Not always the bad guys: B cells as regulators of autoimmune pathology

Co-expression of regulatory B-cell markers, transforming growth factor β and interleukin-10 as a prognostic factor in diffuse large B-cell lymphoma

Regulatory B cells (Bregs) suppress antitumor immunity by producing anti-inflammatory cytokines such as transforming growth factor β (TGF-β) and interleukin-10 (IL-10) and promoting tumor growth. It is unknown whether diffuse large B-cell lymphoma (DLBCL), a common subtype of B-cell malignancy, exhibits characteristics similar to those of Bregs. This study aimed to clarify the features of DLBCLs carrying Breg markers. In 123 DLBCL cases, we evaluated TGF-β and IL-10 expression in tumor biopsy samples using immunohistochemical staining and retrospectively analyzed their clinicopathological characteristics. Fifteen cases (12.2 %) classified as Breg-type DLBCL were positive for both TGF-β and IL-10. Breg-type DLBCL is mainly classified as having activated B cell-like cells of origin. Breg-type DLBCL cases showed significantly worse progression-free survival and overall survival (OS) than other DLBCL cases (P = 0.0016 and P = 0.042, respectively). In multivariate analysis, Breg-type DLBCL significantly affected OS (hazard ratio, 3.13; 95 % confidence interval 1.15-8.55; P = 0.025). Gene expression analysis showed that the expression of follicular dendritic cell-associated genes (FCER2, PIK3CD, FOXO1) was downregulated in Breg-type DLBCLs compared to other DLBCLs. These results suggest that the double expression of Breg markers, TGF-β and IL-10, in tumor cells indicates a poor prognosis in DLBCL patients. Further studies evaluating genomic abnormalities could confirm the characteristics of Breg-type DLBCL.

IL-10 dependent modulatory effect of regulatory B10 cells on local scar formation following Roux-en-Y choledochojejunostomy in a novel rat model

Choledochojejunostomy has been common surgical treatment of biliary tract disease. Scar formation at anastomotic often results in postoperative complications associated with bleak post-operative recovery, in which local inflammation may be a potential target to modulate local scar formation. This study investigated the effect of regulatory B10 cells on local scar formation through interleukin-10 signal pathway following Roux-en-Y choledochojejunostomy (RCJS) in a novel rat model. Sprague-Dawley (SD) rats with RCJS were randomly divided into blank group, experimental group, IL-10 blocking group, control group, and received different interventions and duration. Injected through dorsal vein of penis, rats in different groups were treated respectively according to scheme. These interventions were performed during surgery, on 1st day, and 2nd day after surgery. Related indexes, including blood examination, specimen tissue of anastomotic detection, were recorded and compared in different interventional groups. Rats in experimental groups had more rapid recovery in liver function and inflammatory index, and higher in IL-10 level. Flow cytometry analysis showed that rats in experimental groups had highest content of B10 cells and lowest content of CD4+CD25- T cells in peripheral blood. Wider anastomotic by macroscopical observation, and slighter proliferation of collagen fiber and smooth muscle fiber, lower α-SMA and TGF-β1 levels by pathological staining were detected in experimental groups. Higher expression of the IL-10 gene and lower expression of TGF-β1 at anastomotic were detected in experimental groups. B10 cells may relieve local inflammation of anastomotic following RCJS in rats through IL-10-dependent modulatory effect, and improve local scar formation.

