Detection of single-strand breaks and base damage in DNA of human white blood cells as a tool for biological dosimetry of exposure to ionizing radiation

An immunochemical assay has been adapted to detect DNA damage in whole blood at biologically relevant doses of ionizing radiation. Upon alkaline treatment of whole blood, both strand breaks and base damage (which is converted into strand breaks by the addition of damage-specific enzymes) are detected by using antibodies that specifically bind to single-strand DNA. Single-strand breaks can be detected immediately after irradiation at doses as low as 0.2 Gy. With unknown background damage, the lower detection limit increased to approximately 0.5 Gy immediately after irradiation due to interindividual variation. Because single-strand breaks are repaired rapidly, this method is suitable only for blood collected less than 1 hour after exposure. Base damage represents a very promising biological indicator that can be used 1 hour and longer (at least to 4 hours) after radiation exposure because of an apparent lack of base damage repair during this time window.