Characterization of age-associated B cells in early drug-naïve rheumatoid arthritis patients

Correlation of Professional Antigen-Presenting Tbet+CD11c+ B Cells With Bone Destruction in Untreated Rheumatoid Arthritis

OBJECTIVE

Subsets of CD21-/low memory B cells (MBCs), including double-negative (DN, CD27-IgD-) and Tbet+CD11c+ cells, are expanded in chronic inflammatory diseases. In rheumatoid arthritis (RA), CD21-/low MBCs correlate with joint destruction. However, whether this is due to the Tbet+CD11c+ subset, its function and pathogenic contribution to RA are unknown. This study aims to investigate the association between CD21-/lowTbet+CD11c+ MBCs and joint destruction as well as other clinical parameters and to elucidate their functional properties in patients with untreated RA (uRA).

METHODS

Clinical observations were combined with flow cytometry (n = 36) and single-cell RNA sequencing (scRNA-seq) and V(D)J sequencing (n = 4) of peripheral blood (PB) MBCs from patients with uRA. The transcriptome of circulating Tbet+CD11c+ MBCs was compared with scRNA-seq data of synovial B cells. In vitro coculture of Tbet+CD11c+ B cells with T cells was used to assess costimulatory capacity.

RESULTS

CD21-/lowTbet+CD11c+ MBCs in PB correlated with bone destruction but no other clinical parameters analyzed. The Tbet+CD11c+ MBCs have undergone clonal expansion and express somatically mutated V genes. Gene expression analysis of these cells identified a unique signature of more than 150 up-regulated genes associated with antigen presentation functions, including B cell receptor activation and clathrin-mediated antigen internalization; regulation of actin filaments, endosomes, and lysosomes; antigen processing, loading, presentation, and costimulation; a transcriptome mirrored in their synovial tissue counterparts. In vitro, Tbet+CD11c+ B cells induced retinoic acid receptor-related orphan nuclear receptor γT expression in CD4+ T cells, thereby polarizing to Th17 cells, a T cell subset critical for osteoclastogenesis and associated with bone destruction.

CONCLUSION

This study suggests that Tbet+CD11c+ MBCs contribute to the pathogenesis of RA by promoting bone destruction through antigen presentation, T cell activation, and Th17 polarization.

The peculiar features, diversity and impact of citrulline-reactive autoantibodies

Since entering the stage 25 years ago as a highly specific serological biomarker for rheumatoid arthritis, anti-citrullinated protein antibodies (ACPAs) have been a topic of extensive research. This hallmark B cell response arises years before disease onset, displays interpatient autoantigen variability, and is associated with poor clinical outcomes. Technological and scientific advances have revealed broad clonal diversity and intriguing features including high levels of somatic hypermutation, variable-domain N-linked glycosylation, hapten-like peptide interactions, and clone-specific multireactivity to citrullinated, carbamylated and acetylated epitopes. ACPAs have been found in different isotypes and subclasses, in both circulation and tissue, and are secreted by both plasmablasts and long-lived plasma cells. Notably, although some disease-promoting features have been reported, results now demonstrate that certain monoclonal ACPAs therapeutically block arthritis and inflammation in mouse models. A wealth of functional studies using patient-derived polyclonal and monoclonal antibodies have provided evidence for pathogenic and protective effects of ACPAs in the context of arthritis. To understand the roles of ACPAs, one needs to consider their immunological properties by incorporating different facets such as rheumatoid arthritis B cell biology, environmental triggers and chronic antigen exposure. The emerging picture points to a complex role of citrulline-reactive autoantibodies, in which the diversity and dynamics of antibody clones could determine clinical progression and manifestations.

Cartilage destruction in early rheumatoid arthritis patients correlates with CD21-/low double-negative B cells

BACKGROUND

Involvement of B cells in the pathogenesis of rheumatoid arthritis (RA) is supported by the presence of disease-specific autoantibodies and the efficacy of treatment directed against B cells. B cells that express low levels of or lack the B cell receptor (BCR) co-receptor CD21, CD21-/low B cells, have been linked to autoimmune diseases, including RA. In this study, we characterized the CD21+ and CD21-/low B cell subsets in newly diagnosed, early RA (eRA) patients and investigated whether any of the B cell subsets were associated with autoantibody status, disease activity and/or joint destruction.

METHODS

Seventy-six eRA patients and 28 age- and sex-matched healthy donors were recruited. Multiple clinical parameters were assessed, including disease activity and radiographic joint destruction. B cell subsets were analysed in peripheral blood (PB) and synovial fluid (SF) using flow cytometry.

RESULTS

Compared to healthy donors, the eRA patients displayed an elevated frequency of naïve CD21+ B cells in PB. Amongst memory B cells, eRA patients had lower frequencies of the CD21+CD27+ subsets and CD21-/low CD27+IgD+ subset. The only B cell subset found to associate with clinical factors was the CD21-/low double-negative (DN, CD27-IgD-) cell population, linked with the joint space narrowing score, i.e. cartilage destruction. Moreover, in SF from patients with established RA, the CD21-/low DN B cells were expanded and these cells expressed receptor activator of the nuclear factor κB ligand (RANKL).

CONCLUSIONS

Cartilage destruction in eRA patients was associated with an expanded proportion of CD21-/low DN B cells in PB. The subset was also expanded in SF from established RA patients and expressed RANKL. Taken together, our results suggest a role for CD21-/low DN in RA pathogenesis.

Investigation of Pancreatic-beta Cells Role in the Biological Process of Ageing

BACKGROUND

Cellular senescence is associated with the formation and progression of a range of illnesses, including ageing and metabolic disorders such as diabetes mellitus and pancreatic beta cell dysfunction. Ageing and reduced glucose tolerance are interconnected. Often, Diabetes is becoming more common, which is concerning since it raises the risk of a variety of age-dependent disorders such as cardiovascular disease, cancer, Parkinson's disease, stroke, and Alzheimer's disease.

