Age-Associated B Cells (ABCs) in the Prognosis, Diagnosis and Therapy of Systemic Lupus Erythematosus (SLE)

Developing transcriptomic signatures as a biomarker of cellular senescence

Cellular senescence is a cell fate driven by different types of stress, where damaged cells exit from the cell cycle and, in many cases, develop an inflammatory senescence-associated secretory phenotype (SASP). Senescence has often been linked to driving aging and the onset of multiple diseases conferred by the harmful SASP, which disrupts tissue homeostasis and impairs the regular function of many tissues. This phenomenon was first observed in vitro when fibroblasts halted replication after approximately 50 population doublings. In addition to replication-induced senescence, factors such as DNA damage and oncogene activation can induce cellular senescence both in culture and in vivo. Despite their contribution to aging and disease, identifying senescent cells in vivo has been challenging due to their heterogeneity. Although senescent cells can express the cell cycle inhibitors p16Ink4a and/or p21Cip1 and exhibit SA-ß-gal activity and evidence of a DNA damage response, there is no universal biomarker for these cells, regardless of inducer or cell type. Recent studies have analyzed the transcriptomic characteristics of these cells, leading to the identification of signature gene sets like CellAge, SeneQuest, and SenMayo. Advancements in single-cell and spatial RNA sequencing now allow for analyzing senescent cell heterogeneity within the same tissue and the development of machine learning algorithms, e.g., SenPred, SenSig, and SenCID, to discover cellular senescence using RNA sequencing data. Such insights not only deepen our understanding of the genetic pathways driving cellular senescence, but also promote the development of its quantifiable biomarkers. This review summarizes the current knowledge of transcriptomic signatures of cellular senescence and their potential as in vivo biomarkers.

Targeting T-bet expressing B cells for therapeutic interventions in autoimmunity

Apart from serving as a Th1 lineage commitment regulator, transcription factor T-bet is also expressed in other immune cell types and thus orchestrates their functions. In case of B cells, more specifically, T-bet is responsible for their isotype switching to specific IgG sub-classes (IgG2a/c in mice and IgG1/3 in humans). In various autoimmune disorders, such as systemic lupus erythematosus and/or rheumatoid arthritis, subsets of T-bet expressing B cells, known as age-associated B cells (CD19+CD11c+CD21-T-bet+) and/or double-negative B cells (CD19+IgD-CD27-T-bet+), display an expansion and seem to drive disease pathogenesis. According to data, mostly derived from mice models of autoimmunity, the targeting of these specific B-cell populations is capable of ameliorating the general health status of the autoimmune subjects. Here, in this review article, we present a variety of therapeutic approaches for both mice and humans, suffering from an autoimmune disease, and we discuss the effects of each approach on T-bet+ B cells. In general, we highlight the importance of specifically targeting T-bet+ B cells for therapeutic interventions in autoimmunity.

Is systemic lupus erythematosus linked to Immunoglobulin G4 Autoantibodies?

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by a hyperactive immune system with multiple abnormalities in B-cell proliferation, antibody production, T-cell regulation, and immune complex (IC) formation. In humans, Immunoglobulin (Ig) G is found in four subclasses. IgG1-IgG4, which are distinguished by both structural and biological differences. Fab-arm Exchange (FAE), specific biases in the IgG4 response repertoire, and a decreased capacity to induce effector functions mediated by interactions in the fragment crystallizable (Fc) region are just a few of the distinctive characteristics of IgG4. The recent finding of the presence of double-stranded DNA (dsDNA) and antinuclear antibody (ANA)-IgG4 has raised attention to this IgG subclass and its possible role in SLE. IgG4 was previously believed to just have anti-inflammatory effects by inhibiting immune responses, but recent studies have shown that these antibodies can also play a role in the onset and development of some clinical disorders. To consider the clinical effects of IgG4 presence, it is necessary to discuss its characteristics, which could underlie the potential role it can play in SLE. Therefore, this study aimed to comprehensively review the role of IgG4 in SLE to elucidate the collective incidence of high IgG4 levels reported in some SLE patients.

