Single nucleotide polymorphisms ofCD244gene predispose to renal and neuropsychiatric manifestations with systemic lupus erythematosus

An update on genetic susceptibility in lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by multiple system involvement and positive serum autoantibodies. Lupus nephritis (LN) is the most common and serious complication of SLE, and it is the main cause of death in patients with SLE. Abnormalities in the immune system lead to LN and involve a variety of cells (T cells, B cells, macrophages, NK cells, etc.), cytokines (interleukin, tumor necrosis factor α, etc.) and their related pathways. Previous studies have shown that the interactions of genetic, epigenetic and environmental factors contribute to the pathogenesis and development of LN. In recent years, one genome-wide association study (GWAS) and a number of gene association studies have explored the susceptibility genes of LN, including immunization-, inflammation-, adhesion- and other pathway-related genes. These genes participate in or suggest the pathogenesis and progression of LN. In this review, we summarize the genetic susceptibility of LN and discuss the possible mechanism underlying the susceptibility genes of LN.

An update on genetic susceptibility in lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by multiple system involvement and positive serum autoantibodies. Lupus nephritis (LN) is the most common and serious complication of SLE, and it is the main cause of death in patients with SLE. Abnormalities in the immune system lead to LN and involve a variety of cells (T cells, B cells, macrophages, NK cells, etc.), cytokines (interleukin, tumor necrosis factor α, etc.) and their related pathways. Previous studies have shown that the interactions of genetic, epigenetic and environmental factors contribute to the pathogenesis and development of LN. In recent years, one genome-wide association study (GWAS) and a number of gene association studies have explored the susceptibility genes of LN, including immunization-, inflammation-, adhesion- and other pathway-related genes. These genes participate in or suggest the pathogenesis and progression of LN. In this review, we summarize the genetic susceptibility of LN and discuss the possible mechanism underlying the susceptibility genes of LN.

Monocyte subsets involved in the development of systemic lupus erythematosus and rheumatoid arthritis

AbstractMonocytes are evolutionally conserved innate immune cells that play essential roles for the protection of the host against pathogens and also produce several inflammatory cytokines. Thus, the aberrant functioning of monocytes may affect not only host defense but also the development of inflammatory diseases. Monocytes are a heterogeneous population with phenotypical and functional differences. Most recent studies have shown that monocytes are divided into three subsets, namely classical, intermediate and non-classical subsets, both in humans and mice. Accumulating evidence showed that monocyte activation is associated with the disease progression in autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). However, it remains to be determined how monocytes contribute to the disease process and which subset is involved. In this review, we discuss the pathogenic role of monocyte subsets in SLE and RA on the basis of current studies by ourselves and others to shed light on the suitability of monocyte-targeted therapies in these diseases.

Signaling lymphocyte activation molecule family in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease characterized by a breakdown in immune tolerance leading to the development of auto-reactive lymphocytes and autoantibodies. Recent findings have provided new insight on the role of the signaling lymphocytic activation molecule family (SLAMF) receptors, a group of nine co-regulatory molecules involved in the activation of hematopoietic cells, and their downstream protein SLAM-associated protein (SAP), into the pathogenesis of SLE. This review summarizes the current knowledge on SLAMF in human SLE immunopathogenesis, and the importance of SLAMF molecules as new therapeutic targets.

The TRPC6 intronic polymorphism, associated with the risk of neurological disorders in systemic lupus erythematous, influences immune cell function

Patients with systemic lupus erythematosus (SLE) carrying a TT genotype for the rs7925662 single nucleotide polymorphism (SNP) in the transient receptor potential canonical channel 6 (TRPC6) gene are more likely to develop neuropsychiatric manifestations (NPSLE). We functionally characterised the effects of TRPC6 on peripheral blood mononuclear cells from 18 patients with SLE and 8 healthy controls with a known genotype. TRPC6 influenced calcium currents, apoptosis rates and cytokine secretion in a disease- and genotype-dependent manner. Cells from TT patients with NPSLE were more dependent on TRPC6 for the generation of calcium currents.

