THYROID STATUS AND ITS CORRELATION WITH THE FUNCTIONAL ACTIVITY OF IMMUNOCYTES

Abstract

Pathogenesis studies in thyroid autoimmune diseases take a specific place among endocrine disorders, due to high prevalence of these pathologies, thus representing an urgent problem of the modern medicine. Their triggering mechanisms of their are still unknown. Changes of thyroid status in cases of nonthyroid pathology, e.g., during development of «nonthyroidal syndrome», may launch synthesis of some functionally opposite cytokines by immunocytes, with subsequent loss of tolerance to thyroid autoantigens. One may suggest that mast cells may potentially influence secretory activity of thyrocytes via Toll-like receptors, and, therefore, induce synthesis of opposite cytokines, with subsequent loss of auto-tolerance. The mast cells found in thyroid gland affected by an autoimmune disorder may also regulate functional activity of immunocytes and hormone-secreting cells due to molecular effects of secretable substances. The mechanisms prevailing in autoimmune thyroid disease are, however, widely unknown. These effects may involve either primary activation of mast cells by thyroid hormones, or secondary changes of thyroid status. To address these issues, we studied some features of mast cells response and production of functionally opposite cytokines (IL-1β, IL-10, IFNγ, TNFα) in experimental thyrotoxicosis and hypothyroidism. To boost the immune response, a subgroup of experimental animals with thyrotoxicosis was treated with recombinant interleukin-2. Specific changes of IFNγ/IL-10 ratio depending on thyroid status confirmed a role of opposite cytokine balance for development of different pathological variants. A significant increase in the Th1-marker cytokines revealed at the organ level in cases of thyrotoxicosis argued for direct involvement of thyroid hormones into the immune regulation, as confirmed by a focal infiltration of a thyroid gland with mast cells, along with significant increase in pro-inflammatory cytokines at systemic and organ levels. A hypothesis on possible reception of thyroid hormones by immune cells is in accordance with intensive correlations between the levels of opposite cytokines in target organ and contents of thyroid hormones in peripheral blood. A regulatory role of interleukin-2 was suggested as a factor of keeping balance for opposite cytokines and changing vector of immune response in case of altered thyroid status. The results of our study presume an important role of mast cells and balance of opposite cytokines in pathogenesis of thyroid dysfunction. Further studies are required, in order to clarify the mechanisms of interaction between thyroid hormones and immune cells.