B Cells Dynamic in Aging and the Implications of Nutritional Regulation

Aging negatively affects B cell production, resulting in a decrease in B-1 and B-2 cells and impaired antibody responses. Age-related B cell subsets contribute to inflammation. Investigating age-related alterations in the B-cell pool and developing targeted therapies are crucial for combating autoimmune diseases in the elderly. Additionally, optimal nutrition, including carbohydrates, amino acids, vitamins, and especially lipids, play a vital role in supporting immune function and mitigating the age-related decline in B cell activity. Research on the influence of lipids on B cells shows promise for improving autoimmune diseases. Understanding the aging B-cell pool and considering nutritional interventions can inform strategies for promoting healthy aging and reducing the age-related disease burden.

B-Cell Receptor Repertoire: Recent Advances in Autoimmune Diseases

In the field of contemporary medicine, autoimmune diseases (AIDs) are a prevalent and debilitating group of illnesses. However, they present extensive and profound challenges in terms of etiology, pathogenesis, and treatment. A major reason for this is the elusive pathophysiological mechanisms driving disease onset. Increasing evidence suggests the indispensable role of B cells in the pathogenesis of autoimmune diseases. Interestingly, B-cell receptor (BCR) repertoires in autoimmune diseases display a distinct skewing that can provide insights into disease pathogenesis. Over the past few years, advances in high-throughput sequencing have provided powerful tools for analyzing B-cell repertoire to understand the mechanisms during the period of B-cell immune response. In this paper, we have provided an overview of the mechanisms and analytical methods for generating BCR repertoire diversity and summarize the latest research progress on BCR repertoire in autoimmune diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), primary Sjögren's syndrome (pSS), multiple sclerosis (MS), and type 1 diabetes (T1D). Overall, B-cell repertoire analysis is a potent tool to understand the involvement of B cells in autoimmune diseases, facilitating the creation of innovative therapeutic strategies targeting specific B-cell clones or subsets.

Autoimmune Responses and Therapeutic Interventions for Systemic Lupus Erythematosus: A Comprehensive Review

Systemic Lupus Erythematosus (SLE) or Lupus is a multifactorial autoimmune disease of multiorgan malfunctioning of extremely heterogeneous and unclear etiology that affects multiple organs and physiological systems. Some racial groups and women of childbearing age are more susceptible to SLE pathogenesis. Impressive progress has been made towards a better understanding of different immune components contributing to SLE pathogenesis. Recent investigations have uncovered the detailed mechanisms of inflammatory responses and organ damage. Various environmental factors, pathogens, and toxicants, including ultraviolet light, drugs, viral pathogens, gut microbiome metabolites, and sex hormones trigger the onset of SLE pathogenesis in genetically susceptible individuals and result in the disruption of immune homeostasis of cytokines, macrophages, T cells, and B cells. Diagnosis and clinical investigations of SLE remain challenging due to its clinical heterogeneity and hitherto only a few approved antimalarials, glucocorticoids, immunosuppressants, and some nonsteroidal anti-inflammatory drugs (NSAIDs) are available for treatment. However, the adverse effects of renal and neuropsychiatric lupus and late diagnosis make therapy challenging. Additionally, SLE is also linked to an increased risk of cardiovascular diseases due to inflammatory responses and the risk of infection from immunosuppressive treatment. Due to the diversity of symptoms and treatment-resistant diseases, SLE management remains a challenging issue. Nevertheless, the use of next-generation therapeutics with stem cell and gene therapy may bring better outcomes to SLE treatment in the future. This review highlights the autoimmune responses as well as potential therapeutic interventions for SLE particularly focusing on the recent therapeutic advancements and challenges.

