Roles of Thyroid Hormones, Mast Cells, and Inflammatory Mediators in the Initiation and Progression of Autoimmune Thyroid Diseases.

Background: Interrelation between thyrocytes and immunocytes has been established. However, the roles of mast cells and thyroid hormones in the triggering mechanism of thyroid autoimmune processes have been insufficiently investigated. This study evaluated the role of thyroid hormones and mast cells in the mechanisms of losing tolerance to thyroid autoantigens.

Materials And Methods: Two groups of patients were studied: patients with Graves' disease and patients with nodular euthyroid goiter. Wistar rats with induced exogenous hypothyroidism, thyrotoxicosis, and thyrotoxicosis in parallel with administration of interleukin-2 were used. The levels of hormones, autoantibodies, and cytokines in the serum and thyroid tissue were analyzed through the enzyme-linked immunosorbent assay. Morphological verification was performed through the immune-histochemical method with antibodies against tryptase and CD86. Transmission electron microscopy and laser confocal microscopy were used.

Results: In both Graves' disease and induced thyrotoxicosis, we detected a significant increase in the levels of interferon-γ, active interfollicular infiltration and degranulation of mast cells, and the intrathyroid overexpression of CD86. Complex analysis of the rat's thyroid morphofunctional state and systemic and local levels of cytokines in induced thyrotoxicosis and hypothyroidism demonstrated an increase of intrathyroid degranulation of mast cells and a drastic disruption of IFNγ/IL10 balance.

Conclusions: When exposed to excessive amounts of thyroid hormones, an inflammatory response is triggered in the thyroid gland, and mast cells overexpress costimulating CD86 in the thyroid. This finding confirms their possible involvement in auto-antigen presentation. Significant increase in the levels of interferon-γ shows a determining influence of cytokine on the progression of the pathological process.