Impairment of Granzyme B-Producing Regulatory B Cells Correlates with Exacerbated Rheumatoid Arthritis

MDSCs are important osteoclast precursors primed by B cells in rheumatoid arthritis

Osteoclast-mediated bone erosion and deformation represent significant pathological features in rheumatoid arthritis (RA). Myeloid-derived suppressor cells (MDSCs) and B cells have emerged as key contributors to the progression of RA. Nevertheless, their involvement, especially the interaction in RA osteoclastogenesis remains elusive. In this study, our results revealed a marked expansion of MDSCs in RA patients, and importantly, their abundance was positively correlated with radiographic damage evaluated by the Sharp/van der Heijde score. Notably, MDSCs derived from both RA patients and arthritic mice exhibited a heightened propensity to differentiate into osteoclasts compared with those from healthy individuals. Intriguingly, we observed that B cells from RA patients could augment the osteoclastogenic potential of MDSCs, which was also observed in arthritic mice. The impact of B cells on MDSC-mediated osteoclastogenesis was found to be most pronounced in switched memory B cells, followed by CD21low B cells and naïve B cells. MDSCs from B-cell-deficient mice exhibited diminished capacity to differentiate into osteoclasts, accompanied by distinct gene expression profiles associated with osteoclastogenesis. Taken together, our findings suggested that MDSCs were important osteoclast precursors primed by B cells in RA, serving as novel therapeutic targets for the persistent disease.

Granzyme serine proteases in inflammation and rheumatic diseases

Granzymes (granule-secreted enzymes) are a family of serine proteases that have been viewed as redundant cytotoxic enzymes since their discovery more than 30 years ago. Predominantly produced by cytotoxic lymphocytes and natural killer cells, granzymes are delivered into the cytoplasm of target cells through immunological synapses in cooperation with the pore-forming protein perforin. After internalization, granzymes can initiate cell death through the cleavage of intracellular substrates. However, evidence now also demonstrates the existence of non-cytotoxic, pro-inflammatory, intracellular and extracellular functions that are granzyme specific. Under pathological conditions, granzymes can be produced and secreted extracellularly by immune cells as well as by non-immune cells. Depending on the granzyme, accumulation in the extracellular milieu might contribute to inflammation, tissue injury, impaired wound healing, barrier dysfunction, osteoclastogenesis and/or autoantigen generation.

Breg-Mediated Immunoregulation in the Skin

Wound healing is a complex process involving a coordinated series of events aimed at restoring tissue integrity and function. Regulatory B cells (Bregs) are a subset of B lymphocytes that play an essential role in fine-tuning immune responses and maintaining immune homeostasis. Recent studies have suggested that Bregs are important players in cutaneous immunity. This review summarizes the current understanding of the role of Bregs in skin immunity in health and pathology, such as diabetes, psoriasis, systemic sclerosis, cutaneous lupus erythematosus, cutaneous hypersensitivity, pemphigus, and dermatomyositis. We discuss the mechanisms by which Bregs maintain tissue homeostasis in the wound microenvironment through the promotion of angiogenesis, suppression of effector cells, and induction of regulatory immune cells. We also mention the potential clinical applications of Bregs in promoting wound healing, such as the use of adoptive Breg transfer.

Differentially activated B cells develop regulatory phenotype and show varying immunosuppressive features: a comparative study

Regulatory B lymphocytes (Bregs) are B cells with well-pronounced immunosuppressive properties, allowing them to suppress the activity of effector cells. A broad repertoire of immunosuppressive mechanisms makes Bregs an attractive tool for adoptive cell therapy for diseases associated with excessive activation of immune reactions. Such therapy implies Breg extraction from the patient's peripheral blood, ex vivo activation and expansion, and further infusion into the patient. At the same time, the utility of Bregs for therapeutic approaches is limited by their small numbers and extremely low survival rate, which is typical for all primary B cell cultures. Therefore, extracting CD19+ cells from the patient's peripheral blood and specifically activating them ex vivo to make B cells acquire a suppressive phenotype seems to be far more productive. It will allow a much larger number of B cells to be obtained initially, which may significantly increase the likelihood of successful immunosuppression after adoptive Breg transfer. This comparative study focuses on finding ways to efficiently manipulate B cells in vitro to differentiate them into Bregs. We used CD40L, CpG, IL4, IL21, PMA, and ionomycin in various combinations to generate immunosuppressive phenotype in B cells and performed functional assays to test their regulatory capacity. This work shows that treatment of primary B cells using CD40L + CpG + IL21 mix was most effective in terms of induction of functionally active regulatory B lymphocytes with high immunosuppressive capacity ex vivo.

Impaired regulatory function of granzyme B-producing B cells against T cell inflammatory responses in lupus mice

OBJECTIVE

Recently, a new subtype of granzyme B (GrB)-producing Breg cells has been identified, which was proven to be involved in autoimmune disease. Our recent report demonstrated that GrB-producing Breg cells were correlated with clinical and immunological features of SLE. However, the effect of GrB-producing Breg cells in lupus mice is unclear.

