B cell resistance to Fas-mediated apoptosis contributes to their ineffective control by regulatory T cells in rheumatoid arthritis

Functional implications of rs9373441 with FOXP3+Treg and Tr1 for the clinical effectiveness of csDMARDs in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by a deficiency in regulatory T cells (Treg), which play a crucial role in immune regulation. While conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) are widely used, there remains a challenge as efficacy varies among patients. In this genome-wide association study (GWAS) involving 410 RA patients, rs9373441 emerged as the most significantly linked single-nucleotide polymorphism (SNP) to csDMARDs response. This non-coding variant functions as a cis-acting regulatory element within the UTRN gene, which is associated with cortical erosion and osteoporosis. Particularly, individuals with the TT allele at rs9373441 exhibited a more favorable response, characterized by a significant increase in FOXP3 + Treg and Type 1 regulatory T cells (Tr1) (p = 0.04, 0.02) and a decrease in Effector T helper cells (Effector Th) (p = 0.03). The GATA3-GCM2-PTH and GATA3-FOXO1-FOXP3 pathways were implicated. RNA-sequencing (RNA-seq) analysis revealed increased expression levels of UTRN, PTH2R, FOXO1, and FOXO3 in good and moderate responders (p = 0.01, 0.03, 0.0005, and 0.02). Notably, the change in FOXP3 + Treg and Tr1 was positively correlated with UTRN expression (both p = 0.03). These findings underscore the critical link between rs9373441 and the response to csDMARDs, empowering clinicians to tailor treatments for enhanced outcomes in patients with RA.

The association between neutrophil-to-lymphocyte ratio and disease activity in rheumatoid arthritis

The inflammatory response is responsible for the promotion of pannus development over the joint, which is the primary factor in joint injury in rheumatoid arthritis (RA). More in-depth investigations have been conducted in recent years leading to a greater understanding of RA. Yet, it's difficult to gauge inflammation levels in RA patients. Some people who have RA do not exhibit normal symptoms, which makes it more challenging to make a diagnosis. Typical RA evaluations are subject to a few restrictions. Earlier research demonstrated that some patients continued to experience the progression of bone and joint degeneration even while in clinical remission. This progression was attributed to ongoing synovial inflammation. As a result, performing a precise evaluation of the level of inflammation is of the utmost importance. The neutrophil-to-lymphocyte ratio (NLR) has consistently been one of the most interesting novel non-specific inflammatory indicators. It is a reflection of the equilibrium between lymphocytes and neutrophils, which are inflammatory regulators and inflammatory activators, respectively. A higher NLR is linked to more severe levels of imbalance and inflammation. The aim of this study was to depict the role of NLR in RA progression and to show if NLR could predict the response to disease-modifying antirheumatic drugs (DMARDs) therapy in RA.

CD8+ Regulatory T Cell Deficiency in Elderly-Onset Rheumatoid Arthritis

Elderly-onset rheumatoid arthritis (EORA) is associated with higher disease activity and accelerated joint destruction compared with young-onset RA (YORA). However, the underlying immunological mechanism remains unclear. Regulatory T cells (Tregs) are an immunosuppressive T cell subset, and CD4+ Tregs are deficient and/or dysfunctional in RA; however, CD8+ Tregs have not been fully examined in RA. Here, we aimed to determine the role of CD8+ Tregs, particularly in EORA. A total of 40 patients (EORA, n = 17; YORA, n = 23) were cross-sectionally enrolled. Current disease activity and treatment were comparable between the two groups; however, levels of multiple cytokines, including IL-1β, TNFα, interferon (IFN)-γ, IL-2, and IL-10, were significantly increased in EORA. The number of CD4+ Tregs did not differ between the groups (p = 0.37), but those of CD8+ Tregs were significantly decreased in EORA (p = 0.0033). The number of CD8+ Tregs were inversely correlated with plasma matrix metalloprotease (MMP)-3 levels (r = −0.3331, p = 0.036). Our study results revealed an intrinsic deficiency of CD8+ Tregs in patients with EORA, which leaves synovitis unchecked with excessive MMP-3 release. A therapeutic approach to restore CD8+ Tregs may provide a new avenue for the treatment of EORA.

