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.