TNFRSF13B genotypes control immune-mediated pathology by regulating the functions of innate B cells

Charge-based immunoreceptor signalling in health and disease

Immunoreceptors have crucial roles in sensing environmental signals and initiating immune responses to protect the host. Dysregulation of immunoreceptor signalling can therefore lead to a range of diseases, making immunoreceptor-based therapies a promising frontier in biomedicine. A common feature of various immunoreceptors is the basic-residue-rich sequence (BRS), which is a largely unexplored aspect of immunoreceptor signalling. The BRS is typically located in the cytoplasmic juxtamembrane region of immunoreceptors, where it forms dynamic interactions with neighbouring charged molecules to regulate signalling. Loss or gain of the basic residues in an immunoreceptor BRS has been linked to severe human diseases, such as immunodeficiency and autoimmunity. In this Perspective, we describe the role of BRSs in various immunoreceptors, elucidating their signalling mechanisms and biological functions. Furthermore, we highlight pathogenic mutations in immunoreceptor BRSs and discuss the potential of leveraging BRS signalling in engineered T cell-based therapies.

Association of TNFRSF13B Gene Polymorphisms With SARS-CoV-2 Infection, Severity, and Humoral Immune Response in a Moroccan Population

BACKGROUND AND AIMS

Genetic factors, including polymorphisms in the TNFRSF13B gene, which regulates humoral immunity, can influence susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study aims to investigate the association between two polymorphisms, rs12603708 and rs3751987, and SARS-CoV-2 susceptibility, disease severity, and humoral immune responses in a Moroccan population.

MATERIALS AND METHODS

A total of 303 unvaccinated COVID-19 patients (151 severe cases and 152 asymptomatic/moderate cases) and 150 individuals from a SARS-CoV-2-negative group were included in the analysis. Genotyping was performed using TaqMan SNP assays. SARS-CoV-2 antibodies targeting the nucleocapsid protein and IgG antibodies specific to the receptor-binding domain (RBD) were quantified using chemiluminescence microparticles immunoassay. Complete blood counts and C-reactive protein levels were evaluated using an automated platform.

RESULTS

Our analysis revealed that the A/A genotype of rs12603708 significantly increased the risk of SARS-CoV-2 infection in both codominant (p = 0.0055; OR = 3.74; adjusted p value = 0.022) and recessive (p = 0.0049; OR = 3.17; adjusted p value = 0.022) models, as well as the risk of severe disease (p = 0.014; OR = 3.43; adjusted p value = 0.049). For rs3751987, the G/G genotype was linked to higher susceptibility to infection (p = 0.0011; OR = 2.91; adjusted p value = 0.008), while the G/A genotype appeared protective (p = 0.0007; OR = 0.45; adjusted p value = 0.008). No association was found between rs3751987 and disease severity. Analysis of IgG anti-N and anti-RBD levels revealed no significant associations with either polymorphism (p > 0.05).

CONCLUSION

These findings highlight the role of TNFRSF13B polymorphisms in SARS-CoV-2 susceptibility and severity, while their impact on humoral immune responses appears limited.

Comprehensive Analysis of Prognostic Alternative Splicing Signatures in Tumor Immune Infiltration in Bladder Cancer

BACKGROUND

Bladder cancer exhibits substantial heterogeneity encompassing genetic expressions and histological features. This heterogeneity is predominantly attributed to alternative splicing (AS) and AS-regulated splicing factors (SFs), which, in turn, influence bladder cancer development, progression, and response to treatment.

OBJECTIVE

This study aimed to explore the immune landscape of aberrant AS in bladder cancer and establish the prognostic signatures for survival prediction.

METHODS

Bladder cancer-related RNA-Seq, transcriptome, and corresponding clinical information were downloaded from The Cancer Genome Atlas (TCGA). Gene set enrichment analysis (GSEA) was used to identify significantly enriched pathways of cancer-related AS events. The underlying interactions among differentially expressed genes (DEGs) and cancer-related AS events were assessed by a protein-protein interaction network. Univariate and multivariate Cox regression analyses were performed to identify crucial prognostic DEGs that co-occurred with cancer-related AS events (DEGAS) for overall survival. The area under the curve (AUC) of receiver operating characteristic (ROC) curves was used to assess the efficiency of the prognostic signatures. The CIBERSORT algorithm was used to explore the abundance of immune infiltrating cells.

