Both cellular and humoral responses play important roles in the pathogenesis of Hashimoto's thyroiditis (HT). However, the immunological differences between euthyroid (mild HT) and hypothyroid (severe HT) patients are unknown. This study aimed to investigate the distribution of lymphocyte subsets and cytokine profiles in HT patients with differences in thyroid function.
Peripheral blood was drawn from 18 healthy controls and 54 HT patients (33 patients with mild HT, 21 patients with severe HT). The percentages of B cell subsets, T cell subsets and NK cells were analyzed by flow cytometry. The levels of IL-21 and Bcl-6 mRNA were assessed using real-time PCR. The levels of serum IFN-γ, TNF-α, TGF-β, IL-4, IL-6, IL-10 and a proliferation-inducing ligand (APRIL) were measured by ELISA or cytometric bead array.
The percentages of double-negative memory B cells, plasma cells, Tfh cells and Tc17 cells were higher in HT patients than in the healthy controls. The percentages of Tc17 cells and NK cells were higher in the patients with severe HT than in the patients with mild HT. The levels of serum APRIL, IL-6 and IL-10 were higher in the patients with severe HT than in those with mild HT. The percentage of NK cells was positively correlated with TSH levels in the HT patients.
Our data indicate that the distribution of lymphocyte subsets and cytokine profiles is aberrant in HT patients, and the increased percentages of Tc17 cells and NK cells and increased cytokine levels might be involved in the progression of HT.