Serum IFN-γ, IL-21 and Circulating iNKT Cells as Immunological Markers in Untreated Hashimoto’s Thyroiditis

Abstract

Hashimoto’s thyroiditis (HT) is an organ-specific autoimmune disease in which inflammatory cytokines and innate-like lymphocyte subsets may reflect active immune dysregulation. Objective: This article evaluates serum interferon-gamma (IFN-γ), interleukin-21 (IL-21), and circulating invariant natural killer T (iNKT; CD3+6B11+) cells in untreated newly diagnosed HT patients. Methods: A case-control study included 50 untreated HT patients and 50 healthy controls. IFN-γ and IL-21 were measured by ELISA, and iNKT cells were detected by flow cytometry. Diagnostic accuracy was assessed by receiver-operating-characteristic analysis. Results: IFN-γ was markedly higher in HT patients than controls (27.84±8.40 vs. 6.24±1.81 pg/mL; P=0.001). IL-21 was also elevated (46.47±10.42 vs. 20.21±3.53 pg/mL; P=0.001). iNKT cells increased significantly (0.54±0.29% vs. 0.31±0.13%; P=0.001). Receiver Operating Characteristic (ROC) analysis showed potential adjunct biomarkers requiring external validation for IFN-γ (AUC=0.949) and IL-21 (AUC=0.930), while iNKT cells showed moderate diagnostic performance (AUC=0.751). Conclusion: IFN-γ and IL-21 represent potential adjunct biomarkers requiring external validation, whereas iNKT cells provide significant but weaker supportive information.