Role of T Cells in the Pathogenesis of Rheumatoid Arthritis: Focus on Immunometabolism Dysfunctions

Evidence demonstrated that metabolic-associated T cell abnormalities could be detected in the early stage of RA development. In this context, molecular evaluations have revealed changes in metabolic pathways, leading to the aggressive phenotype of RA T cells. A growing list of genes is downregulated or upregulated in RA T cells, and most of these genes with abnormal expression fall into the category of metabolic pathways. It has been shown that RA T cells shunt glucose towards the pentose phosphate pathway (PPP), which is associated with a high level of nicotinamide adenine dinucleotide phosphate (NADPH) and intermediate molecules. An increased level of NADPH inhibits ATM activation and thereby increases the proliferation capabilities of the RA T cells. Defects in the DNA repair nuclease MRE11A cause failures in repairing mitochondrial DNA, resulting in inhibiting the fatty acid oxidation pathway and further elevated cytoplasmic lipid droplets. Accumulated lipid droplets employ to generate lipid membranes for the cell building program and are also used to form the front-end membrane ruffles that are accomplices with invasive phenotypes of RA T cells. Metabolic pathway involvement in RA pathogenesis expands the pathogenic concept of the disease beyond the common view of autoimmunity triggered by autoantigen recognition. Increased knowledge about metabolic pathways' implications in RA pathogenesis paves the way to understand better the environment/gene interactions and host/microbiota interactions and introduce potential therapeutic approaches. This review summarized emerging data about the roles of T cells in RA pathogenesis with a focus on immunometabolism dysfunctions and how these metabolic alterations can affect the disease process.

B cell-T cell interplay in immune regulation: A focus on follicular regulatory T and regulatory B cell functions

B cells are the core components of humoral immunity. A mature B cell can serve in multiple capacities, including antibody production, antigen presentation, and regulatory functions. Forkhead box P3 (FoxP3)-expressing regulatory T cells (Tregs) are key players in sustaining immune tolerance and keeping inflammation in check. Mounting evidence suggests complex communications between B cells and Tregs. In this review, we summarize the yin-yang regulatory relationships between B cells and Tregs mainly from the perspectives of T follicular regulatory (Tfr) cells and regulatory B cells (Bregs). We discuss the regulatory effects of Tfr cells on B cell proliferation and the germinal center response. Additionally, we review the indispensable role of B cells in ensuring homeostatic Treg survival and describe the function of Bregs in promoting Treg responses. Finally, we introduce a new subset of Tregs, termed Treg-of-B cells, which are induced by B cells, lake the expression of FoxP3 but still own immunomodulatory effects. In this article, we also enumerate a sequence of research from clinical patients and experimental models to clarify the role of Tfr cells in germinal centers and the role of convention B cells and Bregs to Tregs in the context of different diseases. This review offers an updated overview of immunoregulatory networks and unveils potential targets for therapeutic interventions against cancer, autoimmune diseases and allograft rejection.

Apoptosis, Autophagy, NETosis, Necroptosis, and Pyroptosis Mediated Programmed Cell Death as Targets for Innovative Therapy in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that can lead to clinical manifestations of systemic diseases. Its leading features include chronic synovial inflammation and degeneration of the bones and joints. In the past decades, multiple susceptibilities for rheumatoid arthritis have been identified along with the development of a remarkable variety of drugs for its treatment; which include analgesics, glucocorticoids, nonsteroidal anti-inflammatory medications (NSAIDs), disease-modifying anti-rheumatic drugs (DMARDs), and biologic response modifiers (bDMARDs). Despite the existence of many clinical treatment options, the prognosis of some patients remains poor due to complex mechanism of the disease. Programmed cell death (PCD) has been extensively studied and ascertained to be one of the essential pathological mechanisms of RA. Its dysregulation in various associated cell types contributes to the development of RA. In this review, we summarize the role of apoptosis, cell death-associated neutrophil extracellular trap formation, necroptosis, pyroptosis, and autophagy in the pathophysiology of RA to provide a theoretical reference and insightful direction to the discovery and development of novel therapeutic targets for RA.

Dysfunctions, Molecular Mechanisms, and Therapeutic Strategies of Regulatory T Cells in Rheumatoid Arthritis

Regulatory T cells (Tregs) represent a distinct subpopulation of CD4⁺ T lymphocytes that promote immune tolerance and maintain immune system homeostasis. The dysfunction of Tregs is tightly associated with rheumatoid arthritis (RA). Although the complex pathogenic processes of RA remain unclear, studies on Tregs in RA have achieved substantial progress not only in fundamental research but also in clinical application. This review discusses the current knowledge of the characterizations, functions, and molecular mechanisms of Tregs in the pathogenesis of RA, and potential therapies for these disorders are also involved.

