The immune system under combined exposure to gamma radiation (dose of 6 Gy, remote period) and emotional stress
Our study showed that combined exposure of experimental animals to a high dose of radiation in the remote period and emotional stress acted as an immunosuppressive agent, revealing the dominant role of ionizing radiation. We noted the occurrence of leukopenia in experimental animals, with their number of leukocytes being reduced by 19.65 % (p < 0.05) (Table 1 ). A significant reduction was shown in the absolute number of lymphocytes in blood from 2,68 ± 0,11 × 109/L to 2,24 ± 017 × 109/L (p < 0.05), whereas their relative number was not markedly changed (р ˃ 0.05).
The related content of CD3+ lymphocytes in experimental rats with an absolute reduction in their number by 48,34 %, p < 0.001), was demonstrated to correspond to that of the intact value. The subpopulation of T-lymphocytes under these conditions exhibited the following changes: the absolute number of CD4+ was decreased by 38,16 % (p<0,01), the elative by 28,9 % (p < 0.05), the absolute number of CD8+ by 33,33 % (p < 0.05), and the relative by 33,24 % (p < 0.05). At the same time, the immunoregulatory index was shown to be accordingly decreased due to a decrease in the number of lymphocytes with helper activity. During this period, we noted a reliable increase in the index of leukocyte migration in the LMIR reaction to PHA from 0.86 ± 0.05 to 1.11 ± 0.09, indicating a decrease in the functional activity of the T-system of immunity (p < 0.05).
Collectively, our results indicated that following the combined effect of remote period sublethal gamma radiation and emotional stress there was a decrease in the total number of lymphocytes; this decrease in some CD3+ and several CD4+ lymphocytes, which appeared to play a considerable role in immunological reactivity, was also reflected in the low indicators of IRI. In addition, we found that in parallel with a decrease in the number of CD8 + lymphocytes, the functional capacity of T-lymphocytes was also decreased.
Our study results showed that under the combined effect, the absolute and relative number of CD19+ lymphocytes in the blood of animals was increased by 20 % and 48.46 %, respectively, compared with the control (p < 0.05). This combination had also a significant impact on the concentrations of CIC. Thus, we observed a 26.12 % decrease (p < 0.05) in the concentration of CIC in the serum of experimental rats. At this background of the increase in the concentration of CD19+ in investigated animals, we identified a suppression in the levels of IgA (14,89 %, р ˃ 0.05) and IgG (on 23,37 %, р < 0.05), whereas the concentration of IgM was shown to be increased to 40,17 % (р < 0.05). Regarding the phagocytic activity of blood cells, we noted a suppression by 23,77 % (p < 0.05) and decrease in the phagocytic number by 12,95 % (р ˃ 0.01).
Moreover, the NTT-test indicator exhibited a downward trend. It should be noted that the implementation of recovery processes in the body is known to be facilitated in the remote period after exposure with a decrease in the dose rate. Under irradiation of the organism with different power, the degree of the response of its reserve adaptive capacity would be different. The revealed changes in the remote period characterizing the immunodepression of the irradiated organism could be considered as an adaptive-compensatory reaction of the organism in response to radiation alone and in combination with nonradiative factors [31].
Thus, in the remote period after the combined exposure to sublethal gamma-irradiation and emotional stress in the early stage of the adaptation syndrome, all cells of the T-system of immunity, such as CD4+/CD8+, as well as the functional ability of leukocytes and mononuclear phagocytic system of the organism decrease. Moreover, we noted a significant depression of immunoglobulins A and G, whereas IgM was shown to be activated. The decrease in the content of IgA and G testified to the occurrence of immunodeficiency, which is known to be accompanied by chronic inflammation and the presence of high tendencies for the development of neoplasm at high doses of ionizing radiation. Based on the results of this study, we could conclude about the dominant role of ionizing radiation in the immunological reactivity of organisms.