METHODS

GrB expression in naïve and lupus mouse B cells was analysed using flow cytometry, PCR, ELISA and ELISpot assays. To study the role of GrB-producing B cells in a lupus model, GrB knockout (KO) and wild-type (WT) mice were intraperitoneally injected with monoclonal cells from the mutant mouse strain B6.C-H-2bm12 (bm12) for 2 weeks. In addition, the function of GrB-producing Breg cells in naïve and lupus mice was further explored using in vitro B cells-CD4⁺CD25^- T cell co-culture assays with GrB blockade/KO of B cells.

RESULTS

B cells from the spleens of WT C57BL/6 (B6) mice could express and secret GrB (p<0.001). GrB-producing Breg cells from WT mice showed their regulatory functions on CD4⁺CD25^- T cell. While the frequency of GrB-producing Breg cells was significantly decreased (p=0.001) in lupus mice (p<0.001). Moreover, GrB-producing Breg cells in lupus mice failed to suppress T cell-mediated proinflammatory responses, partially due to the impaired capacity of downregulating the T cell receptor-zeta chain and inducing CD4⁺CD25^- T cell apoptosis.

CONCLUSION

This study further revealed the function and mechanism of GrB-producing Breg cells in regulating T cell homeostasis in lupus mice and highlighted GrB-producing Breg cells as a therapeutic target in SLE.

Immunomodulatory Effects of Microbiota-Derived Short-Chain Fatty Acids in Autoimmune Liver Diseases

Nonpathogenic commensal microbiota and their metabolites and components are essential to maintain a tolerogenic environment and promote beneficial health effects. The metabolic environment critically impacts the outcome of immune responses and likely impacts autoimmune and allergic responses. Short-chain fatty acids (SCFAs) are the main metabolites produced by microbial fermentation in the gut. Given the high concentration of SCFAs in the gut and portal vein and their broad immune regulatory functions, SCFAs significantly influence immune tolerance and gut-liver immunity. Alterations of SCFA-producing bacteria and SCFAs have been identified in a multitude of inflammatory diseases. These data have particular significance in primary biliary cholangitis, primary sclerosing cholangitis, and autoimmune hepatitis because of the close proximity of the liver to the gut. In this focused review, we provide an update on the immunologic consequences of SCFA-producing microbiota and in particular on three dominant SCFAs in autoimmune liver diseases.

Novel Potential Mechanisms of Regulatory B Cell-Mediated Immunosuppression

B lymphocytes play an important role in the regulation of immune response in both normal and pathological conditions. Traditionally, the main functions of B cells were considered to be antibody production and antigen presentation, but in recent decades there have been discovered several subpopulations of regulatory B lymphocytes (Bregs), which maintain immunological tolerance and prevent overactivation of the immune system. Memory (mBregs, CD19⁺CD24^hiCD27⁺) and transitional (tBregs, CD19⁺CD24^hiCD38^hi) subpopulations of Bregs are usually considered in the context of studying the role of these B cells in various human pathologies. However, the mechanisms by which these Breg subpopulations exert their immunosuppressive activity remain poorly understood. In this work, we used bioinformatic analysis of open-source RNA sequencing data to propose potential mechanisms of B cell-mediated immunosuppression. Analysis of differential gene expression before and after activation of these subpopulations allowed us to identify six candidate molecules that may determine the functionality of mBregs and tBregs. IL4I1-, SIRPA-, and SLAMF7-dependent mechanisms of immunosuppression may be characteristic of both Breg subsets, while NID1-, CST7-, and ADORA2B-dependent mechanisms may be predominantly characteristic of tBregs. In-depth understanding of the molecular mechanisms of anti-inflammatory immune response of B lymphocytes is an important task for both basic science and applied medicine and could facilitate the development of new approaches to the therapy of complex diseases.

Role of the granzyme family in rheumatoid arthritis: Current Insights and future perspectives

Rheumatoid arthritis (RA) is a complex autoimmune disease characterized by chronic inflammation that affects synovial tissues of multiple joints. Granzymes (Gzms) are serine proteases that are released into the immune synapse between cytotoxic lymphocytes and target cells. They enter target cells with the help of perforin to induce programmed cell death in inflammatory and tumor cells. Gzms may have a connection with RA. First, increased levels of Gzms have been found in the serum (GzmB), plasma (GzmA, GzmB), synovial fluid (GzmB, GzmM), and synovial tissue (GzmK) of patients with RA. Moreover, Gzms may contribute to inflammation by degrading the extracellular matrix and promoting cytokine release. They are thought to be involved in RA pathogenesis and have the potential to be used as biomarkers for RA diagnosis, although their exact role is yet to be fully elucidated. The purpose of this review was to summarize the current knowledge regarding the possible role of the granzyme family in RA, with the aim of providing a reference for future research on the mechanisms of RA and the development of new therapies.