Noticeable immune dysregulation-and-suppression in parvovirus affected dogs

Canine parvovirus type 2 (CPV-2) is one of the most common causes of infectious diarrhea in small animals, with high mortality and morbidity. Information on the specific treatment option(s) for CPV diseases (CPVD) is unachievably little. So, the treatment is mainly supportive one. Disruption of dog's innate immune system in viral diseases simply occurs; presumably, the CPV-2 may change the level of some TLRs, interleukins, CD4 and CD8 in the leukocytes of CPVD dogs, and disruptive activities of these immune molecules might be attributable to severe CPVD in dogs. Study on the role of the key immune molecules in CPVD is rare. Herein, by conducting and relating the clinical, para-clinical, immunological and molecular diagnostic tests, we tried to establish how some key immune molecules behave in blood of parvovirus affected dogs. As such, in the 1st study, the mRNA levels of TLR2, TLR4, TLR9, IL-1β, IL-6, CD4 and CD8 genes in the leukocytes of CPVD were assessed with quantitative (q)RT-PCR along with CPV-2 detection by rapid immunochromatography and PCR tests. In a 2nd study, the same measurements as in the 1st study were evaluated in two groups of mild versus severe clinical signs of CPVD. Both in the 1st and the 2nd studies leukopenia, much more pronounced in the severe CPVD, and immune dysregulation were observed. In the 1st study, a noticeable increase in the mRNA levels of TLR2 and TLR4 was detected with a slight decrease in TLR9 and a significant decrease in the expression of IL-1β, IL-6, CD4 and CD8 in leukocytes of CPV-infected dogs. Compared to the mild CPVD, the intense of downregulating effects on those immune molecules in the 2nd study was remarkably much more pronounced in the severe CPVD. Overall, it proves strong immune dysregulation and suppression/incompetence and potential T-cells exhaustion in severely CPV-2-affected dogs. Technically and clinically, this would be substantially applicable in canine medicine. By targeting those key immune molecules and their signaling pathways, new clinicodiagnostic approaches for CPVD can be evolved, and biotechnicoclinically this would be substantially applicable in all physiopathological conditions of dogs.

Crosstalk of Inflammatory Cytokines within the Breast Tumor Microenvironment

Several immune and immunocompetent cells, including dendritic cells, macrophages, adipocytes, natural killer cells, T cells, and B cells, are significantly correlated with the complex discipline of oncology. Cytotoxic innate and adaptive immune cells can block tumor proliferation, and others can prevent the immune system from rejecting malignant cells and provide a favorable environment for tumor progression. These cells communicate with the microenvironment through cytokines, a chemical messenger, in an endocrine, paracrine, or autocrine manner. These cytokines play an important role in health and disease, particularly in host immune responses to infection and inflammation. They include chemokines, interleukins (ILs), adipokines, interferons, colony-stimulating factors (CSFs), and tumor necrosis factor (TNF), which are produced by a wide range of cells, including immune cells, such as macrophages, B-cells, T-cells, and mast cells, as well as endothelial cells, fibroblasts, a variety of stromal cells, and some cancer cells. Cytokines play a crucial role in cancer and cancer-related inflammation, with direct and indirect effects on tumor antagonistic or tumor promoting functions. They have been extensively researched as immunostimulatory mediators to promote the generation, migration and recruitment of immune cells that contribute to an effective antitumor immune response or pro-tumor microenvironment. Thus, in many cancers such as breast cancer, cytokines including leptin, IL-1B, IL-6, IL-8, IL-23, IL-17, and IL-10 stimulate while others including IL-2, IL-12, and IFN-γ, inhibit cancer proliferation and/or invasion and enhance the body's anti-tumor defense. Indeed, the multifactorial functions of cytokines in tumorigenesis will advance our understanding of cytokine crosstalk pathways in the tumor microenvironment, such as JAK/STAT, PI3K, AKT, Rac, MAPK, NF-κB, JunB, cFos, and mTOR, which are involved in angiogenesis, cancer proliferation and metastasis. Accordingly, targeting and blocking tumor-promoting cytokines or activating and amplifying tumor-inhibiting cytokines are considered cancer-directed therapies. Here, we focus on the role of the inflammatory cytokine system in pro- and anti-tumor immune responses, discuss cytokine pathways involved in immune responses to cancer and some anti-cancer therapeutic applications.

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.

