MUTANT FREQUENCY AT THE HPRT LOCUS IN PERIPHERAL-BLOOD T-LYMPHOCYTES OF ATOMIC-BOMB SURVIVORS

The mutant frequency at the hypoxanthine-guanine phosphoribosyltransfe rase locus in peripheral blood lymphocytes was measured for 254 atomic bomb survivors (171 exposed and 83 control survivors) by a colony ass ay using recombinant human interleukin-2. Weak but significant effects were detected for atomic bomb radiation dose and smoking status at th e time of examination but not for age and sex. However, the slope of t he dose-response curve is quite small, and the smoking effect would no t have been significant without the inclusion of data from just three individuals with extremely high mutant frequencies. The weakness of th e dose response is at least partly due to the time lapse of 50 years s ince radiation exposure. Among the 254 survivors, 23 had chromosome ab erration data in lymphocytes and the dose response was highly signific ant. However, the correlation between the mutant frequency and the pro portion of cells with aberrations was not significant. It was conclude d that the lymphocyte mutation assay is presently not sensitive enough for biological dosimetry of radiation exposure in the survivors.