Granzyme B in circulating CD8+ T cells as a biomarker of immunotherapy effectiveness and disability in neuromyelitis optica spectrum disorders

BACKGROUND AND OBJECTIVE

Neuromyelitis optica spectrum disorders (NMOSD) are chronical inflammatory demyelinating diseases of the central nervous system (CNS) and the underlying mechanism remains unclear. Several recent studies have demonstrated that T cells play a pivotal role in the pathogenesis of NMOSD.In this study, we investigated CD8+ T cell phenotypes and levels of the cytotoxic protein granzyme B (GzmB), as well as their potential clinical application in NMOSD.

METHODS

In this study, 90 peripheral blood samples were collected from 59 NMOSD patients with seropositive anti-aquaporin-4 (AQP4) antibodies and 31 sex- and age-matched healthy donors (HDs). Flow cytometry was used to detect circulating levels of GzmB and CD8+ T cell subpopulations, including naïve (TN, CCD7+CD45RA+), central memory (TCM, CCD7+CD45RA-), effector memory (TEM, CCD7-CD45RA-), terminal differentiation effector memory cells (TEMRA, CCD7-CD45RA+) in both groups. The associations between GzmB levels in CD8+T cells and clinical characteristics of NMOSD were evaluated.

RESULTS

NMOSD patients exhibited significantly decreased proportions of CD8+TN cells and increased proportions of highly differentiated CD8+T cells (TEMRA) compared with HDs. In addition, levels of GzmB in CD8+ T cells were markedly higher in NMOSD patients than in HDs. Moreover, we observed that high proportions of GzmB-expressing CD8+ T cells were more common in patients with a poor response to immunotherapies, and showed a good potential to distinguish poor responders from responders (ACU=0.89). Clinical correlation analysis indicated that high levels of GzmB in CD8+ T cells were not only related to severe disability but also significantly associated with increased serum levels of neurofilament light (NFL) and glial fibrillary acidic protein (GFAP). Multivariate linear regression analyses further suggested that GzmB expression in CD8+ T cells was predominantly associated with disability and immunotherapy effectiveness in NMOSD, independent of the sex, age, and disease phase. Transcription factor T-bet in CD8+ T cells were also significantly elevated in NMOSD and were associated with increasing number of circulating CD8+TEMRA cells and GzmB-expressing CD8+T cells.

CONCLUSIONS

Our study support the involvement of GzmB-expressing CD8+ T cells in the inflammatory response in patients with NMOSD and provide a potential biomarker for disease immunotherapy effectiveness and disability progression.

Suppressive mechanisms of regulatory B cells in mice and humans

B cells include immune-suppressive fractions, called regulatory B cells (Bregs), which regulate inflammation primarily through an interleukin 10 (IL-10)-mediated inhibitory mechanism. Several B-cell fractions have been reported as IL-10-producing Bregs in murine disease models and human inflammatory responses including autoimmune diseases, infectious diseases, cancer and organ-transplant rejection. Although the suppressive functions of Bregs have been explored through the hallmark molecule IL-10, inhibitory cytokines and membrane-binding molecules other than IL-10 have also been demonstrated to contribute to Breg activities. Transcription factors and surface antigens that are characteristically expressed in Bregs are also being elucidated. Nevertheless, defining Bregs is still challenging because their active periods and differentiation stages vary among disease models. The identity of the diverse Breg fractions is also under debate. In the first place, since regulatory functions of Bregs are mostly evaluated by ex vivo stimulation, the actual in vivo phenotypes and functions may not be reflected by the ex vivo observations. In this article, we provide a historical overview of studies that established the characteristics of Bregs and review the various suppressive mechanisms that have been reported to be used by Bregs in murine and human disease conditions. We are only part-way through but the common phenotypes and functions of Bregs are still emerging.

c-Myc-driven glycolysis polarizes functional regulatory B cells that trigger pathogenic inflammatory responses

B cells secreting IL-10 functionally are recognized as functional regulatory B (Breg) cells; however, direct evidence concerning the phenotype, regulation, and functional and clinical relevance of IL-10-secreting Breg cells in humans is still lacking. Here, we demonstrate that, although IL-10 itself is anti-inflammatory, IL-10+ functional Breg cells in patients with systemic lupus erythematosus (SLE) display aggressive inflammatory features; these features shift their functions away from inducing CD8+ T cell tolerance and cause them to induce a pathogenic CD4+ T cell response. Functional Breg cells polarized by environmental factors (e.g., CPG-DNA) or directly isolated from patients with SLE mainly exhibit a CD24intCD27-CD38-CD69+/hi phenotype that is different from that of their precursors. Mechanistically, MAPK/ERK/P38-elicited sequential oncogenic c-Myc upregulation and enhanced glycolysis are necessary for the generation and functional maintenance of functional Breg cells. Consistently, strategies that abrogate the activity of ERK, P38, c-Myc, and/or cell glycolysis can efficiently eliminate the pathogenic effects triggered by functional Breg cells.