Expression patterns of signaling lymphocytic activation molecule family members in peripheral blood mononuclear cell subsets in patients with systemic lupus erythematosus

Genome-wide linkage analysis studies (GWAS) studies in systemic lupus erythematosus (SLE) identified the 1q23 region on human chromosome 1, containing the Signaling Lymphocytic Activation Molecule Family (SLAMF) cluster of genes, as a lupus susceptibility locus. The SLAMF molecules (SLAMF1-7) are immunoregulatory receptors expressed predominantly on hematopoietic cells. Activation of cells of the adaptive immune system is aberrant in SLE and dysregulated expression of certain SLAMF molecules has been reported. We examined the expression of SLAMF1-7 on peripheral blood T cells, B cells, monocytes, and their respective differentiated subsets, in patients with SLE and healthy controls in a systematic manner. SLAMF1 levels were increased on both T cell and B cells and their differentiated subpopulations in patients with SLE. SLAMF2 was increased on SLE CD4+ and CD8+ T cells. The frequency of SLAMF4+ and SLAMF7+ central memory and effector memory CD8+ T cells was reduced in SLE patients. Naïve CD4+ and CD8+ SLE T cells showed a slight increase in SLAMF3 levels. No differences were seen in the expression of SLAMF5 and SLAMF6 among SLE patients and healthy controls. Overall, the expression of various SLAMF receptors is dysregulated in SLE and may contribute to the immunopathogenesis of the disease.

Altered expression of signalling lymphocyte activation molecule receptors in T-cells from lupus nephritis patients-a potential biomarker of disease activity

Objectives. The aim was to investigate whether the signalling lymphocyte activation molecule (SLAM) signalling pathways contribute to LN and whether SLAM receptors could be valuable biomarkers of disease activity.

Methods. Peripheral blood mononuclear cells from 30National Research Ethics Service SLE patients with biopsy-proven LN were analysed by flow cytometry. Clinical measures of disease activity were assessed. The expression of the SLAM family receptors on T-cell subpopulations [CD4, CD8 and double negative (DN) T cells] was measured and compared between lupus patients with active renal disease and those in remission.

Results. The frequency of CD8 T cells expressing SLAMF3, SLAMF5 and SLAMF7 was significantly lower in LN patients who were in remission. In contrast, these subsets were similar in patients with active renal disease and in healthy individuals. Patients with active nephritis had an increased percentage of circulating monocytes, consistent with a potential role played by these cells in glomerular inflammation. Changes in the frequency of DN T cells positive for SLAMF2, SLAMF4 and SLAMF7 were observed in lupus patients irrespective of the disease activity. We detected alterations in the cellular expression of the SLAM family receptors, but these changes were less obvious and did not reveal any specific pattern. The percentage of DN T cells expressing SLAMF6 could predict the clinical response to B-cell depletion in patients with LN.

Conclusion. Our study demonstrates altered expression of the SLAM family receptors in SLE T lymphocytes. This is consistent with the importance of the SLAM-associated pathways in lupus pathogenesis.

Human Diversity in a Cell Surface Receptor that Inhibits Autophagy

Mutations in genes encoding autophagy proteins have been associated with human autoimmune diseases, suggesting that diversity in autophagy responses could be associated with disease susceptibility or severity. A cellular genome-wide association study (GWAS) screen was performed to explore normal human diversity in responses to rapamycin, a microbial product that induces autophagy. Cells from several human populations demonstrated variability in expression of a cell surface receptor, CD244 (SlamF4, 2B4), that correlated with changes in rapamycin-induced autophagy. High expression of CD244 and receptor activation with its endogenous ligand CD48 inhibited starvation- and rapamycin-induced autophagy by promoting association of CD244 with the autophagy complex proteins Vps34 and Beclin-1. The association of CD244 with this complex reduced Vps34 lipid kinase activity. Lack of CD244 is associated with auto-antibody production in mice, and lower expression of human CD244 has previously been implicated in severity of human rheumatoid arthritis and systemic lupus erythematosus, indicating that increased autophagy as a result of low levels of CD244 may alter disease outcomes.

Selective Loss of Signaling Lymphocytic Activation Molecule Family Member 4-Positive CD8+ T Cells Contributes to the Decreased Cytotoxic Cell Activity in Systemic Lupus Erythematosus

OBJECTIVE

Engagement of signaling lymphocytic activation molecule family member 4 (SLAMF4; CD244, 2B4) by its ligand SLAMF2 (CD48) modulates the function and expansion of both natural killer cells and a subset of cytotoxic CD8+ T cells. Because the cytotoxicity of CD8+ T lymphocytes isolated from patients with systemic lupus erythematosus (SLE) is known to be impaired, the aim of this study was to assess whether the expression and function of the checkpoint regulator SLAMF4 are altered on CD8+ T cells from patients with SLE.

