SLAM/SAP Decreased Follicular Regulatory T Cells in Patients With Graves’ Disease 

Abstract

Background: Signaling lymphocytic activation molecule (SLAM) and SLAM-associated protein (SAP) play important role in inflammatory and autoimmune diseases. Our study aimed to detect the expression of SLAM and SAP in patients with Graves’ disease (GD) and analyze the effect of SLAM/SAP on circulating blood CD4+CXCR5+ Foxp3+ follicular regulatory T (Tfr) cells.Methods: The expression of SLAM and SAP was assessed by flow cytometry and real-time PCR. The percentages of IFN-γ+ cells, IL-4+ cells, IL-17+ cells and Foxp3+ cells in CD4+CXCR5+ T cells and circulating CD4+CXCR5+ Foxp3+ Tfr cells after treatment with anti-SLAM and anti-CD3 antibodies were also assessed by flow cytometry. The correlations between the percentages of Tfr cells and the levels of autoantibodies as well as SAP were analyzed.Results: The level of SAP in CD4+CXCR5+ T cells and the level of SLAM on CD19+ B cells were significantly increased in the patients with GD, but no significant difference in the level of SLAM on CD4+CXCR5+ T cells was observed between the patients with GD and the healthy controls. A decrease in the percentage of Foxp3+ cells in CD4+CXCR5+ T cells was observed following anti-SLAM treatment, but the percentages of IFN-γ+ cells, IL-4+ cells and IL-17+ cells showed no obvious differences. The proportion of circulating Tfr cells was decreased in the patients with GD, and the proportion of circulating Tfr cells had a negative correlation with the level of SAP in CD4+CXCR5+ T cells and the levels of autoantibodies in the serum of the patients with GD.Conclusions: Our results indicate that the SLAM/SAP signaling pathway regulates Tfr cells, which may be involved in the pathogenesis of Graves’ disease.