Patients With Autoimmune Thyroiditis Show Diminished Levels and Defective Suppressive Function of Tr1 Regulatory Lymphocytes

Context: T regulatory type 1 (Tr1) cells are a subpopulation of T lymphocytes (CD4(+)CD49(+)LAG-3(+) IL-10(+)) that exert a considerable immunosuppressive effect. However, their possible role in autoimmune thyroid disease (AITD) has not been explored so far. Purpose: To analyze the levels and function of Tr1 cells in peripheral blood and thyroid tissue of patients with AITD. Design: Cases and controls, observational study. Setting: Department of Endocrinology, Hospital Universitario de la Princesa, Madrid, Spain. Patients: Thirty-eight patients with AITD (23 with Graves disease and 15 with Hashimoto thyroiditis) and 26 controls. Intervention: Multiparametric flow cytometry and immunofluorescence techniques were used to analyze the levels in peripheral blood (n = 38) and thyroid mononuclear cells (n = 5). An in vitro assay of suppression of cellular activation and cytokine release was performed to study the function of Tr1 cells. Main Outcome Measure: Levels and function of Tr1 cells in patients with AITD and controls. Results: Levels of Tr1 cells were significantly diminished in peripheral blood from patients with AITD. Functional studies showed that Tr1 cells from patients with AITD exhibit a diminished suppressive function compared with healthy controls. Tr1 levels were associated with disease severity, including longer duration of the disease and ophthalmopathy activity, and with autoantibody titers. Conclusions: The low levels of Tr1 cells and their diminished function may have a relevant role in the defective immune-regulatory function characteristic of patients with AITD.