The participation of oxygen in the process of the interphase death of T-lymphocytes following irradiation in vivo

The ability of lymphocytes to inhibit proliferation of non-syngeneic stem cells decreases differently after exposure in vivo and in vitro. The causes of the observed differences and the mechanism of radiation impairment of this function under different irradiation conditions have been investigated. Cells exposed in vivo die in the interphase irreversibly. The newly formed lymphocytes start the repair process as late as one month after irradiation. The injury to in vivo exposed cells is severer due to the presence of oxygen in tissues. A definite time interval is needed for the damaging effect of oxygen radicals to be implemented: the effect is maximum as early as 4 h following irradiation. With in vivo exposure under hypoxic conditions the functional activity of lymphocytes is the same as that of lymphocytes irradiated in vitro with the same dose. In vitro irradiation of lymphocytes at a high oxygen content causes a decrease in the functional activity of cells.