OBJECTIVES

The objectives of this study are to find out the most recent research on how ageing affects the functions of pancreatic beta cells, beta cell mass, beta cell senescence, mitochondrial dysfunction, and hormonal imbalance.

METHODS

Various research and review manuscripts are gathered from various records such as Google Scholar, PubMed, Mendeley, Scopus, Science Open, the Directory of Open Access Journals, and the Education Resources Information Centre, using different terms like "Diabetes, cellular senescence, beta cells, ageing, insulin, glucose".

RESULTS

In this review, we research novel targets in order to discover new strategies to treat diabetes. Abnormal glucose homeostasis and type 2 diabetes mellitus in the elderly may aid in the development of novel medicines to delay or prevent diabetes onset, improve quality of life, and, finally, increase life duration.

CONCLUSION

Aging accelerates beta cell senescence by generating premature cell senescence, which is mostly mediated by high glucose levels. Despite higher plasma glucose levels, hepatic gluconeogenesis accelerates and adipose tissue lipolysis rises, resulting in an increase in free fatty acid levels in the blood and worsening insulin resistance throughout the body.

In-depth immune profiling reveals advanced B- and T-cell differentiation to be associated with Th1-driven immune dysregulation in common variable immunodeficiency

Common variable immunodeficiency (CVID) is an inborn error of immunity characterized by low levels of antibodies. In addition to infections, many patients also suffer from T-helper 1-driven immune dysregulation, which is associated with increased mortality. The aim of this study was to perform in-depth characterization of the T and the B cell compartments in a well-defined cohort of patients affected by CVID and correlate the findings to the level of clinical immune dysregulation. We used mass cytometry, targeted proteomics, flow cytometry and functional assays to delineate the immunological phenotype of 15 CVID-affected patients with different levels of immune dysregulation. Unbiased clustering of T cell mass cytometry data correlated with CVID-related immune dysregulation and plasma protein profiles. Expanded CXCR3+ T-bet-expressing B cells correlated with effector memory CD4+ T cell clusters, and increased plasma levels of CXCR3-ligands. Our findings indicate an interplay between B cells and T cells in CVID-related immune dysregulation and provide a better understanding of the underlying pathological mechanisms.

Genetics of SLE: mechanistic insights from monogenic disease and disease-associated variants

The past few years have provided important insights into the genetic architecture of systemic autoimmunity through aggregation of findings from genome-wide association studies (GWAS) and whole-exome or whole-genome sequencing studies. In the prototypic systemic autoimmune disease systemic lupus erythematosus (SLE), monogenic disease accounts for a small fraction of cases but has been instrumental in the elucidation of disease mechanisms. Defects in the clearance or digestion of extracellular or intracellular DNA or RNA lead to increased sensing of nucleic acids, which can break B cell tolerance and induce the production of type I interferons leading to tissue damage. Current data suggest that multiple GWAS SLE risk alleles act in concert with rare functional variants to promote SLE development. Moreover, introduction of orthologous variant alleles into mice has revealed that pathogenic X-linked dominant and recessive SLE can be caused by novel variants in TLR7 and SAT1, respectively. Such bespoke models of disease help to unravel pathogenic pathways and can be used to test targeted therapies. Cell type-specific expression data revealed that most GWAS SLE risk genes are highly expressed in age-associated B cells (ABCs), which supports the view that ABCs produce lupus autoantibodies and contribute to end-organ damage by persisting in inflamed tissues, including the kidneys. ABCs have thus emerged as key targets of promising precision therapeutics.

Pathogenesis of autoimmune disease

Autoimmune diseases are a diverse group of conditions characterized by aberrant B cell and T cell reactivity to normal constituents of the host. These diseases occur widely and affect individuals of all ages, especially women. Among these diseases, the most prominent immunological manifestation is the production of autoantibodies, which provide valuable biomarkers for diagnosis, classification and disease activity. Although T cells have a key role in pathogenesis, they are technically more difficult to assay. In general, autoimmune disease results from an interplay between a genetic predisposition and environmental factors. Genetic predisposition to autoimmunity is complex and can involve multiple genes that regulate the function of immune cell populations. Less frequently, autoimmunity can result from single-gene mutations that affect key regulatory pathways. Infection seems to be a common trigger for autoimmune disease, although the microbiota can also influence pathogenesis. As shown in seminal studies, patients may express autoantibodies many years before the appearance of clinical or laboratory signs of disease - a period called pre-clinical autoimmunity. Monitoring autoantibody expression in at-risk populations may therefore enable early detection and the initiation of therapy to prevent or attenuate tissue damage. Autoimmunity may not be static, however, and remission can be achieved by some patients treated with current agents.

Age/autoimmunity-associated B cells in inflammatory arthritis: An emerging therapeutic target

Age/autoimmunity-associated B cells (ABCs) are a novel B cell subpopulation with a unique transcriptional signature and cell surface phenotype. They are not sensitive to BCR but rely on TLR7 or TLR9 in the context of T cell-derived cytokines for the differentiation. It has been established that aberrant expansion of ABCs is linked to the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus. Recently, we and other groups have shown that increased ABCs is associated with rheumatoid arthritis (RA) disease activity and have demonstrated their pathogenic role in RA, indicating that targeting specific B cell subsets is a promising strategy for the treatment of inflammatory arthritis. In this review, we summarize the current knowledge of ABCs, focusing on their emerging role in the pathogenesis of inflammatory arthritis. A deep understanding of the biology of ABCs in the context of inflammatory settings in vivo will ultimately contribute to the development of novel targeted therapies for the treatment of inflammatory arthritis.