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.