Association of Serum IL-35 and TGF-β Levels with the Incidence, Severity, and Treatment Response in Iraqi Patients with Graves' Disease.

Background & Objective: Graves' disease (GD) is a common autoimmune thyroid disorder characterized by thyroid hormone hypersecretion and autoantibody formation against the thyrotropin receptor (TRAb). Interleukin-35 (IL-35), a novel immunosuppressive cytokine of the IL-12 family secreted primarily by regulatory T and B cells, has been implicated in the modulation of autoimmune responses. Transforming growth factor β (TGF-β) is a cytokine with immunoregulatory properties that plays a central role in T-regulatory cell differentiation. This study aimed to investigate serum IL-35 and TGF-β levels in Iraqi patients with GD and assess their association with disease severity, clinical manifestations, and response to carbimazole therapy. Methods: A total of 103 participants were enrolled, including 66 patients with GD (mean age, 41.6 [SD, 13.95] years) and 37 healthy controls (mean age, 37.43 [SD, 10.25] years). Serum IL-35 and TGF-β concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Results: IL-35 levels were significantly reduced in untreated GD patients compared with healthy controls and partially increased after carbimazole therapy ( Conclusion: IL-35 may serve as a promising biomarker for monitoring disease activity, prognosis, and therapeutic response in patients with GD.