Unraveling the Immune Microenvironment of Thymic Epithelial Tumors: Implications for Autoimmunity and Treatment

Thymic Epithelial Tumors (TETs) represent a rare tumor family, originating from the epithelial component of the thymus gland. Clinicopathologically, they are segregated into six major subtypes, associated with distinct histological features and clinical outcomes. Their emergence and evolution are accompanied by the generation of a complex tumor microenvironment (TME), dominated by phenotypically and functionally divergent immune cellular subsets, in different maturation states and in analogies that vary significantly among different subtypes. These heterogenous leukocyte populations exert either immune-permissive and tumor-suppressive functions or vice versa, and the dynamic equilibrium established among them either dictates the tumor immune milieu towards an immune-tolerance state or enables the development of a productive spontaneous tumoricidal response. The immunologically “hot” microenvironment, defining a significant proportion of TETs, makes them a promising candidate for the implementation of immune checkpoint inhibitors (ICIs). A number of phase I and II clinical trials have already demonstrated significant, type-specific clinical efficacy of PD-L1 inhibitors, even though substantial limitations in their utilization derive from their immune-mediated adverse effects. Moreover, the completed clinical studies involved relatively restricted patient samples and an expansion in the enrolled cohorts is required, so that more trustworthy conclusions regarding the benefit from ICIs in TETs can be extracted.

Treatment of experimental autoimmune encephalomyelitis using AAV gene therapy by blocking T cell costimulatory pathways

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS), characterized by inflammation and demyelination. Presently, repeated relapses of MS necessitate long-term immune-regulatory therapy. Blocking the CD28-B7 and CD40-CD40L costimulatory pathways is an effective and synergistic method for the prevention and amelioration of clinical symptoms of experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. In this study, to explore the efficacy and safety of MS gene therapy, we used adeno-associated virus (AAV) as a vector to deliver CTLA4-immunoglobulin (Ig) or CD40-Ig on the EAE induced by myelin oligodendrocyte glycoprotein (MOG). Our results showed that a single administration of AAV8-CTLA4-Ig, either alone or with AAV8-CD40-Ig, protected mice from EAE and reversed disease progression. Decreased CD4⁺ and CD8⁺ T cell infiltration, inhibition of MOG antibody response, and downregulation of neuroinflammation were observed in mice receiving AAV, suggesting that autoimmunity was suppressed in EAE pathology. Moreover, no hematological or hepatic toxicity was observed in AAV-treated mice. Thus, compared with treatment with recombinant CTLA4-Ig (belatacept), AAV gene therapy could effectively control clinical symptoms and suppress autoimmunity in the long term. In summary, our study provides a potential therapeutic method for blocking T cell costimulation for the treatment of MS via gene therapy.

The Preliminary Evaluation of Epigenetic Modifications Regulating the Expression of IL10 in Insulin-Resistant Adipocytes

A higher level of IL10 expression in obesity and insulin resistance was observed in both human and mouse WAT. In our research, we analyzed the influence of insulin resistance on epigenetic modification within the promoter region IL10 gene and the potential influence of these modifications on its expression. Studies were performed using two cell models for the analysis: human, preadipocytes derived from adipose (visceral and subcutaneous) tissues and murine 3T3-L1 fibroblasts. We demonstrated a significant increase in the IL10 expression level, IL10 promoter region methylation, and histone 3 epigenetic modifications: H3K4me and H3K9/14ac, in insulin resistance cells (IR) from SAT cell culture. In IR cells from VAT cell culture, we observed decreased IL10 expression with a simultaneous increase of IL10 promoter region methylation. In IR cells from 3T3L1 cell culture, we observed the increased expression of IL10 as well as the decreased levels of methylation in the IL10 promoter region and histone methylation (H3K4me) and acetylation (H3K9/14ac). The presented analyses suggest a potential impact of epigenetic modifications on gene expression and a potential mutual influence of epigenetic modifications on each other or the activation of specific epigenetic regulation at a different stage of the development of insulin resistance in cells.