Regulatory T Cells: Concept, Classification, Phenotype, and Biological Characteristics

Regulatory T cells (Treg) play an indispensable role in maintaining the body's immune nonresponse to self-antigens and suppressing the body's unwarranted and potentially harmful immune responses. Their absence, reduction, dysfunction, transformation, and instability can lead to numerous autoimmune diseases. There are several distinct subtypes of the Treg cells, although they share certain biological characteristics and have unique phenotypes with different regulatory functions, as well as mechanistic abilities. In this book chapter, we introduce the latest advances in Treg cell subtypes pertaining to classification, phenotype, biological characteristics, and mechanisms. We also highlight the relationship between Treg cells and various diseases, including autoimmune, infectious, as well as tumors and organ transplants.

Treg cells in health and autoimmune diseases: New insights from single cell analysis

Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) or Rheumatoid Arthritis (RA) are characterized by the breakdown of immunological tolerance. Defects of regulatory T cells have been described among the various mechanisms, that are important for the development of autoimmune diseases, due to their critical role as regulators of peripheral immune tolerance and homeostasis. Initially T suppressor cells have been described as one population of peripheral T cells. Based on new technological advances a new understanding of the heterogeneity of different Treg cell populations in the lymphoid and non-lymphoid tissue has evolved over the last years. While initially Foxp3 has been defined as the main master regulator of Treg cells, we have learned that Treg cells from various tissue can be identified by a specific transcriptomic and epigenetic signature. Epigenetic mechanisms allow Treg cell stability, but we have also learned that certain Treg subsets are plastic and can under specific circumstances even enhance autoimmunity and inflammatory processes. Quantitative and functional defects of Treg cells have been observed in a variety of autoimmune diseases. Due to our understanding of the nature of this cell population, Treg cells have been a target of new Treg based therapies, such as low-dose IL-2. In addition, ongoing clinical trials aim to test safety and efficacy of transferred, in vitro expanded Treg cells in patients with autoimmune diseases and transplant patients.

Treg cells in autoimmunity: from identification to Treg-based therapies

Regulatory (Treg) cells are key regulators of inflammation and important for immune tolerance and homeostasis. A major progress has been made in the identification and classification of Treg cells. Due to technological advances, we have gained deep insights in the epigenetic regulation of Treg cells. The use of fate reporter mice allowed addressing the functional consequences of loss of Foxp3 expression. Depending on the environment Treg cells gain effector functions upon loss of Foxp3 expression. However, the traditional view that Treg cells become necessarily pathogenic by gaining effector functions was challenged by recent findings and supports the notion of Treg cell lineage plasticity. Treg cell stability is also a major issue for Treg cell therapies. Clinical trials are designed to use polyclonal Treg cells as therapeutic tools. Here, we summarize the role of Treg cells in selected autoimmune diseases and recent advances in the field of Treg targeted therapies.

Autoimmune rheumatic disease IgG has differential effects upon neutrophil integrin activation that is modulated by the endothelium

The importance of neutrophils in the pathogenesis of autoimmune rheumatic diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), is increasingly recognised. Generation of reactive oxygen species (ROS) and release of neutrophil extracellular traps (NETs) by activated neutrophils are both thought to contribute to pathology; although the underlying mechanisms, particularly the effects of IgG autoantibodies upon neutrophil function, are not fully understood. Therefore, we determined whether purified IgG from patients with SLE or RA have differential effects upon neutrophil activation and function. We found that SLE- and RA-IgG both bound human neutrophils but differentially regulated neutrophil function. RA- and SLE-IgG both increased PMA-induced β₁ integrin-mediated adhesion to fibronectin, whilst only SLE-IgG enhanced α_Mβ₂ integrin-mediated adhesion to fibrinogen. Interestingly, only SLE-IgG modulated neutrophil adhesion to endothelial cells. Both SLE- and RA-IgG increased ROS generation and DNA externalisation by unstimulated neutrophils. Only SLE-IgG however, drove DNA externalisation following neutrophil activation. Co-culture of neutrophils with resting endothelium prevented IgG-mediated increase of extracellular DNA, but this inhibition was overcome for SLE-IgG when the endothelium was stimulated with TNF-α. This differential pattern of neutrophil activation has implications for understanding SLE and RA pathogenesis and may highlight avenues for development of novel therapeutic strategies.

