TIGIT-Fc fusion protein alleviates murine lupus nephritis through the regulation of SPI-B-PAX5-XBP1 axis-mediated B-cell differentiation

TIGIT deficiency promotes autoreactive CD4+ T-cell responses through a metabolic‒epigenetic mechanism in autoimmune myositis

Polymyositis (PM) is a systemic autoimmune disease characterized by muscular inflammatory infiltrates and degeneration. T-cell immunoreceptor with Ig and ITIM domains (TIGIT) contributes to immune tolerance by inhibiting T cell-mediated autoimmunity. Here, we show that a reduced expression of TIGIT in CD4+ T cells from patients with PM promotes these cells' differentiation into Th1 and Th17 cells, which could be rescued by TIGIT overexpression. Knockout of TIGIT enhances muscle inflammation in a mouse model of experimental autoimmune myositis. Mechanistically, we find that TIGIT deficiency enhances CD28-mediated PI3K/AKT/mTOR co-stimulatory pathway, which promotes glucose oxidation, citrate production, and increased cytosolic acetyl-CoA levels, ultimately inducing epigenetic reprogramming via histone acetylation. Importantly, pharmacological inhibition of histone acetylation suppresses the differentiation of Th1 and Th17 cells, alleviating muscle inflammation. Thus, our findings reveal a mechanism by which TIGIT directly affects the differentiation of Th1 and Th17 T cells through metabolic‒epigenetic reprogramming, with important implications for treating systemic autoimmune diseases.

Compromised B-cell homeostasis: Unraveling the link between major depression, infection and autoimmune disorders

BACKGROUND

Major depression can increase susceptibility to viral infections and autoimmune diseases. B cell responses are crucial for immune defense against infections but can trigger autoimmunity when deregulated. However, it remains unclear whether compromised B-cell homeostasis in major depression contributes to an increased risk of infection and autoimmunity.

METHODS

Chronic unpredictable mild stress (CUMS) procedure was applied to adult C57BL/6 J mice to generate a reliable depression model. Mice were immunized with (4-hydroxy-3-nitrophenyl) acetyl (NP) keyhole limpet hemocyanin (NP-KLH) to elicit B-cell-mediated humoral immune responses. CUMS mice were subjected to a collagen-induced arthritis model or a Bm12-induced systemic lupus erythematosus model to assess the contribution of major depression to autoimmunity. RNA sequencing was performed to understand the effects of CUMS on B-cell homeostasis at the transcriptomic level.

RESULTS

CUMS mice exhibited an impaired humoral immune response, as evidenced by reduced germinal centers (GCs), plasma cells, and antigen-specific antibodies. Unimmunized CUMS mice displayed aberrant spontaneous expansion of GC B cells, plasma cells, age-associated B cells and autoantibody production. CUMS mice also demonstrated a greater exacerbation of autoimmune manifestations. RNA sequencing revealed that genes involved in B-cell-mediated immune response were downregulated in B cells from CUMS mice, while the pathways related to autoimmunity seem to be upregulated.

LIMITATIONS

Further research is needed to understand the specific targets, mechanisms, and role of B cell dysfunction in major depression.

CONCLUSIONS

Our results provide novel insights into B-cell-dependent mechanisms that involve the association of increased susceptibility to infections and autoimmunity in major depression.

Single-cell analyses of intestinal epithelium reveal the dysregulation of gut immune microenvironment in systemic lupus erythematosus

BACKGROUND

The small intestine harbors a rich array of intestinal intraepithelial lymphocytes (IELs) that interact with structural cells to collectively sustain gut immune homeostasis. Dysregulation of gut immune homeostasis was implicated in the pathogenesis of multiple autoimmune diseases, however, whether this homeostasis is disrupted in a lupus autoimmune background remains unclear.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) analyses to elucidate immune and structural milieu in the intestinal epithelium of MRL/Lpr lupus mice (Lpr mice) and MRL/Mpj control mice (Mpj mice). Comprehensive analyses including unsupervised clustering, trajectories, and cellular communication were performed. The primary findings from scRNA-seq were further validated by quantitative polymerase chain reaction (qPCR), flow cytometry, and in vivo experiments including selenium supplementation.