The Rising Era of “Immunoporosis”: Role of Immune System in the Pathophysiology of Osteoporosis

Discoveries in the last few years have emphasized the existence of an enormous breadth of communication between bone and the immune system in maintaining skeletal homeostasis. Originally, the discovery of various factors was assigned to the immune system viz. interleukin (IL)-6, IL-10, IL-17, tumor necrosis factor (TNF)-α, receptor activator of nuclear factor kappa B ligand (RANKL), nuclear factor of activated T cells (NFATc1), etc., but now these factors have also been shown to have a significant impact on osteoblasts (OBs) and osteoclasts (OCs) biology. These discoveries led to an alteration in the approach for the treatment of several bone pathologies including osteoporosis. Osteoporosis is an inflammatory bone anomaly affecting more than 500 million people globally. In 2018, to highlight the importance of the immune system in the pathophysiology of osteoporosis, our group coined the term “immunoporosis”. In the present review, we exhaustively revisit the characteristics, mechanism of action, and function of both innate and adaptive immune cells with the goal of understanding the potential of immune cells in osteoporosis. We also highlight the Immunoporotic role of gut microbiota (GM) for the treatment and management of osteoporosis. Importantly, we further discuss whether an immune cell-based strategy to treat and manage osteoporosis is feasible and relevant in clinical settings.

Impaired granzyme B-producing regulatory B cells in systemic lupus erythematosus

Granzyme B (GrB)-producing B cells are proposed to be a kind of regulatory B cells (Bregs) and have been revealed to be implicated in the pathogenesis of autoimmune diseases. Nevertheless, their role in SLE remains elusive. In this study, the frequencies of GrB-producing Bregs in peripheral blood of heathy control (HC) and systemic lupus erythematosus (SLE) were evaluated by flow cytometry, and their correlation with SLE patient clinical and immunological features were analyzed. The expression of GrB in HC and SLE B cells were also further detected by RT-qPCR analysis and ELISpot. The function of GrB-producing Bregs in HC and SLE patients was further investigated by in vitro CD4⁺ effector T cells-B cells co-culture assays with GrB blockade. We found that GrB-producing Bregs were significantly decreased in SLE patients and correlated with the clinical and immunological features. Moreover, these cells were functionally impaired under SLE circumstance. The negative correlation between GrB-producing Bregs and CD4⁺ T cells observed in healthy individuals disappeared in SLE patients. In vitro cell co-culture assay further showed that GrB-producing Bregs from SLE patients failed to suppress the Th1, Th2 and Th17 cell inflammatory responses, partially due to the dampened capacity of down-regulating TCR zeta and inducing T cell apoptosis. Taken together, these results revealed the disturbance of GrB-producing Bregs in SLE that might contribute to the disease initiation and progression.

Altered peripheral B lymphocyte homeostasis and functions mediated by IL-27 via activating the mammalian target of rapamycin signaling pathway in patients with rheumatoid arthritis

B cell dysfunction and inflammatory cytokine over-production participate in the pathogenesis of rheumatoid arthritis (RA). Here we compared peripheral B cell homeostasis and immune functions between RA patients and healthy controls (HC) and explored vital signaling pathways involved in altered RA B cells. We found that RA patients showed significantly decreased frequencies of peripheral CD19⁺ CD27⁺ CD24^high regulatory B (Breg) cells but increased frequencies of CD19⁺ CD27⁺ CD38^high plasmablasts and CD19⁺ CD138⁺ plasma cells, and higher levels of serum immunoglobulin (Ig)M and IgG. Compared to HC peripheral B cells, RA peripheral B cells had more increased proliferation and higher expression of activation markers. Importantly, our results showed that RA peripheral B cells displayed the mTOR signaling pathway to be more activated, and inhibition of mTOR could restore RA B cell homeostasis and functions. RA serum-treated B cells exhibited more increased expressions of mTOR, which could be restored with the addition of anti-interleukin (IL)-27 neutralizing antibody. Serum IL-27 levels were significantly increased in RA patients and positively correlated with disease activity, the frequencies of plasma cells and the levels of autoantibodies. In vitro, IL-27 notably promoted immune dysfunction of RA B cells, which were inhibited by anti-IL-27 neutralizing antibody. Also, the mTOR pathway was more activated in IL-27-treated RA B cells, and mTOR inhibition apparently reversed abnormalities of RA B cells mediated by IL-27. These results suggest that increased serum IL-27 levels could promote peripheral B cell dysfunction in RA patients via activating the mTOR signaling pathway. Thus, IL-27 may play a pro-pathogenic role in the development of RA, and antagonizing IL-27 could be a novel therapy strategy for RA.

The Multiple Roles of B Cells in the Pathogenesis of Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease characterized by lymphocytic infiltration and tissue destruction of exocrine glands such as salivary glands. Although the formation of ectopic lymphoid tissue in exocrine glands and overproduction of autoantibodies by autoreactive B cells highlight the critical involvement of B cells in disease development, the precise roles of various B cell subsets in pSS pathogenesis remain partially understood. Current studies have identified several novel B cell subsets with multiple functions in pSS, among which autoreactive age-associated B cells, and plasma cells with augmented autoantibody production contribute to the disease progression. In addition, tissue-resident Fc Receptor-Like 4 (FcRL4)⁺ B cell subset with enhanced pro-inflammatory cytokine production serves as a key driver in pSS patients with mucosa-associated lymphoid tissue (MALT)-lymphomas. Recently, regulatory B (Breg) cells with impaired immunosuppressive functions are found negatively correlated with T follicular helper (Tfh) cells in pSS patients. Further studies have revealed a pivotal role of Breg cells in constraining Tfh response in autoimmune pathogenesis. This review provides an overview of recent advances in the identification of pathogenic B cell subsets and Breg cells, as well as new development of B-cell targeted therapies in pSS patients.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Interaction Networks Converging on Immunosuppressive Roles of Granzyme B: Special Niches Within the Tumor Microenvironment

