Immunological detection of thymidine photoproduct formation in vivo.

Rabbits immunized with ultraviolet (UV)-irradiated DNA which was complexed to methylated bovine serum albumin as carrier responded by making high titers of antibodies. These were mainly 7S antibodies and reacted only with UV-irradiated DNA, showing no cross reactions with unirradiated native or heat-denatured single-stranded DNA. The reactions were demonstrated in immunofluorescence by showing that rabbit antisera reacted with nuclei of UV-irradiated tissue sections but not with unirradiated tissue nuclei. In complement fixation, antisera reacted only with irradiated purified DNA. Specific antigenic determinants on UV-irradiated DNA were determined by inhibition of immunofluorescence and complement fixation using irradiated thymine and cytosine and the respective nucleosides and nucleotides as inhibitors. Cytosine photoproducts were not inhibitory but thymine photoproducts were partially inhibitory. Irradiated polycytidylic acid was also not inhibitory but irradiated polydeoxythymidylic acid gave complete...