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

Signaling lymphocytic activation molecule (SLAM) and SLAM-associated protein (SAP) play important role in inflammatory and autoimmune diseases. Our study is aimed at detecting the expression of SLAM and SAP in patients with Graves’ disease (GD) and analyzing the effect of SLAM/SAP on circulating blood CD4+CXCR5+Foxp3+ follicular regulatory T (Tfr) cells. 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. Our results suggested that the SLAM/SAP signaling pathway is involved in the decrease of circulating Tfr cells in Graves’ disease.

Computational Analysis Reveals a Critical Point Mutation in the N-Terminal Region of the Signaling Lymphocytic Activation Molecule Responsible for the Cross-Species Infection with Canine Distemper Virus

Infection of hosts by morbilliviruses is facilitated by the interaction between viral hemagglutinin (H-protein) and the signaling lymphocytic activation molecule (SLAM). Recently, the functional importance of the n-terminal region of human SLAM as a measles virus receptor was demonstrated. However, the functional roles of this region in the infection process by other morbilliviruses and host range determination remain unknown, partly because this region is highly flexible, which has hampered accurate structure determination of this region by X-ray crystallography. In this study, we analyzed the interaction between the H-protein from canine distemper virus (CDV-H) and SLAMs by a computational chemistry approach. Molecular dynamics simulations and fragment molecular orbital analysis demonstrated that the unique His28 in the N-terminal region of SLAM from Macaca is a key determinant that enables the formation of a stable interaction with CDV-H, providing a basis for CDV infection in Macaca. The computational chemistry approach presented should enable the determination of molecular interactions involving regions of proteins that are difficult to predict from crystal structures because of their high flexibility.

Computational Analysis Reveals a Critical Point Mutation in the N-Terminal Region of the Signaling Lymphocytic Activation Molecule Responsible for the Cross-Species Infection with Canine Distemper Virus

Infection of hosts by morbilliviruses is facilitated by the interaction between viral hemagglutinin (H-protein) and the signaling lymphocytic activation molecule (SLAM). Recently, the functional importance of the N-terminal region of human SLAM as a measles virus receptor was demonstrated. However, the functional roles of this region in the infection process by other morbilliviruses and host range determination remain unknown partly because this region is highly flexible, which has hampered accurate structure determination of this region by X-ray crystallography. In this study, we analyzed the interaction between the H-protein from canine distemper virus (CDV-H) and SLAMs by a computational chemistry approach. Molecular dynamics simulations and fragment molecular orbital analysis demonstrated that the unique His28 in the N-terminal region of SLAM from Macaca is a key determinant that enables formation of a stable interaction with CDV-H, providing a basis for CDV infection in Macaca. The computational chemistry approach presented should enable determination of molecular interactions involving regions of proteins that are difficult to predict from crystal structures because of their high flexibility.

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

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.

Immune Functions of Signaling Lymphocytic Activation Molecule Family Molecules in Multiple Myeloma

The signaling lymphocytic activation molecule (SLAM) family receptors are expressed on various immune cells and malignant plasma cells in multiple myeloma (MM) patients. In immune cells, most SLAM family molecules bind to themselves to transmit co-stimulatory signals through the recruiting adaptor proteins SLAM-associated protein (SAP) or Ewing’s sarcoma-associated transcript 2 (EAT-2), which target immunoreceptor tyrosine-based switch motifs in the cytoplasmic regions of the receptors. Notably, SLAMF2, SLAMF3, SLAMF6, and SLAMF7 are strongly and constitutively expressed on MM cells that do not express the adaptor proteins SAP and EAT-2. This review summarizes recent studies on the expression and biological functions of SLAM family receptors during the malignant progression of MM and the resulting preclinical and clinical research involving four SLAM family receptors. A better understanding of the relationship between SLAM family receptors and MM disease progression may lead to the development of novel immunotherapies for relapse prevention.

SLAM family receptors control pro-survival effectors in germinal center B cells to promote humoral immunity

Expression of the signaling lymphocytic activation molecule (SLAM)–associated protein (SAP) is critical for the germinal center (GC) reaction and T cell–dependent antibody production. However, when SAP is expressed normally, the role of the associated SLAM family receptors (SFRs) in these processes is nebulous. Herein, we established that in the presence of SAP, SFRs suppressed the expansion of the GC reaction but facilitated the generation of antigen-specific B cells and antibodies. SFRs favored the generation of antigen-reactive B cells and antibodies by boosting expression of pro-survival effectors, such as the B cell antigen receptor (BCR) and Bcl-2, in activated GC B cells. The effects of SFRs on the GC reaction and T cell–dependent antibody production necessitated expression of multiple SFRs, both in T cells and in B cells. Hence, while in the presence of SAP, SFRs inhibit the GC reaction, they are critical for the induction of T cell–mediated humoral immunity by enhancing expression of pro-survival effectors in GC B cells.

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

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.