Increase in Double Negative B Lymphocytes in Patients with Systemic Lupus Erythematosus in Remission and Their Correlation with Early Differentiated T Lymphocyte Subpopulations

B and T lymphocytes demonstrate important alterations in patients with systemic lupus erythematous (SLE), with a significant upregulation of double negative (DN) B cells. The aim of this study was to evaluate the correlation of T cell immunity changes with the distinct B-cell-pattern SLE. In the present study, flow cytometry was performed in 30 patients in remission of SLE and 31 healthy controls to detect DN B cells (CD19+IgD-CD27-) and a wide range of T lymphocyte subpopulations based on the presence of CD45RA, CCR7, CD31, CD28, and CD57, defined as naive, memory, and advanced differentiated/senescent T cells. Both B and T lymphocytes were significantly reduced in SLE patients. However, the percentage of DN B cells were increased compared to HC (12.9 (2.3-74.2) vs. 8 (1.7-35), p = 0.04). The distribution of CD4 and CD8 lymphocytes demonstrated a shift to advanced differentiated subsets. The population of DN B cells had a significant positive correlation with most of the early differentiated T lymphocytes, CD4CD31+, CD4CD45RA+CD28+, CD4CD45RA+CD57-, CD4CD45RA-CD57-, CD4CD28+CD57-, CD4CD28+CD57+, CD4 CM, CD8 CD31+, CD8 NAÏVE, CD8CD45RA-CD57-, CD8CD28+CD57-, and CD8CD28+CD57+. Multiple regression analysis revealed CD4CD31+, CD8CD45RA-CD57-, and CD8CD28+CD57- cells as independent parameters contributing to DN B cells, with adjusted R2 = 0.534 and p < 0.0001. The predominance of DN B cells in patients with SLE is closely associated with early differentiated T lymphocyte subsets, indicating a potential causality role of DN B cells in T lymphocyte activation.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Inflammation and immunomodulation in central nervous system injury - B cells as a novel therapeutic opportunity

Acute injury to the central nervous system (CNS) remains a complex and challenging clinical need. CNS injury initiates a dynamic neuroinflammatory response, mediated by both resident and infiltrating immune cells. Following the primary injury, dysregulated inflammatory cascades have been implicated in sustaining a pro-inflammatory microenvironment, driving secondary neurodegeneration and the development of lasting neurological dysfunction. Due to the multifaceted nature of CNS injury, clinically effective therapies for conditions such as traumatic brain injury (TBI), spinal cord injury (SCI), and stroke have proven challenging to develop. No therapeutics that adequately address the chronic inflammatory component of secondary CNS injury are currently available. Recently, B lymphocytes have gained increasing appreciation for their role in maintaining immune homeostasis and regulating inflammatory responses in the context of tissue injury. Here we review the neuroinflammatory response to CNS injury with particular focus on the underexplored role of B cells and summarize recent results on the use of purified B lymphocytes as a novel immunomodulatory therapeutic for tissue injury, particularly in the CNS.

Single-cell transcriptomics reveals cell type-specific immune regulation associated with anti-NMDA receptor encephalitis in humans

Introduction

Anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDARE) is a rare autoimmune disease, and the peripheral immune characteristics associated with anti-NMDARE antibodies remain unclear.

Methods

Herein, we characterized peripheral blood mononuclear cells from patients with anti-NMDARE and healthy individuals by single-cell RNA sequencing (scRNA-seq).

Results

The transcriptional profiles of 129,217 cells were assessed, and 21 major cell clusters were identified. B-cell activation and differentiation, plasma cell expansion, and excessive inflammatory responses in innate immunity were all identified. Patients with anti-NMDARE showed higher expression levels of CXCL8, IL1B, IL6, TNF, TNFSF13, TNFSF13B, and NLRP3. We observed that anti-NMDARE patients in the acute phase expressed high levels of DC_CCR7 in human myeloid cells. Moreover, we observed that anti-NMDARE effects include oligoclonal expansions in response to immunizing agents. Strong humoral immunity and positive regulation of lymphocyte activation were observed in acute stage anti-NMDARE patients.