RESULTS

A total of 3755 cancer-related AS events and 3110 DEGs in bladder cancer were identified. Among them, 379 DEGs co-occurred with cancer-related AS events (DEGAS), of which 102 DEGAS were associated with 14 dysregulated SFs. GSEA and KEGG analysis showed that cancer-related AS events were predominantly enriched in pathways related to immunity, tumorigenesis, and treatment difficulties of bladder cancer. Multivariate Cox regression analysis identified 8 DEGAS (CABP1, KCNN2, TNFRSF13B, PCDH7, SNRPA1, APOLD1, CX3CL1, and DENND5A) significantly associated with OS, and they were further integrated into the prediction model with good AUCs at 3-year, 5-year and 7-year ROC curves (all>0.7). Immune infiltration analysis revealed the significant enrichment of three immune cell types (B cells naïve, dendritic cells resting, and dendritic cell activated) in high-risk bladder cancer patients.

CONCLUSION

This study not only unveiled comprehensive prognostic signatures of AS events in bladder cancer but also established a robust prognostic model based on survival-related DEGAS. These aberrant AS events, dysregulated SFs, and the identified 8 DEGAS may have significant clinical potential as therapeutic targets for bladder cancer.

Complement C3d enables cell-mediated immunity capable of distinguishing spontaneously transformed from nontransformed cells

Immune surveillance depends in part on the recognition of peptide variants by T cell antigen receptors. Given that both normal B cells and malignant B cells accumulate mutations we chose a murine model of multiple myeloma to test conditions to induce cell-mediated immunity targeting malignant plasma cell (PC) clones but sparing of normal PCs. Revealing a previously unknown function for intracellular C3d, we found that C3d engaged T cell responses against malignant PC in the bone marrow of mice that had developed multiple myeloma spontaneously. Our results show that C3d internalized by cells augments immune surveillance by several mechanisms. In one, C3d induces a master transcription regulator, E2f1, to increase the expression of long noncoding (lnc) RNAs, to generate peptides for MHC-I presentation, and increase MHC-I expression. In another, C3d increases expression of RNAs encoding ribosomal proteins linked to processing of defective ribosomal products that arise from noncanonical translation and known to promote immunosurveillance. Cancer cells are uniquely susceptible to increased expression and presentation of mutant peptides given the extent of protein misfolding and accumulation of somatic mutations. Accordingly, although C3d can be internalized by any cell, C3d preferentially targets malignant clones by evoking specific T cell-mediated immunity and sparing most nontransformed polyclonal B cells and PC with lower mutation loads. Malignant PC deletion was blocked by cyclosporin or by CD8 depletion confirming that endogenous T cells mediated malignant clone clearance. Besides the potential for therapeutic application our results highlight how intracellular C3d modifies cellular metabolism to augment immune surveillance.

Complement C3d enables protective immunity capable of distinguishing spontaneously transformed from non-transformed cells

Immune-surveillance depends in part on the recognition of peptide variants by T cell antigen receptors. Given that both normal B cells and malignant B cells accumulate mutations we chose a murine model of multiple myeloma to test conditions to induce cell-mediated immunity targeting malignant plasma cell (PC) clones but sparing of normal PCs. Revealing a novel function for intracellular C3d, we discovered that C3d engaged T cell responses against malignant plasma cells in the bone marrow of mice that had developed multiple myeloma spontaneously. Our results show that C3d internalized by cells augments immune surveillance by several mechanisms. In one, C3d induces a master transcription regulator, E2f1, to increase the expression of long non-coding (lnc) RNAs, to generate peptides for MHC-I presentation and increase MHC-I expression. In another, C3d increases expression of RNAs encoding ribosomal proteins linked to processing of defective ribosomal products (DRiPs) that arise from non-canonical translation and known to promote immunosurveillance. Cancer cells are uniquely susceptible to increased expression and presentation of mutant peptides given the extent of protein misfolding and accumulation of somatic mutations. Accordingly, although C3d can be internalized by any cell, C3d preferentially targets malignant clones by evoking specific T cell mediated immunity (CMI) and sparing most non-transformed polyclonal B cells and plasma cells with lower mutation loads. Malignant plasma cell deletion was blocked by cyclosporin or by CD8 depletion confirming that endogenous T cells mediated malignant clone clearance. Besides the potential for therapeutic application our results highlight how intracellular C3d modifies cellular metabolism to augment immune surveillance.

