Expression and Function of the Costimulatory Receptor SLAMF1 Is Altered in Lymphocytes From Patients With Autoimmune Thyroiditis

Context: Signaling lymphocytic activation molecule family 1 (SLAMF1) is a costimulatory receptor expressed by most immune cells. Its role in autoimmune thyroid disease (AITD) is not well known. Objective: To analyze the expression and function of the costimulatory receptor SLAMF1 in lymphocytes of patients with AITD. Design: Cross-sectional, prospective, single-center study. Setting: Department of Endocrinology, Hospital Universitario de la Princesa, Madrid. Patients: Twenty-eight patients with AITD (17 with Graves disease and 11 with Hashimoto thyroiditis) and 21 controls. Intervention: Multiparametric flow cytometry and immunofluorescence techniques to analyze the expression of SLAMF1 in peripheral blood (n = 28) and thyroid tissue (n = 5) mononuclear cells. Assay of inhibition of cellular proliferation to study the function of SLAMF1 in CD4(+) CD25(+) T regulatory (Treg) cells. Main Outcome Measure: Expression levels and the function of SLAMF1 in lymphocytes in AITD patients and controls. Results: Expression of SLAMF1 was significantly increased in peripheral blood CD4(+), T helper 17, and CD19(+) B cells from AITD patients. Immunofluorescence microscopy detected the presence of SLAMF1(+) lymphocytes in thyroid inflammatory cell infiltrate. Functional studies showed that SLAMF1 engagement in Treg cells increased their suppressive function in healthy controls but not in AITD patients. Conclusions: The altered expression of SLAMF1, as well as its defective function observed in patients with AITD, may have a relevant role in the defective immune-regulatory function observed in this condition.