Radiation-induced changes in the immune system develop quite early after the onset of radiation exposure and persist over a long time after it's removal. In case of chronic radiation exposure at dose rate lower than 0.1 Gy/year, the threshold of annual dose to suppress red bone marrow hemato- and immunopoiesis reaches 0.3-0.5 Gy. It was shown that adaptation mechanisms are triggered under the chronic impact of ionizing radiation in the hematopoietic system. In our study we quantitatively and qualitatively analyzed relationships between individual arms of the immune system which is important for understanding features of homeostasis and the adaptation capacity of immune system in chronically irradiated subjects at later time points. The main group included 376 persons exposed to chronic irradiation due to 1949-1960 industrial pollution with radioactive waste residing in Techa River basin. Average radiation dose for the red bone marrow in this group was 1.08±0.04 (0.08-4.46) Gy. The comparison group included 162 unexposed persons. The mean age of people in the main and comparison group was 70.3±0.3 (58-88) and 69.3±0.5 (58-90) years, respectively. The Kendall correlation analysis identified 82 statistically significant correlations (correlation coefficient higher than 0.3, p 0.05) between individual immune parameters versus 65 similar correlations found in the comparison group. The majority of identified correlation links in both groups ranged from 0.3 to 0.5 (main group – 57 correlations, comparison group – 41 correlations). There were found 16 and 14 correlations in the main and comparison group, respectively, with a coefficient ranged from 0.5 to 0.7. The correlation coefficient value higher than 0.7 was noted for 9 correlations in the main group and for 10 – in the comparison group. The χ-square analysis revealed no significant differences between total number of correlations and number of correlations of varying strength both in the main and comparison groups. The obtained data are consistent with previous studies and confirm that delayed changes in the immune system of subjects exposed to chronic low-rate irradiation were mild and evidenced about developed feedforward and feedback compensatory mechanisms.

Persons exposed to ionizing radiation in utero and in early childhood constitute a risk group for the development of long-term stochastic consequences of irradiation. The imbalance of cytokines at the long terms after irradiation could be considered a carcinogenic triggering factor in subjects previously irradiated in utero and in early childhood, thus determining relevance of the study. The aim of the present study was to assess the levels of serum cytokines in native residents of coastal villages at the Techa River, whose chronic irradiation had been begun antenatally and to study probable interrelatirons between the detected changes, radiation and non-radiation factors at long terms after the exposure was begun. The main group included 61 persons from the Techa River Cohort who were born in 1950-1960, whose irradiation was begun in utero, being continued over the early postnatal period. For patients from the main group, the mean dose of antenatal radiation was calculated 74.7 mGy for red bone marrow as of, the mean dose of postnatal irradiation was calculated for red bone marrow as 537.5 mGy, and the median age of patients was 64.0 years. The comparison group (90 nonirradiated persons) was comparable to the main group in terms of age, gender, ethnicity and socio-economic status. The median levels for IL-2 in the main group were 1.37 pg/ml; in the comparison group, 2.70 pg/ml, p = 0.020; for IL-10, 4.53 pg/ml versus 7.58 pg/ml, p = 0.030 respectively; for GM-CSF, 0.39 pg/ml in the subjects who were irradiated in utero and in the early postnatal period versus 0.86 pg/ml in non-irradiated persons, p = 0.040. The median serum concentrations of IL-1β, IL-1α, IL-1(ra), IL-4, IL-6, IL-8, G-CSF, TNFα, IFNα, IFNγ in the study group did not show differences from the values in a group of non-irradiated persons. The decrease of the serum IL-2, IL-10 and GM-CSF levels in the persons of the main group did not depend on the dose of antenatal irradiation to red bone marrow, and on the radiation dose to red bone marrow received during the postnatal period of ontogenesis. In the main group, there was a moderate inverse relationship between the serum IL-10 level and age at the time of examination (SR = -0.53, p 0.001). Serum concentrations of IL-2 and IL-10 in the people from comparison group showed a moderate positive correlation with their present age (SR = 0.47, p 0.001 and SR = 0.42, p 0.001 respectively).

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