Granzyme B is a renowned effector molecule primarily utilized by CTLs and NK cells against ill-defined and/or transformed cells during immunosurveillance. The overall expression of granzyme B within tumor microenvironment has been well-established as a prognostic marker indicative of priming immunity for a long time. Until recent years, increasing immunosuppressive effects of granzyme B are unveiled in the setting of different immunological context. The accumulative evidence confounded the roles of granzyme B in immune responses, thereby arousing great interests in characterizing detailed feature of granzyme B-positive niche. In this paper, the granzyme B-related regulatory effects of major suppressor cells as well as the tumor microenvironment that defines such functionalities were longitudinally summarized and discussed. Multiplex networks were built upon the interactions among different transcriptional factors, cytokines, and chemokines that regarded to the initiation and regulation of granzyme B-mediated immunosuppression. The conclusions and prospect may facilitate better interpretations of the clinical significance of granzyme B, guiding the rational development of therapeutic regimen and diagnostic probes for anti-tumor purposes.

New Method for the Expansion of Highly Purified Human Regulatory Granzyme B-Expressing B Cells

Granzyme B (GZMB)-expressing B cells inhibit CD4⁺ T-lymphocyte proliferation in a contact- and GZMB-dependent manner, through degradation of TCR zeta or induction of T-cell apoptosis. This regulatory B-cell population is present in human healthy individuals and represents about 1% of circulating B cells. Their small proportion requires the development of expansion methods to enable their study and envision clinical applications. We describe here how to expand GZMB-expressing B cells to obtain more than 90% of highly purified GZMB⁺ B cells, and the protocol of B/T cells coculture for the evaluation of the suppressive function of the GZMB⁺ B-cell population.

Elevated serum granzyme B levels are associated with disease activity and joint damage in patients with rheumatoid arthritis

OBJECTIVES

Little is known about the roles of granzyme B in rheumatoid arthritis (RA). We aimed to evaluate the serum level of granzyme B in patients with RA and determine relationships with clinical features and joint destruction of RA.

METHODS

We enrolled 100 patients with RA, 50 patients with osteoarthritis (OA), and 50 healthy controls (HC). Granzyme B serum concentrations were measured by ELISA; we then analyzed associations between granzyme B levels, clinical features, and joint destruction by calculating Sharp scores and disease activity as measured by Disease Activity Score-28 based on erythrocyte sedimentation rate (DAS28-ESR) in patients with RA.

RESULTS

Compared with HC and patients with OA, serum granzyme B levels in patients with RA were remarkably elevated. Serum granzyme B levels did not differ between patients with OA and HC. Granzyme B levels correlated with ESR, rheumatoid factor, swollen joint counts, joint erosion scores, total Sharp scores, and DAS28-ESR. Moreover, patients with RA with high disease activity had higher granzyme B levels.

CONCLUSIONS

Serum granzyme B levels were elevated significantly in patients with RA and correlated positively with disease activity and joint destruction. Serum granzyme B may have potential applications in laboratory evaluation of patients with RA.

Innate Lymphocytes in Inflammatory Arthritis

Inflammatory arthritis (IA) refers to a group of chronic diseases, including rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS), and other spondyloarthritis (SpA). IA is characterized by autoimmune-mediated joint inflammation and is associated with inflammatory cytokine networks. Innate lymphocytes, including innate-like lymphocytes (ILLs) expressing T or B cell receptors and innate lymphoid cells (ILCs), play important roles in the initiation of host immune responses against self-antigens and rapidly produce large amounts of cytokines upon stimulation. TNF (Tumor Necrosis Factor)-α, IFN (Interferon)-γ, Th2-related cytokines (IL-4, IL-9, IL-10, and IL-13), IL-17A, IL-22, and GM-CSF are involved in IA and are secreted by ILLs and ILCs. In this review, we focus on the current knowledge of ILL and ILC phenotypes, cytokine production and functions in IA. A better understanding of the roles of ILLs and ILCs in IA initiation and development will ultimately provide insights into developing effective strategies for the clinical treatment of IA patients.

