[Remote effects at cell and subcell level in the hemopoietic system after chronic radiation exposure in man].

The parameters characterizing the state of hemopoietic cells obtained from chronically exposed residents of the Techa riverside villages studied at late time after the exposure included: the level of somatic mutations in the TCR gene, the level of chromosome aberrations, the intensity of peripheral blood lymphocyte apoptosis. Exposed versus unexposed subjects (controls) showed an increased frequency of CD3-CD4+ T-lymphocytes, chromosome aberrations of stable type (translocations) and unstable type (dicentrics, rings), and also increased intensity of lymphocyte apoptosis. The findings of tests using a standard additional gamma-irradiation (1 Gy) accompanied by 24-hour incubation indicated that the rate of apoptosis of lymphocytes was significantly higher in exposed individuals in comparison with unexposed ones. It was suggested basing on the obtained data that at late time the chronic (for over 50 years) exposure at RBM doses from 0.01 to 3.22 Sv was a factor inducing the damage to the genetic apparatus of hemopoietic cells. Evidently, the initial chronic low-intensity irradiation in the above-indicated dose range activates adaptive processes at the cellular level in hemopoietic cells. Late time after the onset of exposure the adaptation reserves are depleted in chronically exposed persons which brings about its failure in the case of a challenge by additional external exposures.