Pathogenic Role of Immune Cells in Rheumatoid Arthritis: Implications in Clinical Treatment and Biomarker Development

Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic, inflammatory disorder that affects synovial joints, both small and large joints, in a symmetric pattern. This disorder usually does not directly cause death but significantly reduces the quality of life and life expectancy of patients if left untreated. There is no cure for RA but, patients are usually on long-term disease modifying anti-rheumatic drugs (DMARDs) to suppress the joint inflammation, to minimize joint damage, to preserve joint function, and to keep the disease in remission. RA is strongly associated with various immune cells and each of the cell type contributes differently to the disease pathogenesis. Several types of immunomodulatory molecules mainly cytokines secreted from immune cells mediate pathogenesis of RA, hence complicating the disease treatment and management. There are various treatments for RA depending on the severity of the disease and more importantly, the patient’s response towards the given drugs. Early diagnosis of RA and treatment with (DMARDs) are known to significantly improve the treatment outcome of patients. Sensitive biomarkers are crucial in early detection of disease as well as to monitor the disease activity and progress. This review aims to discuss the pathogenic role of various immune cells and immunological molecules in RA. This review also highlights the importance of understanding the immune cells in treating RA and in exploring novel biomarkers.

B Lymphocytes in Rheumatoid Arthritis and the Effects of Anti-TNF-α Agents on B Lymphocytes: A Review of the Literature

PURPOSE

The aim of this article was to review published research related to B lymphocytes in rheumatoid arthritis, their role in the pathogenesis of the disease, the effects of tumor necrosis factor (TNF)-α inhibitors on B lymphocytes, the risk for infection, and responses to vaccines.

METHODS

A PubMed search was conducted to review recent advances related to B lymphocytes and the effects of anti-TNF-α on B lymphocytes in rheumatoid arthritis.

FINDINGS

B lymphocytes play an important role in the pathogenesis of rheumatoid arthritis. In this review, we summarize the major mechanisms by which B lymphocytes play a pathologic role in the development and propagation of the disease, as B lymphocytes are recruited to the synovial fluid, where they contribute to local inflammation through the secretion of pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) and present antigens to T cells. We discuss the effects of TNF-α, either direct or indirect, on B lymphocytes expressing receptors for this cytokine. We also show that total B-cell numbers have been reported to be reduced in the blood of patients with rheumatoid arthritis versus healthy controls, but are significantly increased up to normal levels in patients undergoing anti-TNF-α therapy. As for B-cell subsets, controversial results have been reported, with studies showing decreased frequencies of total memory B cells (and memory subsets) and others showing no differences in patients versus healthy controls. Studies investigating the effects of anti-TNF-α therapy have also given controversial results, with therapy found to increase (or not) the frequency of memory B lymphocytes, in patients with rheumatoid arthritis versus healthy controls. Those highly variable results could have been due to differences in patient characteristics and limited numbers of subjects. Finally, we summarize the effects of blocking TNF-α with anti-TNF-α agents on possible infections that patients with rheumatoid arthritis may contract, as well as on responses to vaccination.

IMPLICATIONS

B lymphocytes play a significant role in the pathogenesis of rheumatoid arthritis, and B cell-depletion therapy has a major effect on the course of the disease. The advances in treatment of rheumatoid arthritis include the development of targeted therapies. Anti-TNF-α therapies are widely used despite potentially serious adverse events. The data on the effects of anti-TNF-α therapies on B lymphocytes are limited and conflicting. There is a need for larger studies to better understand the effects of newly discovered therapies on the different cells of the immune system.

Functional Defects of Treg Cells: New Targets in Rheumatic Diseases, Including Ankylosing Spondylitis

PURPOSE OF REVIEW

This study aims to review the advances of Treg cell biology, the functional defects of Treg cells, and the potential strategies for the experimental, preclinical or clinical application of Treg cell therapy in the context of autoimmune/immune-mediated rheumatic diseases.