Endogenously produced catecholamines improve the regulatory function of TLR9-activated B cells

The sympathetic nervous system (SNS) contributes to immune balance by promoting anti-inflammatory B cells. However, whether B cells possess a self-regulating mechanism by which they modulate regulatory B cell (Breg) function is not well understood. In this study, we investigated the ability of B cells to synthesize their own catecholamines upon stimulation with different B cell activators and found that expression of the enzyme tyrosine hydroxylase (TH), required to generate catecholamines, is up-regulated by Toll-like receptor (TLR)9. This TLR9-dependent expression of TH correlated with up-regulation of adrenergic receptors (ADRs), enhanced interleukin (IL)-10 production, and overexpression of the co-inhibitory ligands programmed death ligand 1 (PD-L1) and Fas ligand (FasL). Moreover, concomitant stimulation of ß1-3-ADRs together with a B cell receptor (BCR)/TLR9 stimulus clearly enhances the anti-inflammatory potential of Bregs to suppress CD4 T cells, a crucial population in the pathogenesis of autoimmune diseases, like rheumatoid arthritis (RA). Furthermore, TH up-regulation was also demonstrated in B cells during the course of collagen-induced arthritis (CIA), a mouse model for the investigation of RA. In conclusion, our data show that B cells possess an autonomous mechanism to modulate their regulatory function in an autocrine and/or paracrine manner. These findings help to better understand the function of B cells in the regulation of autoimmune diseases and the interplay of SNS.

The sympathetic nervous system produces neurotransmitters such as catecholamines which contribute to immune balance by promoting anti-inflammatory B cells. This study shows that mouse B cells can themselves synthesize, sense, and transport catecholamines, which in turn modulate regulatory B cell function in an autocrine and/or paracrine manner to suppress T cell proliferation.

Targeting B cells in the pre-phase of systemic autoimmunity globally interferes with autoimmune pathology

Systemic lupus erythematosus (SLE) is characterized by a loss of self-tolerance, systemic inflammation, and multi-organ damage. While a variety of therapeutic interventions are available, it has become clear that an early diagnosis and treatment may be key to achieve long lasting therapeutic responses and to limit irreversible organ damage. Loss of humoral tolerance including the appearance of self-reactive antibodies can be detected years before the actual onset of the clinical autoimmune disease, representing a potential early point of intervention. Not much is known, however, about how and to what extent this pre-phase of disease impacts the onset and development of subsequent autoimmunity. By targeting the B cell compartment in the pre-disease phase of a spontaneous mouse model of SLE we now show, that resetting the humoral immune system during the clinically unapparent phase of the disease globally alters immune homeostasis delaying the downstream development of systemic autoimmunity.

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The clinically unapparent pre-phase of SLE impacts clinical disease

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Autoreactive IgM antibodies represent a biomarker for early therapeutic intervention

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Pre-phase B cells orchestrate clinical disease

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Depleting pre-phase B cells diminishes disease pathology

Immune Checkpoints in Pediatric Solid Tumors: Targetable Pathways for Advanced Therapeutic Purposes

The tumor microenvironment (TME) represents a complex network between tumor cells and a variety of components including immune, stromal and vascular endothelial cells as well as the extracellular matrix. A wide panel of signals and interactions here take place, resulting in a bi-directional modulation of cellular functions. Many stimuli, on one hand, induce tumor growth and the spread of metastatic cells and, on the other hand, contribute to the establishment of an immunosuppressive environment. The latter feature is achieved by soothing immune effector cells, mainly cytotoxic T lymphocytes and B and NK cells, and/or through expansion of regulatory cell populations, including regulatory T and B cells, tumor-associated macrophages and myeloid-derived suppressor cells. In this context, immune checkpoints (IC) are key players in the control of T cell activation and anti-cancer activities, leading to the inhibition of tumor cell lysis and of pro-inflammatory cytokine production. Thus, these pathways represent promising targets for the development of effective and innovative therapies both in adults and children. Here, we address the role of different cell populations homing the TME and of well-known and recently characterized IC in the context of pediatric solid tumors. We also discuss preclinical and clinical data available using IC inhibitors alone, in combination with each other or administered with standard therapies.

