DNA lesions in cell nuclei with the immunofluorescent technique. UV radiation from 254 to 300 nm was effective in producing photochemically damaged DNA in cell nuclei of the epidermis of irradiated hairless mice. However, at 310 nm approximately four times more radiant energy was required than at the shorter wavelengths to produce photochemically damaged nuclear DNA