RECENT FINDINGS

CD4⁺CD25⁺ regulatory T (Treg) cells are a phenotypically and functionally heterogeneous subset of lymphocytes that prevent a variety of autoimmune diseases. As in many autoimmune diseases, the functional defects of Treg cells are supposed to play relevant roles in the pathogenesis and development of systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, and other autoimmune/immune-mediated rheumatic diseases. Consequently, manipulation and modulation of Treg cells represent a potent strategy for therapeutic benefit in many such diseases. A further understanding of the functional defects of Treg cells in rheumatic diseases will contribute to find new targets and therapies in rheumatic diseases, including ankylosing spondylitis.

Efficacy and safety of tregalizumab in patients with rheumatoid arthritis and an inadequate response to methotrexate: results of a phase IIb, randomised, placebo-controlled trial

OBJECTIVE

To evaluate the efficacy, biological activity and safety of tregalizumab in patients with active rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX).

METHODS

321 patients were randomised (1:1:1:1) to placebo or tregalizumab 25, 100 or 200 mg once-weekly subcutaneously in addition to MTX treatment. Responders at week 12 continued the same treatment, and non-responders at week 12 were escalated to the next higher tregalizumab dose level or re-randomised from placebo to active treatment. After 24 weeks, patients could continue treatment with tregalizumab for 24 weeks (extension phase). The primary endpoint was the American College of Rheumatology 20% improvement criteria (ACR20) response rate at week 12. Safety and biological activity were monitored through week 48.

RESULTS

At week 12, ACR20 response rates were not statistically significantly different between placebo and any of the tregalizumab doses. Tregalizumab injections were well tolerated; most adverse events were mild to moderate and comparable among treatment and placebo groups. Biological activity was shown by dose-dependent CD4 downmodulation.

CONCLUSION

Treatment with tregalizumab did not show significant clinical efficacy in patients with active RA compared with placebo but resulted in the expected biological effect on CD4 modulation. Tregalizumab was generally well tolerated, and no new safety findings were identified.

TRIAL REGISTRATION NUMBER

NCT01999192; Results.

Aging, Obesity, and Inflammatory Age-Related Diseases

The increase in the prevalence of obesity represents a worldwide phenomenon in all age groups and is pathologically and genetically correlated with several metabolic and cardiovascular diseases, representing the most frequent age-related diseases. Obesity superimposed on aging drastically increases chronic low-grade inflammation (inflammaging), which is an important link between obesity, insulin resistance, and age-associated diseases. Immune cells of both the innate and the adaptive immune systems infiltrate the adipose tissue (AT) and during obesity induce inflammatory responses associated with metabolic switches and changes in phenotypes and function of immune cell subsets. Obesity poses new health problems especially when it occurs in the context of other diseases, many of them frequently affect elderly subjects. An emerging problem is the decreased proportion of patients with obesity achieving clinical response to therapy. In this review, we will discuss the reciprocal influences of immune cell and AT inflammation in aging and age-associated diseases and the complex relationship of nutrient and energy-sensing homeostatic checkpoints, which contribute to shape the phenotype of the AT. We will specifically examine type-2 diabetes, rheumatoid arthritis, osteoarthritis, cognitive impairment, and dementia, where obesity plays a significant role, also in shaping some clinical aspects.

B-cell phenotype and IgD-CD27- memory B cells are affected by TNF-inhibitors and tocilizumab treatment in rheumatoid arthritis

Background

The use of TNF-inhibitors and/or the IL-6 receptor antagonist, tocilizumab, in rheumatoid arthritis (RA) have pleiotropic effects that also involve circulating B-cells. The main goal of this study was to assess the effect of TNF-inhibitors and tocilizumab on B-cell phenotype and gene expression in RA.

Methods

Blood samples were collected from untreated early RA (ERA) patients, established RA patients under methotrexate treatment, established RA patients before and after treatment with TNF-inhibitors and tocilizumab, and healthy donors. B-cell subpopulations were characterized by flow cytometry and B-cell gene expression was analyzed by real-time PCR on isolated B-cells. Serum levels of BAFF, CXCL13 and sCD23 were determined by ELISA.