One Sentence Summary

We show that intracellular soluble fragment 3d of complement (C3d) induces regression of spontaneous multiple myeloma in mice reducing tumor burden by 10 fold, after 8 weeks. C3d enables cell-mediated immunity to target multiple myeloma clones sparing non-transformed polyclonal B cells and plasma cells with lower mutation loads. We show that C3d increases the expression of ribosomal subunits associated with the translation of defective ribosomal products (DRiPs). C3d also decreases expression of protein arginine methyl transferase (PRMT) 5 which in turn relieves E2f1 repression increasing the expression of Lnc RNAs and derived peptides that evoke anti-tumor cellular immunity. The approach increases MHC-I expression by tumor cells and generates a CMI response that overcomes tumor immune-evasion strategies.

Significance

Tumors are immunogenic in part because of somatic mutations that originate novel peptides that once presented on MHC engage cell-mediated immunity (CMI). However, in spite of the higher mutation load most tumors evade immunity. We discovered that a component of the complement system (C3d) overcomes tumor immune evasion by augmenting expression of ribosomal proteins and lncRNAs linked to the presentation of novel peptides by tumor cells. C3d induced CMI targets cancer cells sparing non transformed cells uncovering a novel function for complement in immune surveillance.

Somatic Cell Fusion in Host Defense and Adaptation

Evidence of fusion of somatic cells has been noted in health and in disease for more than a century. The most obvious but uncertain hallmark has been the presence of multiple nuclei in cells. Although multinucleated cells are found in normal and diseased tissues, the benefit or harm of such cells can be difficult to elucidate. Still more difficult however is the identification of mononuclear cells previously formed by fusion of somatic cells with one or more nuclei disposed. The later process can introduce mutations that promote viral diversification, cancer, and tissue senescence. Less obvious the potential benefits of cell fusion. Recent work in cell biology, immunology, and genomic analysis however makes it possible to postulate benefits and potentially arrive at novel therapeutic agents and approaches that replicate or enhance these benefits.

Accommodation in allogeneic and xenogeneic organ transplantation: Prevalence, impact, and implications for monitoring and for therapeutics

Accommodation refers to acquired resistance of organs or tissues to immune or inflammatory reactions that might otherwise cause severe injury or rejection. As first observed in ABO-incompatible kidney transplants and heterotopic cardiac xenografts, accommodation was identified when organ transplants continued to function despite the presence of anti-graft antibodies and/or other reactants in the blood of recipients. Recent evidence suggests many and perhaps most organ transplants have accommodation, as most recipients mount B cell responses specific for the graft. Wide interest in the impact of graft-specific antibodies on the outcomes of transplants prompts questions about which mechanisms confer protection against such antibodies, how accommodation might be detected and whether and how rejection could be superimposed on accommodation. Xenotransplantation offers a unique opportunity to address these questions because immune responses to xenografts are easily detected and the pathogenic impact of immune responses is so severe. Xenotransplantation also provides a compelling need to apply these and other insights to decrease the intensity and toxicity of immunosuppression that otherwise could limit clinical application.

Beyond Adaptive Alloreactivity: Contribution of Innate B Cells to Allograft Inflammation and Rejection

Innate B cells are a heterogeneous group of cells that function in maintaining homeostatic levels of circulating natural antibodies and being the first line of defense against infections. Innate B-1 cells and marginal zone B cells may relocate to lymphoid follicles and differentiate into cytokine and antibody-secreting cells in T-independent and T-dependent manners. Although marginal zone B cells are widely described in humans, the presence of B-1 cells is more controversial. Here, we review the basic features of the innate B-cell subsets identified in mice and their equivalent in humans, as well as their potential roles in transplantation. We summarize the findings of Cascalho and colleagues on the unexpected protective role of tumor necrosis factor receptor superfamily member 13B in regulating circulating levels of protective natural immunoglobulin M, and the studies by Zorn and colleagues on the potential pathogenic role for polyreactive innate B cells infiltrating allograft explants. Finally, we discuss our studies that took a transcriptomic approach to identify innate B cells infiltrating kidney allografts with antibody-mediated rejection and to demonstrate that local antigens within the allograft together with inflammation may induce a loss of B-cell tolerance.