SLAM Negatively Regulates IL-21 Production in Tfh-Like Cells from Allergic Rhinitis Patients

Abstract Background: Allergic rhinitis (AR) is characterized by type Ⅰ hypersensitivity that is mediated by IgE-induced humoral responses. It is known that follicular helper T cells (Tfh) comprise the key Th cell subset that promotes antibody production. Signaling lymphocytic activation molecule (SLAM) participates in the regulation of the differentiation and function of Tfh cells, but whether this regulation is involved in the pathogenesis of AR is unknown.Methods: CD4+CXCR5+ Tfh-like cells from peripheral blood were detected by flow cytometry. The levels of IL-21 and IgE in serum were tested by ELISA. Blood CD4+CXCR5+ Tfh-like cells were sorted and cultured with anti-SLAM mAb in vitro.Results: The frequencies of circulating CD4+CXCR5+ Tfh-like cells appeared virtually unchanged in AR patients, but the expression of SLAM and SLAM-associated protein (SAP) on circulating Tfh-like cells was significantly decreased. Meanwhile, the level of serum IL-21 was increased in AR patients, and there was a negative correlation between the levels of IL-21 and the expression of SLAM or SAP in CD4+CXCR5+ T cells. Treatment with anti-SLAM mAb resulted in the reduced production of IL-21 by Tfh-like cells in vitro. Additionally, the expression of SLAM on B cells significantly decreased, although the percentages of B cells were increased in AR patients.Conclusions: SLAM negatively regulates the production of IL-21 in CD4+CXCR5+ Tfh-like cells, which contributes to the pathogenesis of AR.