Mechanism of radiation-induced apoptosis of human peripheral T cells

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The mechanism leading to the high level of radiosensitivity of T lymphocytes has not yet been fully described. In our previous study, we demonstrated that human peripheral T lymphocytes revealed early apoptotic changes (annexin-V-positive) and late apoptotic changes (propidium iodide-positive), at 13 and 24 h after irradiation of 5 Gy, respectively. Changes in mitochondrial membrane potential were observed at 10 h after irradiation of 5 Gy. Mitochondrial cytochrome c release was confirmed following the changes in mitochondrial membrane potential. In order to elucidate the mechanism which occurs prior to the mitochondrial membrane potential changes, we examined the radiation dose and the timing of oxidative DNA damage induced in human peripheral T lymphocytes following 10 MV X-ray irradiation. As a result, the production of 8-oxoguanine, i. e., the product of oxidative DNA damage, was clearly identified starting at 10, 6, and 3 h, after 2, 5, and 20 Gy of irradiation, respectively.