Frequency of mutant T lymphocytes defective in the expression of the T-cell antigen receptor gene among radiation-exposed people

The frequency of mutant T lymphocytes defective in T-cell receptor gene (α or β) expression was measured using the two-color flow cytometric technique. Results for a total of 203 atomic bomb survivors, 78 of whom were proximally exposed (DS86 doses of ≥ 1.5 Gy) and 125 of whom were distally exposed (DS86 doses of < 0.005 Gy), showed that the mutant frequency was significantly higher in males than in females. No significant dose effects were observed. In contrast, a significant increase of mutant frequency was observed for six patients treated with Thorotrast, a contrast medium containing 228Th formerly used for radiodiagnosis. In addition, thyroid disease patients treated with 131I showed a dose-related increase of mutant frequency. It was suggested that the present T-cell receptor mutation assay has a unique characteristic as a biological dosimeter for the measurement of recent exposures to genotoxic agents. (author)