Regulatory B Cells and Its Role in Central Nervous System Inflammatory Demyelinating Diseases

Regulatory B (Breg) cells represent a population of suppressor B cells that participate in immunomodulatory processes and inhibition of excessive inflammation. The regulatory function of Breg cells have been demonstrated in mice and human with inflammatory diseases, cancer, after transplantation, and particularly in autoinflammatory disorders. In order to suppress inflammation, Breg cells produce anti-inflammatory mediators, induce death ligand-mediated apoptosis, and regulate many kinds of immune cells such as suppressing the proliferation and differentiation of effector T cell and increasing the number of regulatory T cells. Central nervous system Inflammatory demyelinating diseases (CNS IDDs) are a heterogeneous group of disorders, which occur against the background of an acute or chronic inflammatory process. With the advent of monoclonal antibodies directed against B cells, breakthroughs have been made in the treatment of CNS IDDs. Therefore, the number and function of B cells in IDDs have attracted attention. Meanwhile, increasing number of studies have confirmed that Breg cells play a role in alleviating autoimmune diseases, and treatment with Breg cells has also been proposed as a new therapeutic direction. In this review, we focus on the understanding of the development and function of Breg cells and on the diversification of Breg cells in CNS IDDs.

Autoimmune diseases in China

Autoimmune diseases, such as rheumatoid arthritis, systematic lupus erythematosus and Sjögren's syndrome, are a group of diseases characterized by the activation of immune cells and excessive production of autoantibodies. Although the pathogenesis of these diseases is still not completely understood, studies have shown that multiple factors including genetics, environment and immune responses play important roles in the development and progression of the diseases. In China, there are great achievements in the mechanisms of autoimmune diseases during the last decades. These studies provide new insight to understand the diseases and also shed light on the development of novel therapy.

The proportion of CD19+CD24hiCD27+ regulatory B cells predicts the occurrence of acute allograft rejection in liver transplantation

Background

Regulatory B cells (Bregs) play an essential role in inflammation and transplant tolerance. Several studies have reported a decreased number of Bregs in renal transplant patients with graft rejection. However, little is known about their role in the liver alloresponse.

Methods

To investigate whether the circulating Bregs have been associated with acute allograft rejection (AR) in liver transplantation patients, 19 patients receiving liver allografts from donation after cardiac death (DCD) donors were retrospectively studied.

Results

The postoperative proportions of circulating CD19⁺CD24^hiCD38^hi transitional Bregs (tBregs) and CD19⁺CD24^hiCD27⁺ memory Bregs (mBregs) in patients diagnosed with AR (AR group) and other patients with stable allograft liver function (SF group) were evaluated using flow cytometry (FCM) analysis. Results showed that while no significant changes were found regarding both the tBreg and mBreg, proportions across all time points in the SF group, the AR group showed significantly decreased proportions of mBregs. All of the five AR patients responded fine to the treatments, and the proportions of mBregs increased significantly after anti-rejection therapies. In addition, AR was suspected in four recipients, but gradually they were diagnosed with hemolytic or obstructive jaundice and showed no decrease in the proportion of mBregs.

Conclusions

For the first time, our results suggested the potential role of a decreased proportion of circulating mBregs in predicting AR in patients with post liver transplantation.

Human Pathway-Based Disease Network

Constructing disease-disease similarity network is important in elucidating the associations between the origin and molecular mechanism of diseases, and in researching disease function and medical research. In this paper, we use a high-quality protein interaction network and a collection of pathway databases to construct a Human Pathway-based Disease Network (HPDN) to explore the relationship between diseases and their intrinsic interactions. We find that the similarity of two diseases has a strong correlation with the number of their shared functional pathways and the interaction between their related gene sets. Comparing HPDN with disease networks based on genes and symptoms respectively, we find the three networks have high overlap rates. Additionally, HPDN can predict new disease-disease correlations, which are supported by Comparative Toxicogenomics Database (CTD) benchmark and large-scale biomedical literature database. The comprehensive, high-quality relations between diseases based on pathways can further be applied to study important matters in systems medicine, for instance, drug repurposing. Based on a dense subgraph in our network, we find two drugs, prednisone and folic acid, may have new indications, which will provide potential directions for the treatments of complex diseases.

[Role of erythroblast-like Ter cells in the pathogenesis of collagen-induced arthritis]

OBJECTIVE

To explore the role of Ter cells in the development of the collagen-induced arthritis (CIA), we detected their quantity changes in the spleen of different stages of CIA mice and analyzed the correlation between Ter cells and the joint scores, and we also analyzed the correlation between Ter cells and the frequencies of T and B cell subsets, so as to further understand the pathogenesis of rheumatoid arthritis.

METHODS

The six to eight weeks DBA/1 mice were used to prepare CIA model. After the second immunization, we began to evaluate the joint score. According to the time of CIA onset and the joint score, the CIA mice were divided into three stages: early, peak and late stages. According to the final joint score, the CIA mice at the peak stage were subdivided into the high score group (score>8) and the low score group (score≤8). The frequencies of Ter cells in the spleen of the naïve mice and the CIA mice at various stages and the frequencies of T and B cell subsets in the spleen of the CIA mice at the peak stage were detected by flow cytometry, then we carried on the correlation analysis.

