Interleukin 18 and transforming growth factor β1 in the serum of patients with Graves' ophthalmopathy treated with corticosteroids

Abstract

Interleukin-18 (IL-18), a novel cytokine of the IL-1 family, and TGFβ1 have been lately identified in several thyroid autoimmune diseases. The aim of this study was to estimate the influence of corticosteroids on serum IL-18 and TGFβ1 in Graves' ophthalmopathy (GO) patients and to assess their potential as a guideline of immunosuppressive therapy. The study was carried out in three groups of subjects: (1) 17 patients with clinical symptoms of ophthalmopathy (GO) that underwent corticosteroid therapy consisting of intravenous methylprednisolone (MP) infusions and subsequent treatment with oral prednisone (P); (2) 14 patients with euthyroid Graves' disease (Gd) without symptoms of ophthalmopathy; (3) 12 healthy volunteers age- and sex-matched to groups 1 and 2. The serum levels of IL-18 and TGF β1 were determined by the ELISA method. Thyroid receptor antibodies (TRAB) were estimated by the RIA method. Levels of IL-18 were significantly higher in both GO [340±109 pg/ml (p<0.02)] and Gd individuals [308±89 pg/ml (p<0.05)] as compared to the control group (238±88 pg/ml). There were no significant differences in TGFβ1 concentrations between studied groups. TRAB values were significantly increased in both GO (p<0.001) and Gd individuals (p<0.001) as compared to the controls. In coticosteroid-responsive patients we have found a significant decrease in IL-18 serum concentration as compared to the pretreatment values. We did not find any correlation between IL-18 or TGFβ1 and TRAB, duration of GO, clinical activity score (CAS) or proptosis. Our results suggest that efficient corticosteroid therapy in patients with Graves' ophthalmopathy may be related to its influence on systemic IL-18.