Invariant natural killer T cells balance B cell immunity

Invariant natural killer T (iNKT) cells mediate rapid immune responses which bridge the gap between innate and adaptive responses to pathogens while also providing key regulation to maintain immune homeostasis. Both types of important iNKT immune responses are mediated through interactions with innate and adaptive B cells. As such, iNKT cells sit at the decision-making fulcrum between regulating inflammatory or autoreactive B cells and supporting protective or regulatory B cell populations. iNKT cells interpret the signals in their environment to set the tone for subsequent adaptive responses, with outcomes ranging from getting licensed to maintain homeostasis as an iNKT regulatory cell (iNKT_reg ) or being activated to become an iNKT follicular helper (iNKT_FH ) cell supporting pathogen-specific effector B cells. Here we review iNKT and B cell cooperation across the spectrum of immune outcomes, including during allergy and autoimmune disease, tumor surveillance and immunotherapy, or pathogen defense and vaccine responses. Because of their key role as influencers, iNKT cells provide a valuable target for therapeutic interventions. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, depending on the circumstance.

Reading the room: iNKT cells influence B cell responses

Rapid immune responses regulated by invariant Natural Killer T (iNKT) cells bridge the gap between innate and adaptive responses to pathogens, while also providing key regulation to maintain immune homeostasis. iNKT immune protection and immune regulation are both mediated through interactions with innate and adaptive B cell populations that express CD1d. Recent studies have expanded our understanding of the position of iNKT cells at the fulcrum between regulating inflammatory and autoreactive B cells. Environmental signals influence iNKT cells to set the tone for subsequent adaptive responses, ranging from maintaining homeostasis as an iNKT regulatory cell (iNKT_reg) or supporting pathogen-specific effector B cells as an iNKT follicular helper (iNKT_FH). Here we review recent advances in iNKT and B cell cooperation during autoimmunity and sterile inflammation. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, across a range of indications.

Skin-Associated B Cells in the Pathogenesis of Cutaneous Autoimmune Diseases-Implications for Therapeutic Approaches

B lymphocytes are crucial mediators of systemic immune responses and are known to be substantial in the pathogenesis of autoimmune diseases with cutaneous manifestations. Amongst them are lupus erythematosus, dermatomyositis, systemic sclerosis and psoriasis, and particularly those driven by autoantibodies such as pemphigus and pemphigoid. However, the concept of autoreactive skin-associated B cells, which may reside in the skin and locally contribute to chronic inflammation, is gradually evolving. These cells are believed to differ from B cells of primary and secondary lymphoid organs and may provide additional features besides autoantibody production, including cytokine expression and crosstalk to autoreactive T cells in an antigen-presenting manner. In chronically inflamed skin, B cells may appear in tertiary lymphoid structures. Those abnormal lymph node-like structures comprise a network of immune and stromal cells possibly enriched by vascular structures and thus constitute an ideal niche for local autoimmune responses. In this review, we describe current considerations of different B cell subsets and their assumed role in skin autoimmunity. Moreover, we discuss traditional and B cell-associated approaches for the treatment of autoimmune skin diseases, including drugs targeting B cells (e.g., CD19- and CD20-antibodies), plasma cells (e.g., proteasome inhibitors, CXCR4 antagonists), activated pathways (such as BTK- and PI3K-inhibitors) and associated activator molecules (BLyS, APRIL).

CD28 Agonism Improves Survival in Immunologically Experienced Septic Mice via IL-10 Released by Foxp3+ Regulatory T Cells

Immune dysregulation during sepsis is mediated by an imbalance of T cell costimulatory and coinhibitory signaling. CD28 is downregulated during sepsis and is significantly altered on memory versus naive T cells. Thus, to study the role of CD28 during sepsis in a more physiologically relevant context, we developed a "memory mouse" model in which animals are subjected to pathogen infections to generate immunologic memory, followed by sepsis induction via cecal ligation and puncture. Using this system, we show that agonistic anti-CD28 treatment resulted in worsened survival in naive septic animals but conferred a significant survival advantage in immunologically experienced septic animals. Mechanistically, this differential response was driven by the ability of CD28 agonism to elicit IL-10 production from regulatory T cells uniquely in memory but not naive mice. Moreover, elevated IL-10 released by activated regulatory T cells in memory mice inhibited sepsis-induced T cell apoptosis via the antiapoptotic protein Bcl-xL. Together, these data demonstrate that immunologic experience is an important parameter that affects sepsis pathophysiology and can fundamentally change the outcome of modulating the CD28 pathway during sepsis. This study suggests that testing therapeutic strategies in immunologically experienced hosts may be one way to increase the physiologic relevance of rodent models in sepsis research.

