Keywords: low-dose irradiation, lymphocyte differentiation antigens, DNA, radiation, immunity, low doses, radiation workers, Chernobyl
Immune cells in Chernobyl radiation workers exposed to low dose irradiation
Immune response parameters were studied in Chernobyl radiation emergency workers exposed to low-dose irradiation during 1986–1989 and nuclear industry workers exposed under professional limits. Analysis was performed in irradiation dose limits of 250 and 100 mSv. The comparison group included participants of the clinical–epidemiological registry (n – 42,000) studied in the same time periods. The initial response stage to the radiation exposure was characterised by immunological deficiency with T-cell subset changes. Lymphocyte membrane changes and increased lipid peroxidation were demonstrated due to free radical formation as well as elevated neutrophil peroxidase and catalase activities. In the reconstitution period, inhibition of the immune function was associated with lymphocyte subset changes such as decreased CD3+ and CD4+ cells counts and increased number of somatic mutations in TCR-locus. Changes of the antioxidant defence enzymes, cholesterol content increase and the activation of the processes of lipid peroxidation were also characteristic for this period. Late period after the acute radiation exposure in Chernobyl radiation emergency workers is characterised by decreased CD8+ suppressor cell function that could lead to poor proliferation control. Radiation-exposed over 0.5 Gy are also the risk group for leukaemia development that is characterised by unlimited clonal proliferation. The role of association of elevated content of the metabolite of arachidonic acid 12-HETE as well as other eicosanoids (5-HETE, 15-HETE) produced by the activated platelets, low T-suppressors and NK-cell counts in the promotion of malignant proliferation reactions have to be estimated with the comparative analysis of oncogene expression and the role of apoptosis. No dependencies of dose–effect type were detected in nuclear industry workers. Different types of interdependencies between the immune function and arachidonic acid metabolite 12-HETE are shown with the threshold values of 0.25–0.3 Gy. Lymphocyte reactions are assumed to be of adaptive origin.