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.