METHODS

The expression of SLAMF4 by T cells from healthy donors and patients with SLE was determined by quantitative polymerase chain reaction and flow cytometry. T cells were activated with anti-CD3 antibody, and degranulation activity was monitored by the surface expression of lysosome-associated membrane protein 1 (LAMP-1; CD107a). The SLAMF4+ and SLAMF4- CD8+ T cell subpopulations were characterized by LAMP-1, perforin, and granzyme B expression and viral peptide-induced proliferation.

RESULTS

SLAMF4 gene and surface protein expression was down-regulated in CD8+ T cells from SLE patients compared with that in cells obtained from healthy donors. Importantly, SLE patients had significantly fewer SLAMF4+ CD8+ T cells compared with healthy donors. SLAMF4- CD8+ T cells from SLE patients had a decreased cytotoxic capacity and decreased proliferative responses to viral peptides. The loss of memory SLAMF4+ CD8+ T cells in SLE patients was linked to the fact that these cells have an increased propensity to lose CD8 expression and become double-negative T cells.

CONCLUSION

A selective loss of SLAMF4+ CD8+ T cells contributes to the compromised ability of T cells from patients with SLE to fight infection.

CD244 is expressed on dendritic cells and regulates their functions

Signaling lymphocytic activation molecule (SLAM) receptors have an important role in the development of immune responses because of their roles, for exampe, in NK cell cytotoxicity and cytokine production by NK, T cells and myeloid cells. The SLAM receptor CD244 (2B4, SLAMf4) is expressed on a variety of immune cell types but most of its functions have been examined on NK and T cells. In the present study, we investigated expression and function of CD244 in murine subsets of dendritic cells (DCs). We report that all subsets of murine DCs examined expressed CD244, although the expression levels of CD244 varied between subsets. Splenic and resident mesenteric lymph node (MLN) DCs from CD244(-/-) mice expressed lower levels of CD86 and MHC class II compared with wild-type mice. Upon Toll-like receptor (TLR) stimulation, no differences in surface expression of these molecules were observed between DCs from CD244(-/-) and wild-type mice. However, splenic DCs from CD244(-/-) mice upon stimulation with TLR binding ligands lipopolysaccharide (LPS) and CpG produced significantly higher levels of pro-inflammatory cytokines. In addition, DCs from CD244(-/-) mice elicited increased NK cell activation in vitro. These data add CD244 to a growing list of immuno-modulatory receptors found on DCs.

Targeting the endothelial progenitor cell surface proteome to identify novel mechanisms that mediate angiogenic efficacy in a rodent model of vascular disease

Endothelial progenitor cells (EPCs) promote angiogenesis, and clinical trials suggest autologous EPC-based therapy may be effective in treatment of vascular diseases. Albeit promising, variability in the efficacy of EPCs associated with underlying disease states has hindered the realization of EPC-based therapy. Here we first identify and characterize EPC dysfunction in a rodent model of vascular disease (SS/Mcwi rat) that exhibits impaired angiogenesis. To identify molecular candidates that mediate the angiogenic potential of these cells, we performed a broad analysis of cell surface protein expression using chemical labeling combined with mass spectrometry. Analysis revealed EPCs derived from SS/Mcwi rats express significantly more type 2 low-affinity immunoglobulin Fc-gamma (FCGR2) and natural killer 2B4 (CD244) receptors compared with controls. Genome-wide sequencing (RNA-seq) and qt-PCR confirmed isoforms of CD244 and FCGR2a transcripts were increased in SS/Mcwi EPCs. EPCs with elevated expression of FCGR2a and CD244 receptors are predicted to increase the probability of SS/Mcwi EPCs being targeted for death, providing a mechanistic explanation for their reduced angiogenic efficacy in vivo. Pathway analysis supported this contention, as "key" molecules annotated to cell death paths were differentially expressed in the SS/Mcwi EPCs. We speculate that screening and neutralization of cell surface proteins that "tag" and impair EPC function may provide an alternative approach to utilizing incompetent EPCs in greater numbers, as circulating EPCs are depleted in patients with vascular disease. Overall, novel methods to identify putative targets for repair of EPCs using discovery-based technologies will likely provide a major advance in the field of regenerative medicine.