Measurement of the CD3^-4⁺ variant T cell frequency by flow cytometry after X-irradiation on mice

Variant cell frequency of mice T-lymphocytes defective in the T-cell receptor (TCR) gene expression was measured by flow cytometry. Splenic T-lymphocytes were obtained from mice after irradiation and stained with fluorescein-labeled anti-L 3 T 4 (CD 4) and phycoerythrin-labeled anti-CD3-ε antibodies. They were analyzed with a flow cytometer to detect variant T cells lacking surface expression of TCR/CD 3 complexes which showed CD3^-4⁺ T cells. Variant T cells could be observed 3 days after 3 Gy irradiation. Frequency of variant T cells increased to the maximum level of 94×10^-4 between 15 and 21 days after 3 Gy irradiation on BALB/c mice and gradually decreased with a half-life of approximately 17 days. We examined the strain difference in radiosensitivity of splenic T-lymphocytes in BALB/c, C57BL/6, C3H/ He and B6C3F₁ mouse strains by this assay method. We observed that BALB/c showed the most radiosensitivity. This assay method is quick and easy in comparison with other methods and is considered useful for the mutagenicity test.