Shi YQ Li L Sanal O Tezcan I Emery GC Blattmann H Crompton NE 2001 PURPOSE Cells from ataxia-telangiectasia (A-T) patients are extremely sensitive to radiation but display decreased apoptosis, as measured during the first 3 days following radiation. To explain this apparent contradiction, we examined apoptosis in normal and A-T cells at late time points following radiation, under the assumption that radiation-induced apoptosis is delayed in the A-T cells. METHODS AND MATERIALS Blood cells and lymphoblastoid cell lines from A-T patients, as well as healthy donors, were irradiated with X-rays. Apoptosis was measured at different time points (up to 7 and 30 days for lymphocytes and lymphoblastoid cells, respectively) using a flow cytometric method based on the reduction of intracellular DNA content (sub-G1 population). RESULTS Compared to normal cells, CD4 and CD8 A-T lymphocytes displayed constantly reduced levels of radiation-induced apoptosis for up to 7 days after treatment. A-T lymphoblastoid cells, however, displayed a delayed and prolonged apoptosis. CONCLUSION A-T lymphoblastoid cells show high levels of delayed radiation-induced apoptosis, which may contribute to the high cellular radiosensitivity displayed by the A-T phenotype. ATM (the gene mutated in A-T) plays different roles in the apoptotic response to ionizing radiation in quiescent lymphocytes and proliferative lymphoblastoid cells. https://sonar.ch/global/documents/676 eng info:eu-repo/semantics/altIdentifier/doi/10.1016/s0360-3016(00)01478-4 info:eu-repo/semantics/altIdentifier/pmid/11173154 International journal of radiation oncology, biology, physics. - 2001 Adolescent Adult Aged Apoptosis Ataxia Telangiectasia CD4-Positive T-Lymphocytes CD8-Positive T-Lymphocytes Cell Line Child Child, Preschool Flow Cytometry Humans Middle Aged Radiation Tolerance Time Factors High levels of delayed radiation-induced apoptosis observed in lymphoblastoid cell lines from ataxia-telangiectasia patients. http://purl.org/coar/resource_type/c_6501