The pathogenic role of Th17 cell pathway in autoimmune thyroid diseases

Th17 cells have been established to play a significant role in the pathogenesis of thyroid autoimmunity. Furthermore, selenium deficiency can impair the differentiation of Th cells, leading to cellular and humoral response dysfunction. We aimed to assess the levels of Th17 cytokines levels and the selenium status in treatment-naïve patients with new-onset Graves’ disease (GD) or Hashimoto’s thyroiditis (HT). Eighty-eight participants were recruited for this study: 11 hyperthyroid GD patients, 41 patients with HT, and 26 age- and sex-matched healthy subjects as controls. Plasma levels of IL-17a, IL-22, IL-23, IL-6, and IL-10 were detected by xMAP technology (Magpix system; Luminex Corporation, USA). Tests were performed in accordance with the manufacturer’s instructions (Cat#: HTH17MAG-14K; Kit Lot#: 3323752; Milliplex). The plasma selenium level was determined fluorometrically by using the fluorescence spectrophotometer. We did not find significant differences in IL-17a, IL-22, IL-6, IL-23, or IL-10 levels among the HT patients, GD patients, and controls. However, in the HT patients, IL-22 was correlated with IL-6, IL-10, and IL-23, while IL-17a levels were positively correlated with IL-23, IL-22, IL-6, and IL-10. In the GD group, IL-17a levels were positively correlated with IL-22, IL-23, and IL-10; IL-22 was positively correlated with IL-23, IL-6, and IL-10. In addition, FT3 was positively correlated with IL-17a, IL-23, and IL-10; and FT4 was positively correlated with IL-17a and IL-10 levels in GD patients. No difference in selenium levels was observed among the studied groups. Interestingly, plasma selenium levels were negatively correlated with anti-thyroid peroxidase antibody titres in the HT patients. Th17 cytokines were positively correlated with the severity of hyperthyroidism, suggesting their possible role in GD pathogenesis. The selenium status of the Latvian patients with GD or HT was at a suboptimal level.This study was supported by the Latvian Council of Science (Grant No: lzp-2018/2-0059).