A Higher Frequency of Circulating IL-22+CD4+ T Cells in Chinese Patients with Newly Diagnosed Hashimoto’s Thyroiditis

BACKGROUND: IL-22 and IL-17A are implicated in the pathogenesis of autoimmune diseases. However, the role of IL-22(+) and IL-17A(+) CD4(+) T cells in the pathogenesis of Hashimoto's thyroiditis (HT) is not fully understood. This study investigates serum IL-22 and IL-17A levels and determines the frequency of circulating IL-22(+) CD4(+) T cells in HT patients to understand their roles in the pathogenesis of HT. METHODS: The levels of serum IL-22, IL-17A and IFN-γ and the frequency of circulating IL-22(+)CD4(+) and IL-17A(+)CD4(+) T cells in 17 HT patients and 17 healthy controls (HC) were determined by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. The levels of serum free triiodothyronine (FT4), free thyroxine (FT3), thyroid stimulating hormone (TSH), anti-thyroid peroxidase (TPO) and anti-thyroglobulin antibodies (TgAb) by chemiluminescent enzyme immunoassay and radioimmunoassay. RESULTS: The percentages of circulating IL-22(+)CD4(+) and IL-17(+)CD4(+) T cells (p<0.0001, p<0.0001) and the levels of serum IL-22, IL-17A and IFN-γ (p<0.0001, p<0.0001, p = 0.0210) in the HT patients were significantly higher than that in the HC. The percentages of IL-22(+)CD4(+) T cells were positively correlated with Th17 cells (r = 0.8815, p<0.0001) and IL-17A(+)IL-22(+)CD4(+) T cells (r = 0.8914, p<0.0001), but were negatively correlated with Th1 cells (r = -0.6110, p<0.0092) in the HT patients. The percentages of Th22 cells, Th17 cells and IL-17A(+)IL-22(+)CD4(+) T cells were negatively correlated with the levels of serum TSH in the HT patients (r = -0.8402, p<0.0001; r = -0.8589, p<0.0001; r = -0.8289 p<0.0001, respectively). CONCLUSIONS: A higher frequency of circulating IL-22(+)CD4(+) and IL-17A(+)CD4(+) T cells may be associated with the development of HT in Chinese patients.