An epidemiological analysis of monitoring of the immune status of chernobyl nuclear accident liquidators for early detection of risk groups and diagnosis of cancer diseases. Communication 2. Dependence of the rate and changes in the immune status on radiation accident risk factors

Abstract

It was demonstrated that malignant neoplasms (MNs) most frequently develop in the liquidators involved in the cleanup activities after the Chernobyl nuclear accident (ChNA) in 1986 (43.75%) and the liquidators involved in long-term activities, one-quarter of whom also participated in the cleanup in 1986. The specific features of the immune status (IS) depending on the period and year of the cleanup activities in the ChNA area were determined. In the cohort with a confirmed MN diagnosis, the observed deviations in the people who participated in these activities only in 1986 and on a permanent basis, including 1986, coincided in their pattern but differed in the magnitude of changes in immunological characteristics. Long-term participation during the extreme period and, correspondingly, higher exposure caused an increase in the contents of CD8+ T cells, CD16+ lymphocytes, and activated T lymphocytes, as well as decreases in the total immunoregulatory index, percentage of CD3-16/56+ (NK), and total IgE and a more pronounced deficiency in B lymphocytes. Differences between the groups of liquidators who participated in the cleanup activities in 1986 and 1987 were detected. The liquidators-1987 display the most pronounced deviations in the IS characteristics. Permanent presence in the ChNA area in 1986 and 1987 caused a similar effect but the magnitude of changes in the content of CD4+ T lymphocytes (↓), content of CD8+ T lymphocytes (↑), and immunoregulatory index (↓) was considerably higher in liquidators-1987. The permanent cleanup activities in Chernobyl in 1987 caused a deficiency in CD4+ T lymphocytes; more pronounced increase in the content of CD8+ T lymphocytes; decrease in CD4+/CD8+ index; change in the ratio of NK-T to NK cells; elevation in the counts of CD95+, HLA-DR+, and activated T lymphocytes; and decrease in the level of total IgE. Any increase in the expression of cell activation markers was undetectable in the liquidators-1986 involved in the cleanup activities on a long-term basis. The specific features of the IS changes depending on the dose of external γ-irradiation were determined. It was shown that the MN rate in liquidators increases with age relative to the number of examined people in each age cohort. The differences in the IS age-related dynamics in liquidators with and without MNs were detectable in stable contents of CD3+, CD4+, and CD8+ T lymphocytes; immunoregulatory index; and contents of CD95+ cells and serum IgA at ages of 40 to 70 years old with a subsequent decrease in these parameters and elevation in the content of CD8+ T lymphocytes with age in the absence of MNs; continuous increase in CD3-16/56+ (NK) cells in the presence of MNs; and decreases in these values after 70 years in the absence of MNs. In both groups of liquidators older than 70 years (with and without MNs), a deficiency in the T-cell component (CD3+ and CD4+ T lymphocytes and CD4+/CD8+ ratio) and an increase in the counts of CD8+ T lymphocytes are characteristic of the IS. A growing deficiency in CD4+ T lymphocytes during the monitoring on the background of increasing content of CD8+ T lymphocytes, which additionally contributes to the weakening of immune regulation due to progressing abnormalities in the ratio of regulatory T-lymphocyte subpopulations, can be regarded as one of the characteristics that suggest an adverse life expectancy prognosis for people with MNs.