Discussion

This high-dimensional single-cell profiling of the peripheral immune microenvironment suggests that potential mechanisms are involved in the pathogenesis and recovery of anti-NMDAREs.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

CD11c+ T-bet+ CD21hi B Cells Are Negatively Associated With Renal Impairment in Systemic Lupus Erythematosus and Act as a Marker for Nephritis Remission

Lupus nephritis (LN) is one of the most common manifestations of systemic lupus erythematosus (SLE), characterized by abnormal B cell activation and differentiation to memory or plasma effector cells. However, the role of these cells in the pathogenesis of LN is not fully understood, as well as the effect of induction therapy on B cell subsets, possibly associated with this manifestation, like aged-associated B cells (ABCs). Consequently, we analyzed the molecules defining the ABCs subpopulation (CD11c, T-bet, and CD21) through flow cytometry of blood samples from patients with lupus presenting or not LN, following up a small sub-cohort after six months of induction therapy. The frequency of ABCs resulted higher in LN patients compared to healthy subjects. Unexpectedly, we identified a robust reduction of a CD21^hi subset that was almost specific to LN patients. Moreover, several clinical and laboratory lupus features showed strong and significant correlations with this undefined B cell subpopulation. Finally, it was observed that the induction therapy affected not only the frequencies of ABCs and CD21^hi subsets but also the phenotype of the CD21^hi subset that expressed a higher density of CXCR5. Collectively, our results suggest that ABCs, and more importantly the CD21^hi subset, may work to assess therapeutic response since the reduced frequency of CD21^hi cells could be associated with the onset of LN.

Involvement of age-associated B cells in EBV-triggered autoimmunity

Abstract

EBV infection has long been suspected to play a role in the development of autoimmune diseases. Interestingly, a recently published study has provided the strongest evidence to date that EBV is truly a trigger for multiple sclerosis, a well known inflammatory and neurodegenerative autoimmune disorder. Taking into account the data derived from mice models of autoimmune diseases that were also infected with a murine analog of EBV, in this commentary, we highlight the involvement of age-associated B cells, a B cell population defined as CD19⁺CD11c⁺CD21⁻T-bet⁺, in the process of EBV-triggered autoimmunity. Of note, the aforementioned B cell subset expands continuously with age in healthy individuals, whereas displays a premature strong accumulation in cases of autoimmune diseases. These cells contribute to autoimmune disease pathogenesis via a variety of functions, such as the production of autoantibodies and/or the formation of spontaneous germinal centers. Latent form of EBV seems to modify these B cells, so as to function pathogenically in cases of autoimmunity. Targeting of ABCs, as well as the elimination of EBV, may both be potential treatments for autoimmunity.

Highlights

Latent form of EBV potentially triggers autoimmune diseases

ABCs expand in autoimmunity and contribute to disease pathogenesis

EBV modifies ABCs, so as to function pathogenically in autoimmune diseases

Apart from EBV elimination, targeting of ABCs may also bring therapeutic benefits to autoimmune patients

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Double Negative (DN) B cells: A connecting bridge between rheumatic diseases and COVID-19?

Double Negative (DN) B cells constitute a B cell population that lacks expression of immunoglobulin D and CD27 memory marker. These cells expand in elderly healthy individuals, but also accumulate prematurely in autoimmune and infectious diseases.

COVID-19 is a pandemic infectious disease caused by SARS-CoV-2, a coronavirus that was first observed in Wuhan, China in December 2019. In its more severe cases, COVID-19 causes severe pneumonia and acute respiratory syndrome with high morbidity and mortality.

Recent studies have revealed that the extrafollicular DN2 B cell subset, previously described in lupus patients, does also expand in severe and/or critical groups of COVID-19 patients. These DN2 cells correlate with disease severity and laboratory parameters of inflammation. However, their exact role and function in COVID-19 require to be further investigated.

In this review, we highlight the DN immune responses in both rheumatic diseases and COVID-19, and we point out the importance of clarifying DN’s role in the immunopathology of the aforementioned infection, as it could probably enable better management of rheumatic diseases during the pandemic. Of note, the symptomatology of COVID-19, as well as the potential outcome of death, have given rise to a worldwide concern and scare of exposition to SARS-CoV-2, especially among the rheumatological patients who believe to be at higher risk due to their immunological background and the immunosuppressive therapies. Nevertheless, there is no convincing evidence so far that these patients are truly at higher risk than others.

