Objective: To explore the role of CD4⁺ CD25⁺ Foxp3⁺ Treg/CD4⁺ IL-17A(+)Th17 cells and the related cytokines in Graves' ophthalmopathy.
Methods: Based on clinical activity scores (CAS), we divided patients with untreated Graves' ophthal- mopathy into active group (AGO group with CAS ≥ 3 (15 cases) and non-active group (NGO group) with CAS<3 (15 cases), with another 15 patients with untreated Graves' disease free of eye symptoms (GD group) and 15 normal subjects as controls. Peripheral venous blood Treg/Th17 cell ratio was determined using flow cytometry. RT-PCR was used to detect the mRNA expression levels of Treg-specific transcription factor Foxp3 and Th17-specific transcription factor RORγt. Enzyme-linked immunosorbent assay (ELISA) was used to detect the serum levels of Th17 cell-related cytokines (IL-17A, IL-23, and IL-6) and Treg-related cytokines (TGF-β, IL-10, and IL-35).
Results: Compared with the normal subjects, the patients in GD, NGO, AGO groups all showed significantly increased Th17 cell count (P<0.05), which was the highest in AGO group. RT-PCR results revealed significantly increased RORγt in GD, NGO, and AGO groups, also the highest in AGO group. Serum IL-17A, IL-23, and IL-6 levels all showed significant increments in GD, NGO, and AGO groups (P<0.05), especially in AGO group. Among the Treg-related cytokines, TGF-β and IL-35 levels decreased (P<0.05) but IL-10 increased significantly (P<0.05) in GD, NGO, AGO groups.
Conclusion: Decreased immunosuppressive capacity of Treg cells can be an important factor in the pathogenesis of Graves' ophthalmopathy. Th17 cells may also participate in the occurrence and progression of Graves' ophthalmopathy and can serve along with related cytokines as novel indicators of the disease activity. Impaired Treg/Th17 balance may importantly contribute to the occurrence of Graves' ophthalmopathy.