Delayed correlated parameters of adaptive and innate immunity in chronically irradiated subjects

Abstract

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.