RESULTS

The frequencies of Ter cells in the spleen of the CIA mice was significantly higher than those of the naïve mice (8.522%±2.645% vs. 1.937%±0.725%, P<0.01), the frequencies of Ter cells in the spleen of the high score group mice was significantly lower than those of the low score group (6.217%±0.841% vs. 10.827%±0.917%, P<0.01). The frequencies of Th1 cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.337%±0.110% vs. 0.727%±0.223%, P<0.05). The frequencies of Th17 cells in the spleen of the high score group mice was higher than those of the low score group mice (0.750%±0.171% vs. 0.477%±0.051%, P=0.099). The frequencies of germinal center B cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.243%±0.057% vs. 1.097%±0.015%, P<0.05). Correlation analysis results showed that the frequencies of Ter cells in the spleen of the CIA mice at the peak stage was strongly negatively correlated with the frequencies of CD4+ T, Th1, Th17, and germinal center B cells, and was strongly positively correlated with the frequencies of B10 cells, indicating that these cells might have a protective effect in CIA. Studies on dynamic changes showed that the frequencies of Ter cells in the spleen of the CIA mice at the late stage was significantly lower than those at the peak stage (0.917%±0.588% vs. 8.522%±2.645%, P<0.001), suggesting the protective effect of these cells in arthritis.

CONCLUSION

Ter cells were significantly increased in the spleen of the CIA mice at peak stage, and were negatively correlated with joint scores and pathogenic immune cells, and positively correlated with protective immune cells. Ter cells were significantly decreased in the spleen of the CIA mice at the late stage. What we mentioned above suggests that Ter cells might be involved in the progression of rheumatoid arthritis as an immunomodulatory cell,but further in vivo and in vitro experiments are needed to verify its specific effects and mechanism.

Sexual dimorphism in Th17/Treg axis in lymph nodes draining inflamed joints in rats with collagen-induced arthritis

Collagen type II-induced arthritis (CIA) in Dark Agouti rats, a model of rheumatoid arthritis (RA), reproduces sexual dimorphism in the incidence and severity of the human disease. Th17 cells are central in the induction/propagation of autoimmune inflammation in CIA and RA. To assess mechanisms underlying this dimorphism in CIA rats, in lymph nodes draining inflamed joints and adjacent tissues (dLNs) from CIA rats of both sexes Th17/CD25+Foxp3+CD4+ T-regulatory cell (Treg) ratio, Th17 cell redifferentiation in functionally distinct subsets and Treg transdifferentiation into IL-17-producing cells (exTregs) were examined. In female rats (developing more severe CIA than their male counterparts) the higher frequency of all Th17 cells (reflecting partly their greater proliferation), followed by the higher frequency of highly pathogenic IFN-γ/GM-CSF-co-producing cells, but lower frequency of less pathogenic/immunoregulatory IL-10-producing cells among them was found. Additionally, compared with male rats, in female rats the lower frequency of Tregs was observed. Moreover, Tregs from female rats exhibited diminished proliferative and suppressive capacity (judging by PD-1 expression) and enhanced conversion into IL-17-producing cells. Given that TGF-β concentration was comparable in collagen-type II-stimulated dLN cell cultures from female and male rats, the shift in Th17/Treg ratio followed by augmented Th17 cell redifferentiation into IFN-γ/GM-CSF-co-producing cells and Treg transdifferentiation into IL-17-producing cells in female rats was associated with increased concentration of IL-6 in female rat dLN cell cultures, and the higher frequency of IL-1β- and IL-23-producing cells among their dLN cells. The lower frequency of IL-10-producing B cells, presumably B regulatory cells (Bregs) could also contribute to the shift in Th17/Treg ratio in female rat compared with male rat dLNs. Consistently, the lower expression of IL-35 (the cytokine promoting Treg expansion directly and indirectly, by favoring Breg expansion and conversion into IL-10/IL-35-producing cells) in female rat dLN cells was detected. Thus, the study identified putative cellular and molecular substrates of the sexual dimorphism in the immunopathogenesis and clinical outcome of CIA and suggested mechanisms to be targeted in females to improve control of Th17 response, and consequently clinical outcome of CIA, and possibly RA.

Regulatory B cells and advances in transplantation

The effects of B cell subsets with regulatory activity on the immune response to an allograft have evoked increasing interest. Here, we summarize the function and signaling of regulatory B cells (Bregs) and their potential effects on transplantation. These cells are able to suppress the immune system directly via ligand-receptor interactions and indirectly by secretion of immunosuppressive cytokines, particularly IL-10. In experimental animal models, the extensively studied IL-10-producing B cells have shown unique therapeutic advantages in the transplant field. In addition, adoptive transfer of B cell subsets with regulatory activity may reveal a new approach to prolonging allograft survival. Recent clinical observations on currently available therapies targeting B cells have revealed that Bregs play an important role in immune tolerance and that these cells are expected to become a new target of immunotherapy for transplant-related diseases.

Regulatory B cell phenotype and mechanism of action: the impact of stimulating conditions

A diverse population of regulatory B (Breg) cells reportedly exhibits significant immunomodulatory effects in various models of inflammatory responses and infectious diseases caused by bacteria, viruses or parasites. Breg cells contribute to maintenance of homeostasis via IL-10 production and multiple IL-10-independent mechanisms. The current review describes various phenotypic and functional subsets of Breg cells in autoimmune and infectious diseases and discusses the impacts of experimental conditions that have been found to drive Breg cell differentiation.

