Sokolenko V. L.

PHYSIOLOGY

Scentific article

Thyroid hormones are able to exert a significant influence on immune system and its functions, both in vitro, and at the level of the whole body. This influence occurs at the level of separate immunocompetent cells, their populations and subpopulations. On the other hand, the presence of receptors to interleukins on thyroid cells provides the influence of immune factors on the functional activity of thyrocytes. Thus, there is a fairly significant interdependence between thyroid and immune systems. We studied the connection between indices of thyroid and immune systems among people who were exposed to Chernobyl accident factors. The level of thyroxine (T4) in blood serum was studied using a test-kit «rio-t4-iPr» (Belarus), and the level of triiodothyronine (T3) — with test-kit «rio-t3-iPr» (Belarus). Expression of surface antigene by peripheral blood lymphocyte was determined with immunofluorescence method with the usage of monoclonal antibodies to surface markers of immune cells LT1, LT3, LT4, LT8, LNK16 and F(ab)2 — fragments of sheep antibody to mouse IgG labeled with FITC («Sorbent», Moscow). Indices of immune and thyroid status were evaluated in 70 people from radiation free areas (control group) and 100 people, residents of Cherkasy region, who were affected by the Chernobyl accident. Age of examined is 18-24 years. According to the results examined people were divided into groups with euthyroidism, hyperthyroidism and hypothyroidism. We have found that examined people from radiation contaminated areas who belong to euthyroidism group have T3 and T4 level not statistically different from control group. In groups with hyperthyroidism rates are significantly higher than in the control group, in groups with hypothyroidism — significantly lower level of triiodothyronine can be seen. The most pronounced changes of cellular immunity can be observed in the group with hypothyroidism. In particular, here we noted the most significant reduction in absolute and relative number of lymphocytes with phenotypes CD3+, CD4+, CD16+, and immunoregulatory index CD4+/CD8+. Thus reducing T3 level leads to inhibition of functionally mature T-lymphocytes, particularly through their helper subpopulation, which runs many immunological reactions. Although subpopulation of cytotoxic T-lymphocytes with CD8+ phenotype does not show a clear dependence on T3 level, the leading role in the implementation of antitumor immunity and in destroy of malignant cells belongs not to them, but to natural killer cells with phenotype CD16+. Reduction of antitumor protection cell level even in patients without clinical signs of thyroid pathologies can cause cancer among people living in the areas contaminated by radionuclides. Most of the examined patients who were exposed to Chernobyl accident factors and who had abnormalities on thyroid hormones, had higher level of T3 and T4. We can assume that the reason for increasing the concentration of triiodothyronine and thyroxine in peripheral blood are compensatory processes that occur in the thyroid. At the same time, significantly reduced level of T cells in examined patients with hypothyroidism may reflect blocking of compensation processes of radiation-induced destruction in thyroid system. Thus, we have found that the changes in the concentration of thyroid hormones, caused by effects of radiation exposure, affect the components of cellular immunity, including factors of antitumor protection. As a result, the population of radiation contaminated areas is in a risk group for viral, endocrine and oncological diseases.

Chernobyl accident, thyroid hormones, cellular immunity

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«Bulletin of problems biology and medicine» Issue 1 part 1 (126), 2016 year, 403-405 pages, index UDK 577.3+612.017:612.118+616.514