Immunopathology and Immunosenescence, the Immunological Key Words of Severe COVID-19. Is There a Role for Stem Cell Transplantation?

The outcomes of Coronavirus disease-2019 (COVID-19) vary depending on the age, health status and sex of an individual, ranging from asymptomatic to lethal. From an immunologic viewpoint, the final severe lung damage observed in COVID-19 should be caused by cytokine storm, driven mainly by interleukin-6 and other pro-inflammatory cytokines. However, which immunopathogenic status precedes this "cytokine storm" and why the male older population is more severely affected, are currently unanswered questions. The aging of the immune system, i.e., immunosenescence, closely associated with a low-grade inflammatory status called "inflammageing," should play a key role. The remodeling of both innate and adaptive immune response observed with aging can partly explain the age gradient in severity and mortality of COVID-19. This review discusses how aging impacts the immune response to the virus, focusing on possible strategies to rejuvenate the immune system with stem cell-based therapies. Indeed, due to immunomodulatory and anti-inflammatory properties, multipotent mesenchymal stem cells (MSCs) are a worth-considering option against COVID-19 adverse outcomes.

Effects of Tocilizumab Therapy on Circulating B Cells and T Helper Cells in Patients With Neuromyelitis Optica Spectrum Disorder

Tocilizumab, a humanized anti-IL-6 receptor monoclonal antibody, showed its therapeutic efficacy on neuromyelitis optica spectrum disorder (NMOSD). To assess the immunological effects of this drug on B cells, follicular T helper (Tfh) cells, and peripheral T helper (Tph) cells in patients with NMOSD, peripheral B cell and Tfh cell phenotypes were evaluated in 26 patients with NMOSD before and after tocilizumab treatment by nine-color flow cytometry, as well as the expression of costimulatory and co-inhibitory molecules on B cells. Results showed that the frequency of CD27⁺IgD⁻ switched memory B cells, CD27^-IgD^- double-negative B cells, and CD27^highCD38^high antibody-secreting cells was increased in patients with NMOSD. Tocilizumab treatment led to a significant shift of B cells to naïve B cells from memory B cells after 3 months. Three markers on B cells associated with T-cell activation (i.e., CD86 CD69, and HLA-DR) were downregulated after tocilizumab treatment. The frequencies of total Tfh and Tph cells were decreased, whereas that of follicular regulatory T cells tended to increase. Intrinsic increased PD-L1 and PD-L2 expression was characteristic of B cells in patients with NMOSD. Tocilizumab selectively restored PD-L1 on B-cell subsets. These results provided evidence that tocilizumab enhanced B- and T-cell homoeostasis by regulating B-cell differentiation and inhibiting lymphocyte activation in patients with NMOSD.

Older adults: panoramic view on the COVID-19 vaccination

In December 2020, COVID-19 vaccination started in many countries, with which the world community hopes to stop the further spread of the current pandemic. More than 90% of sick and deceased patients belong to the category of older adults (65 years and older). This category of the population is most vulnerable to infectious diseases, so vaccination is the most effective preventive strategy, the need for which for older adults is indisputable. Here we briefly summarize information about age-related changes in the immune system and present current data on their impact on the formation of the immune response to vaccination. Older age is accompanied by the process of biological aging accompanied by involution of the immune system with increased susceptibility to infections and a decrease in the effect of immunization. Therefore, in the ongoing mass COVID-19 vaccination, the older adults are a growing public health concern. The authors provide an overview of the various types of COVID-19 vaccines approved for mass immunization of the population by the end of 2020, including older adults, as well as an overview of strategies and platforms to improve the effectiveness of vaccination of this population. In the final part, the authors propose for discussion a system for assessing the safety and monitoring the effectiveness of COVID-19 vaccines for the older adults.