Immune serum against anti-DNA-8-methoxypsoralen photoadduct.

Specific immune serum against photo-damaged DNA with the photoadducts of 8-methoxypsoralen (8-MOP) was obtained. The antigenic determinant is a polynucleotide chain with a mono-photoadduct: a coumarin moiety of psoralen linked through a cyclobutane ring to the 5,6-bond of thymine. The specific rabbit antiserum was used in the immunofluorescence method, for the detection of photodamaged DNA in the kinetoplasts and nuclei of unicellular organisms Crithidia luciliae, in the nuclei of snap-frozen tissue of mammals, and in human blood lymphocytes. Detection by the immunofluorescence method was limited by psoralen availability in situ; the psoralen concentration should be in the range 0.05-0.2 microgram/cm2 on specimens submitted to a topical application or about 1 microgram/ml in cell suspension. The long-wave ultraviolet light (UV-A) exposure dose applied to the nuclei should exceed 1 J/cm2.