Chromosomal radiosensitivity of Down syndrome lymphocytes at different stages of the cell cycle.

Down syndrome (DS) is one of the most common types of congenital anomalies. In addition to a wide spectrum of developmental abnormalities, DS patients are also highly sensitive to the induction of chromosomal aberrations when their GO lymphocytes are exposed to ionizing radiation. We conducted the present study to evaluate the effect of X-rays on proliferating lymphocytes from DS and normal individuals. We found that DS lymphocytes were significantly more sensitive to X-ray induction of chromosome aberrations than normal cells, when they were irradiated at the G0, G1 and S phases of the cell cycle. The S phase was the most radiosensitive phase and would lead to extensive cell killing, whereas the G1 phase seemed to be more prone to the induction of chromosome rearrangements that would potentially lead to serious long-term consequences.