Regulatory B cells: New players in inflammatory and autoimmune rheumatic diseases

OBJECTIVE

Regulatory B cells (Bregs) are a new subset of B cells with immunoregulatory functions, mainly through IL-10 production. Bregs suppress inflammatory Th1 and Th17 differentiation and induce Tregs suppressing autoimmune diseases. The aim of the study was to review the literature related to Bregs in autoimmune rheumatic diseases (ARDs).

METHODS

A literature review of publications in PUBMED published in English was performed using the relevant combinations of terms.

RESULTS

All relevant publications are discussed. Overall, recent studies in rheumatic diseases found Bregs to be decreased in ANCA-associated vasculitides (AAV) and in systemic sclerosis (SSc), particularly in SSc-associated lung fibrosis. In AAV Bregs levels are negatively correlated with autoantibody levels whereas in SSc this association is less clear but there is an inverse association with Th1 and Th17 cells. In rheumatoid arthritis (RA), Bregs were decreased, particularly in RA-associated lung fibrosis. In psoriatic arthritis IL-10 + Bregs are decreased and inversely associated with Th1 and Th17 cells. In systemic lupus erythematosus (SLE), the role of Bregs is unclear. In experimental diseases, when Bregs were expanded ex-vivo, they ameliorated established disease.

CONCLUSION

Bregs appear to be a new player in the pathogenesis of ARDs, and may offer a new strategy for therapeutic intervention.

Impaired CD27+IgD+ B Cells With Altered Gene Signature in Rheumatoid Arthritis

Natural antibodies, particularly natural IgM, are proved to play indispensable roles in the immune defenses against common infections. More recently, the protective roles of these natural IgM were also recognized in autoimmune diseases. They are mainly produced by B-1 and innate-like B cells (ILBs). Human CD19⁺CD27⁺IgD⁺ B cells, also termed as un-switched memory B cells, were proposed to be a kind of ILBs. However, functional features and characteristics of these cells in rheumatoid arthritis (RA) remained poorly understood. In this study, we found that human CD27⁺IgD⁺ B cells could produce natural antibody-like IgM. Under RA circumstance, the frequencies of these cells were significantly decreased. Moreover, the IgM-producing capacities of these cells were also dampened. Interestingly, the BCR repertoire of these cells was altered in RA, demonstrating decreased diversity with preferential usage alteration from VH3-23D to VH1-8. Single cell sequencing further revealed the proinflammatory biased features of these cells in RA. These CD27⁺IgD⁺ B cells were negatively correlated with RA patient disease activities and clinical manifestations. After effective therapy with disease remission in RA, these cells could be recovered. Taken together, these results have revealed that CD27⁺IgD⁺ B cells were impaired in RA with dysfunctional features, which might contribute to the disease perpetuation.

The molecular basis of immune regulation in autoimmunity

Autoimmune diseases can be triggered and modulated by various molecular and cellular characteristics. The mechanisms of autoimmunity and the pathogenesis of autoimmune diseases have been investigated for several decades. It is well accepted that autoimmunity is caused by dysregulated/dysfunctional immune susceptible genes and environmental factors. There are multiple physiological mechanisms that regulate and control self-reactivity, but which can also lead to tolerance breakdown when in defect. The majority of autoreactive T or B cells are eliminated during the development of central tolerance by negative selection. Regulatory cells such as Tregs (regulatory T) and MSCs (mesenchymal stem cells), and molecules such as CTLA-4 (cytotoxic T-lymphocyte associated antigen 4) and IL (interleukin) 10 (IL-10), help to eliminate autoreactive cells that escaped to the periphery in order to prevent development of autoimmunity. Knowledge of the molecular basis of immune regulation is needed to further our understanding of the underlying mechanisms of loss of tolerance in autoimmune diseases and pave the way for the development of more effective, specific, and safer therapeutic interventions.

IL-21 dependent Granzyme B production of B-cells is decreased in patients with lupus nephritis

OBJECTIVES

B-cells play a crucial role in the pathogenesis of lupus nephritis. Recently, a separate subset has been discovered characterized by expression of Granzyme B. The aim of this study is to investigate this subset in patients with systemic lupus erythematosus (SLE).

METHODS

Isolated PBMCs of SLE-patients (n=30) and healthy controls (n=21) were in vitro stimulated with CPG, IgG+IgM and IL-21. Patients were sub-grouped in patients with and without biopsy proven lupus nephritis. B-cells were analyzed for intracellular Granzyme B expression by flow cytometry.

RESULTS

The strongest stimulus for Granzyme B secretion of B-cells was IgG+IgM in presence of IL-21. SLE-patients had a significant decreased percentage of Granzyme B⁺ B-cells in particular SLE-patients with active disease and with lupus nephritis.

CONCLUSIONS

The frequency of GrB+ producing B-cells is reduced in SLE patients. This may contribute to an imbalanced B-cell regulation towards effector B-cells which might promote the development of lupus nephritis.