Quantitative detection of apoptotic thymocytes in low-dose X-irradiated mice by an anti-single-stranded DNA antibody

The quantitative detection of apoptotic cells in low frequency in the thymu s of mice irradiated with X-rays using an anti-single-stranded DNA antibody was explored. The antibody against single-stranded DNA (anti-ssDNA) was ob tained with rabbits hyperimmunized with complexes of alkaline-denatured cal f thymus DNA. AKR female mice were irradiated with 10 to 100 cGy or 4 Gy X- rays; thereafter, thymus sections were prepared at various times after irra diation. The detection and counting of apoptotic cells in the section were performed after histochemical staining using an anti-ssDNA antibody. The re sults demonstrate that, although sensitive and quantitative detection of ap optotic cells in irradiated thymus using the anti-ssDNA antibody is possibl e, the sensitivity is lower compared to that of in situ endlabeling methods , such as TUNEL or ISEL. The antibodies could also be used for rat thymus a nd spleen. In addition, an increase in positively stained cells by both met hods was detected as early as 6 min after the irradiation of mice.