Results

The frequency of total CD19+ B cells in circulation was similar between controls and all RA groups, irrespective of treatment, but double negative (DN) IgD-CD27- memory B cells were significantly increased in ERA and established RA when compared to controls. Treatment with TNF-inhibitors and tocilizumab restored the frequency of IgD-CD27- B-cells to normal levels, but did not affect other B cell subpopulations. TACI, CD95, CD5, HLA-DR and TLR9 expression on B-cells significantly increased after treatment with either TNF-inhibitors and/ or tocilizumab, but no significant changes were observed in BAFF-R, BCMA, CD69, CD86, CXCR5, CD23, CD38 and IgM expression on B-cells when comparing baseline with post-treatment follow-ups. Alterations in B-cell gene expression of BAFF-R, TACI, TLR9, FcγRIIB, BCL-2, BLIMP-1 and β2M were found in ERA and established RA patients, but no significant differences were observed after TNF-inhibitors and tocilizumab treatment when comparing baseline and follow-ups. Serum levels of CXCL13, sCD23 and BAFF were not significantly affected by treatment with TNF-inhibitors and tocilizumab.

Conclusions

In RA patients, the use of TNF-inhibitors and/ or tocilizumab treatment affects B-cell phenotype and IgD-CD27- memory B cells in circulation, but not B-cell gene expression levels.

Immunization of BALB/c mice with pigeon IgY induces the production of anti-IgG autoantibodies

The breakdown of immunological tolerance due to the activation of autoreactive B and T cells triggers physiopathological processes. An example of such conditions is the production of IgG autoantibodies specific for the Fc portion of IgG (anti-Fcγ IgG). Previous reports have shown that patients with pigeon-related hypersensitivity pneumonitis exhibit an increase in the serum levels of anti-Fcγ IgG. There is no in vivo model for the study of this condition and the immunological mechanisms of tolerance breakdown associated with sensitization by pigeon antigens are still unknown. In this work, we show that the repeated immunization of BALB/c mice with pigeon IgY during 16-weeks induces the production of anti-Fcγ IgG and keeps their high levels for seven weeks. The late appearance of anti-Fcγ IgG autoantibodies in the plasma is similar to what has been reported in other experimental autoimmune models. With the occurrence of anti-Fcγ IgG, there is a reduction in the proportion of Foxp3 + cells (regulatory T cells, Tregs) within the population of splenic CD4 + CD25 + T cells. Thus, our data showed that the immunization of BALB/c mice with IgY promotes the production of anti-Fcγ IgG along with a decrease in Tregs in the spleen. We propose that immunization of mice with pigeon antigens, like IgY can provide a model to study the immunological mechanisms involved in the development of pigeon-related hypersensitivity pneumonitis.

Foxp3, Regulatory T Cell, and Autoimmune Diseases

Regulatory T cells (Tregs) represent a cell type that promotes immune tolerance to autologous components and maintains immune system homeostasis. The abnormal function of Tregs is relevant to the pathogenesis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and other autoimmune diseases. Therefore, therapeutic modulation of Tregs could be a potent means of treating autoimmune diseases. Human Tregs are diverse, however, and not all of them have immunosuppressive effects. Forkhead box P3 (Foxp3), a pivotal transcription factor of Tregs that is crucial in maintaining Treg immunosuppressive function, can be expressed heterogeneously or unstably across Treg subpopulations. Insights into modulating Treg differentiation on the level of DNA transcription or protein modification may improve the success of Treg modifying immunotherapies. In this review, we will summarize three main prospects: the regulatory mechanism of Foxp3, the influence on Foxp3 and Tregs in autoimmune diseases, then finally, how Tregs can be used to treat autoimmune diseases.

Arthritis models: usefulness and interpretation

Animal models of arthritis are used to better understand pathophysiology of a disease or to seek potential therapeutic targets or strategies. Focusing on models currently used for studying rheumatoid arthritis, we show here in which extent models were invaluable to enlighten different mechanisms such as the role of innate immunity, T and B cells, vessels, or microbiota. Moreover, models were the starting point of in vivo application of cytokine-blocking strategies such as anti-TNF or anti-IL-6 treatments. The most popular models are the different types of collagen-induced arthritis and arthritis in KBN mice. As spontaneous arthritides, human TNF-α transgenic mice are a reliable model. It is mandatory to use animal models in the respect of ethical procedure, particularly regarding the number of animals and the control of pain. Moreover, design of experiments should be of the highest level, animal models of arthritis being dedicated to exploration of well-based novelties, and never used for confirmation or replication of already proven concepts. The best interpretations of data in animal models of arthritis suppose integrated research, including translational studies from animals to humans.

