Inactivation of antigen receptor genes in mature T lymphocytes, (2)

A flow cytometric method has recently been developed for determining mutant cell (CD3-4+) frequency in T-cell antigen receptor (TCR) genes. Using this method, CD3-4+ frequency was determined in the following five groups: (1) A-bomb survivors exposed to an estimated dose of 0.005 Gy (the control group), (2) A-bomb survivors exposed to 1.5 Gy or more (the exposed group), (3) patients having the retention of thorotrast (the thorotrast group), (4) patients treated with I-131 administration for thyroid cancer (the I-131 treated group), and (5) patients given chemotherapy for lung or breast cancer (the drug treated group). A mean CD3-4+ frequency was 2.73±1.30 x 10-4 for the control group, 3.52±2.72 x 10-4 for the exposed group, 10.6±14.4 x 10-4 for the thorotrast group, 5.18±2.14 x 10-4 for the I-131 treated group, and 4.87±1.92 x 10-4 for the drug treated group. Compared with the control group, all of the other groups had a significant increase in mutant cell frequency. For the I-131 treated group, there was a significant linear correlation between the total dose of I-131 and mutant cell frequency. (N.K.)