RESULTS

We observed a significant reduction in CD8αα + IELs, accompanied by a marked increase in CD8αβ + IELs in Lpr mice. Additionally, subsets of CD8 + IELs exhibiting significantly enhanced effector functions were found to be markedly enriched in Lpr mice. Intercellular communication patterns within intestinal epithelial immune and structural cells were found to be specifically altered in Lpr mice. Moreover, scRNA-seq revealed significantly decreased intestinal TCRγδ T cells (γδT) associated with reduced aryl-hydrocarbon receptor repressor (AHRR) expression and subsequent oxidative stress and ferroptosis in Lpr mice. Antioxidant selenium effectively reversed the loss of γδT in Lpr mice, improved the gut barrier, and alleviated lupus symptoms.

CONCLUSIONS

Our high-resolution single-cell atlas enhances the understanding of the immune and structural milieu of intestinal epithelium in lupus and provides new insights into lupus pathogenesis mediated by intestinal immune dysregulation.

Organ-based characterization of B cells in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic, inflammatory, and progressive autoimmune disease. The unclear pathogenesis, high heterogeneity, and prolonged course of the disease present significant challenges for effective clinical management of lupus patients. Dysregulation of the immune system and disruption of immune tolerance, particularly through the abnormal activation of B lymphocytes and the production of excessive autoantibodies, lead to widespread inflammation and tissue damage, resulting in multi-organ impairment. Currently, there is no systematic review that examines the specificity of B cell characteristics and pathogenic mechanisms across various organs. This paper reviews current research on B cells in lupus patients and summarizes the distinct characteristics of B cells in different organs. By integrating clinical manifestations of organ damage in patients with a focus on the organ-specific features of B cells, we provide a new perspective on enhancing the efficacy of lupus-targeted B cell therapy strategies.

Emerging roles of checkpoint molecules on B cells

Immune checkpoint molecules, including both co-inhibitory molecules and co-stimulatory molecules, are known to play critical roles in regulating T-cell responses. During the last decades, immunotherapies targeting these molecules (such as programmed cell death 1 (PD-1), and lymphocyte activation gene 3 (LAG-3)) have provided clinical benefits in many cancers. It is becoming apparent that not only T cells, but also B cells have a capacity to express some checkpoint molecules. These were originally thought to be only the markers for regulatory B cells which produce IL-10, but recent studies suggest that these molecules (especially T-cell immunoglobulin and mucin domain 1 (TIM-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT), and PD-1) can regulate intrinsic B-cell activation and functions. Here, we focus on these molecules and summarize their characteristics, ligands, and functions on B cells.

Blockade of OX40/OX40L signaling using anti-OX40L alleviates murine lupus nephritis

Genetic variants of the OX40 ligand (OX40L) locus are associated with the risk of systemic lupus erythematosus (SLE), it is unclear how the OX40L blockade delays the lupus phenotype. Therefore, we examined the effects of an anti-OX40L antibody in MRL/Lpr mice. Next, we investigated the effect of anti-OX40L on immunosuppression in keyhole limpet hemocyanin-immunized C57BL/6J mice. In vitro treatment of anti-OX40L in CD4+ T and B220+ B cells was used to explore the role of OX40L in the pathogenesis of SLE. Anti-OX40L alleviated murine lupus nephritis, accompanied by decreased production of anti-dsDNA and proteinuria, as well as lower frequencies of splenic T helper (Th) 1 and T-follicular helper cells (Tfh). In keyhole limpet hemocyanin-immunized mice, decreased levels of immunoglobulins and plasmablasts were observed in the anti-OX40L group. Anti-OX40L reduced the number and area of germinal centers. Compared with the control IgG group, anti-OX40L downregulated CD4+ T-cell differentiation into Th1 and Tfh cells and upregulated CD4+ T-cell differentiation into regulatory T cells in vitro. Furthermore, anti-OX40L inhibited toll-like receptor 7-mediated differentiation of antibody-secreting cells and antibody production through the regulation of the SPIB-BLIMP1-XBP1 axis in B cells. These results suggest that OX40L is a promising therapeutic target for SLE.

Landscape of gut mucosal immune cells showed gap of follicular or memory B cells into plasma cells in immunological non-responders

BACKGROUND

The gut is an important site for human immunodeficiency virus (HIV) infection and immune responses. The role of gut mucosal immune cells in immune restoration in patients infected with HIV undergoing antiretroviral therapy remains unclear.