Regulatory T Cells: Molecular and Cellular Basis for Immunoregulation

CD4⁺ regulatory T cells (Tregs) are a highly immune-suppressive subset of CD4⁺ T cells, characterized by expression of the master regulatory transcription factor FOXP3. Tregs are proven to play central roles in the maintenance of self-tolerance in healthy individuals. Tregs are involved in maintaining immune homeostasis: they protect hosts from developing autoimmune diseases and allergy, whereas in malignancies, they promote tumor progression by suppressing anti-tumor immunity. Elucidating factors influencing Treg homeostasis and function have important implications for understanding disease pathogenesis and identifying therapeutic opportunities. Thus, the manipulating Tregs for up- or down-regulation of their suppressive function is a new therapeutic strategy for treating various diseases including autoimmune disorders and cancer. This review will focus on recent advances in how Tregs integrate extracellular and intracellular signals to control their survival and stability. Deeper mechanistic understanding of disease-specific Treg development, maintenance, and function could make disease-specific Treg-targeted therapy more effective, resulting in an increase of efficacy and decrease of side effects related to manipulating Tregs.

The thymus and rheumatology: should we care?

Purpose of review

The purpose of this review is to discuss the mechanisms of central and peripheral tolerance in relation to T-cell mediated autoimmunity in rheumatoid arthritis (RA).

Recent findings

The well established association between major histocompatibility complex class II and RA has led us to understand that T cells, and the adaptive immune response, are important in the pathogenesis of disease. In order for autoimmune disease to develop, there is a breach of tolerance to self antigen and the mechanisms of both central and peripheral tolerance aim to prevent this. Here, we review evidence from mouse models indicating that alterations in T-cell receptor signalling thresholds during thymic selection may be linked to the escape of T cells that mediate autoimmune arthritis. In addition, we summarize the role of dendritic cells and Foxp3+ regulatory T cells in both peripheral and thymic tolerance, and highlight their relevance to what we know about the aetiology of RA.

Summary

Mechanisms of central tolerance in the thymus and peripheral tolerance are in place to control autoreactive T cells and to prevent the development of autoimmune disease. We anticipate that a better understanding of these mechanisms will lead to the development of better, antigen-specific therapeutics to restore tolerance.

Fas Versatile Signaling and Beyond: Pivotal Role of Tyrosine Phosphorylation in Context-Dependent Signaling and Diseases

The Fas/FasL system is known, first and foremost, as a potent apoptosis activator. While its proapoptotic features have been studied extensively, evidence that the Fas/FasL system can elicit non-death signals has also accumulated. These non-death signals can promote survival, proliferation, migration, and invasion of cells. The key molecular mechanism that determines the shift from cell death to non-death signals had remained unclear until the recent identification of the tyrosine phosphorylation in the death domain of Fas as the reversible signaling switch. In this review, we present the connection between the recent findings regarding the control of Fas multi-signals and the context-dependent signaling choices. This information can help explain variable roles of Fas signaling pathway in different pathologies.

Emerging Therapies for Rheumatoid Arthritis

Diverse strategies to develop novel treatments for rheumatoid arthritis which specifically target those patients who do not respond to available medications, including biologics, are currently being explored. New potential therapeutic approaches which may become available as part of standard therapeutic regimens include the propagation of regulatory T cells and-in the future-of regulatory B cells. New biologic disease-modifying antirheumatic drugs (b-DMARDs) against interleukin-17 and -6, granulocyte-macrophage colony-stimulating factor, and complement component 5 are now standard components of clinical treatment programs. In addition, recent data indicate that bispecific monoclonal antibody therapies may be more effective than monoclonal antibody monotherapies. It is also becoming apparent that the use of more toxic b-DMARDs against B cells, a therapeutic strategy already being applied in the treatment of hematological diseases, may also be efficacious for treating B cell-mediated autoimmune diseases. Undoubtedly, more small molecules will be developed in the future, and combination therapies with, for example, kinase inhibitors and b-DMARDs, will most likely be tested. Finally, immunoproteasome inhibitors will become available for patients with B cell-mediated autoimmunities, which are refractory to currently available treatment options. The new and exciting extension of current treatment options for rheumatoid arthritis, biosimilars, will not be discussed in this review as details on these agents are available in recently published reports.