METHODS

Ileocytes, including 54 475 immune cells, were obtained from colonoscopic biopsies of five HIV-negative controls, nine immunological responders (IRs), and three immunological non-responders (INRs) and were analyzed using single-cell RNA sequencing. Immunohistochemical assays were performed for validation. The 16S rRNA gene was amplified using PCR in faecal samples to analyze faecal microbiota. Flow cytometry was used to analyze CD4+ T-cell counts and the activation of T cells.

RESULTS

This study presents a global transcriptomic profile of the gut mucosal immune cells in patients infected with HIV. Compared with the IRs, the INRs exhibited a lower proportion of gut plasma cells, especially the IGKC+IgA+ plasma cell subpopulation. IGKC+IgA+ plasma cells were negatively associated with enriched f. Prevotellaceae the INRs and negatively correlated with the overactivation of T cells, but they were positively correlated with CD4+ T-cell counts. The INRs exhibited a higher proportion of B cells than the IRs. Follicular and memory B cells were significantly higher in the INRs. Reduced potential was observed in the differentiation of follicular or memory B cells into gut plasma cells in INRs. In addition, the receptor-ligand pairs CD74_MIF and CD74_COPA of memory B/ follicular helper T cells were significantly reduced in the INRs, which may hinder the differentiation of memory and follicular B cells into plasma cells.

CONCLUSIONS

Our study shows that plasma cells are dysregulated in INRs and provides an extensive resource for deciphering the immune pathogenesis of HIV in INRs.

KEY POINTS

An investigation was carried out at the single-cell-level to analyze gut mucosal immune cells alterations in PLWH after ART. B cells were significantly increased and plasma cells were significantly decreased in the INRs compared to the IRs and NCs. There are gaps in the transition from gut follicular or memory B cellsinto plasma cells in INRs.

T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain as a promising immune checkpoint target for the treatment of SLE

Immune checkpoints (ICs) play a pivotal role in orchestrating immune regulation, crucial for the maintenance of immune tolerance and prevention of autoimmune diseases. One noteworthy example among these immune regulators is T cell immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT). The TIGIT pathway's inhibition or the absence of TIGIT has been linked to the hyperactivation and excessive proliferation of T cells, rendering individuals more susceptible to autoimmune diseases and exacerbating inflammatory responses. Conversely, the activation of TIGIT has exhibited promising outcomes in ameliorating autoimmune disorders, as observed in murine models of systemic lupus erythematosus (SLE). Consequently, a judicious exploration of the co-inhibitory axis appears warranted for the effective management of pathogenic immune responses in SLE. In light of compelling evidence, this review undertakes a comprehensive examination of TIGIT's characteristics within the context of autoimmunity, offering insights into its potential as a therapeutic target for SLE.

Effect of BAFF blockade on the B cell receptor repertoire and transcriptome in a mouse model of systemic lupus erythematosus

Introduction

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. Anti-B-cell-activating factor (BAFF) therapy effectively depletes B cells and reduces SLE disease activity. This research aimed to evaluate the effect of BAFF blockade on B cell receptor (BCR) repertoire and gene expression.

Methods

Through next-generation sequencing, we analyzed gene expression and BCR repertoire in MRL/lpr mice that received long-term anti-BAFF therapy. Based on gene expression profiles, we predicted the relative proportion of immune cells using ImmuCellAI-mouse, validating our predictions via flow cytometry and FluoroSpot.

Results

The loss of BCR repertoire diversity and richness, along with increased clonality and differential frequency distribution of the immunoglobulin heavy chain variable (IGHV) segment gene usage, were observed in BAFF-blockade mice. Meanwhile, the distribution of complementarity-determining region 3 (CDR3) length and CDR3 amino acid usage remained unaffected. BAFF blockade resulted in extensive changes in gene expression, particularly that of genes related to B cells and immunoglobulins. Besides, the tumor necrosis factor (TNF)-α responses and interferon (IFN)-α/γ were downregulated, consistent with the decrease in IFN-γ and TNF-α serum levels following anti-BAFF therapy. In addition, BAFF blockade significantly reduced B cell subpopulations and plasmacytoid dendritic cells, and caused the depletion of antibody-secreting cells.

Discussion

Our comparative BCR repertoire and transcriptome analyses of MRL/lpr mice subjected to BAFF blockade provide innovative insights into the molecular pathophysiology of SLE.