A Recombinant G Protein Plus Cyclosporine A-Based Respiratory Syncytial Virus Vaccine Elicits Humoral and Regulatory T Cell Responses against Infection without Vaccine-Enhanced Disease

Respiratory syncytial virus (RSV) infection can cause severe disease in the lower respiratory tract of infants and older people. Vaccination with a formalin-inactivated RSV vaccine (FI-RSV) and subsequent RSV infection has led to mild to severe pneumonia with two deaths among vaccinees. The vaccine-enhanced disease (VED) was recently demonstrated to be due to an elevated level of Th2 cell responses following loss of regulatory T (Treg) cells from the lungs. To induce high levels of neutralizing Abs and minimize pathogenic T cell responses, we developed a novel strategy of immunizing animals with a recombinant RSV G protein together with cyclosporine A. This novel vaccine induced not only a higher level of neutralizing Abs against RSV infection, but, most importantly, also significantly higher levels of Treg cells that suppressed VED in the lung after RSV infection. The induced responses provided protection against RSV challenge with no sign of pneumonia or bronchitis. Treg cell production of IL-10 was one of the key factors to suppress VED. These finding indicate that G protein plus cyclosporine A could be a promising vaccine against RSV infection in children and older people.

Inhibition of B-cell apoptosis is mediated through increased expression of Bcl-2 in patients with rheumatoid arthritis

AIM

Abnormal B-cell apoptosis is believed to have a role in rheumatoid arthritis (RA) pathogenesis, but the exact mechanisms of B-cell apoptosis in RA have not been elucidated. We therefore investigated the percentage of circulating B cells and its relationship with apoptosis in a cohort of patients with RA.

METHODS

B cells were quantified by flow cytometry in RA patients and matched controls, and the relationships between these proportions and RA disease parameters were calculated. Rates of apoptosis were determined by annexin V/propidium iodine analysis, and Bcl-2 and caspase-3 protein levels were determined by western blot.

RESULTS

RA patients had significantly higher percentage of B cells in the peripheral blood than healthy controls but a significantly lower rate of B-cell apoptosis. The percentage of B cells correlated with Disease Activity Score of 28 joints and serum immunoglobulin G concentration in RA patients. Expression of anti-apoptosis protein Bcl-2 was higher in RA patients than in healthy controls, whereas expression of apoptosis marker caspase-3 in B cells was lower.

CONCLUSION

The higher percentage of B cells in the peripheral blood of RA patients may be due, at least partially, to disruption of the normal pathway of apoptosis in these cells. The inhibition of B-cell apoptosis in these patients may be attributable to the enhanced expression of Bcl-2 in these cells.

The impact of biological therapy on regulatory T cells in rheumatoid arthritis

Regulatory T cells (Treg) are functionally defective in patients with RA. Restoring their function may not only control inflammation but also restore tolerance in these patients. Biologic therapies have been tremendously successful in treating RA. Here we review numerous reports suggesting that these immunomodulatory therapies have an impact on Treg and that this may contribute to their beneficial effects. Better understanding of their mode of action may not only lead to improvements in therapies and sustained remission but also enable the development of biomarkers of response, which would be the first steps towards personalized medicine.

B cells in rheumatoid arthritis: from pathogenic players to disease biomarkers

The therapeutic benefit of depleting B cells in rheumatoid arthritis (RA) has refocused attention on B cells with increasing awareness on their role in autoimmunity and their function beyond autoantibody production. The rapid increase in our comprehension of B-cell pathobiology is progressively opening novel perspectives in the area of B cell-targeted therapies with the expectation to define more specific approaches able to preserve the homeostasis of the humoral response while disrupting the pathogenic components. In parallel, B-cell activity in RA is starting to be explored in its clinical value, in search of novel biomarkers embedded in the pathogenic process that could help classifying the disease and predicting its heterogeneous outcome beyond inflammation dynamics. In this review, we summarize current knowledge on the multiple roles that B cells play in several aspects of RA. We also analyze their distribution and potential function in different anatomic compartments with specific reference to the main sites in which the disease may be sustained and exert its detrimental effects: the systemic circulation, synovium, bone marrow, and draining lymph nodes. We also highlight novel data encouraging further research in the field of biomarkers related to B cells and their regulatory factors.