Regulatory B cells and T cell Regulation in Cancer

Recent researches shed light on B cell role on various autoimmune diseases, including autoantibody-mediated diseases as well as T cell-mediated autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. B cells play a critical role in the immune response beyond the production of antibodies through mechanisms such as antigen presentation and cytokine production. Furthermore, B cells have recently been recognized to play a role in promoting tumor immunity against cancer. However, not all B cells positively regulate immune responses. Regulatory B cells negatively regulate immune responses by the production of anti-inflammatory cytokines such as interleukin (IL)-10, IL-35, and transforming growth factor-beta. Thus, a balance between effector and regulatory B cells regulates the immune response through the release of cytokines. In this review, we highlight the main emerging roles of B cells in tumor immunity with a focus on the T cell response. These findings can guide a protocol for selectively depleting regulatory B cells as a potential therapeutic strategy for patients with cancer.

Immune modulation by chronic exposure to waterpipe smoke and immediate-early gene regulation in murine lungs

OBJECTIVE

We investigated the effects of chronic waterpipe (WP) smoke on pulmonary function and immune response in a murine model using a research-grade WP and the effects of acute exposure on the regulation of immediate-early genes (IEGs).

METHODS

WP smoke was generated using three WP smoke puffing regimens based on the Beirut regimen. WP smoke samples generated under these puffing regimens were quantified for nicotine concentration. Mice were chronically exposed for 6 months followed by assessment of pulmonary function and airway inflammation. Transcriptomic analysis using RNAseq was conducted after acute exposure to characterise the IEG response. These biomarkers were then compared with those generated after exposure to dry smoke (without water added to the WP bowl).

RESULTS

We determined that nicotine composition in WP smoke ranged from 0.4 to 2.5 mg per puffing session. The lung immune response was sensitive to the incremental severity of chronic exposure, with modest decreases in airway inflammatory cells and chemokine levels compared with air-exposed controls. Pulmonary function was unmodified by chronic WP exposure. Acute WP exposure was found to activate the immune response and identified known and novel IEG as potential biomarkers of WP exposure.

CONCLUSION

Chronic exposure to WP smoke leads to immune suppression without significant changes to pulmonary function. Transcriptomic analysis of the lung after acute exposure to WP smoke showed activation of the immune response and revealed IEGs that are common to WP and dry smoke, as well as pools of IEGs unique to each exposure, identifying potential biomarkers specific to WP exposure.

Abnormal expression of b10 cell frequencies: possible relation to pathogenesis and disease severity of aplastic anemia

OBJECTIVE

Aplastic anemia (AA) is an immune-mediated disease that destroys hematopoietic cells through activated T lymphocytes. B lymphocyte-mediated humoral immunity also plays an important role in the pathogenesis of AA. Regulatory B cell (Breg) subpopulation, which is defined as "B10", secretes interleukin 10 (IL-10). The objective of our experiment was to investigate whether the scale-down proportion of B10 cells in AA patients may play a key role in the pathogenesis.

METHODS

A total of 38 AA patients (14 SAA patients and 24 NSAA patients) and 20 healthy control subjects were included. All subjects did not suffer from autoimmune diseases or any other diseases affecting the immune system, such as infectious diseases. Bone marrow mononuclear cells (PBMCs) were isolated and analyzed by Flow cytometry (FCM) and Immunofluorescence double-labeling assay. The relationship between the relative proportions of B10 and ProB10 and their associations to AA, as well as disease severity, were assessed by common clinical indicators and then examined.

RESULTS

Our analyses revealed AA patients had significantly lower proportions of peripheral B10 and B10pro compared to healthy controls. SAA patients had a substantially lower percentage of B10 cells and B10pro cells compared to NSAA patients. In addition, B10 cells and B10pro cells were negatively correlated with absolute neutrophil counts, hemoglobin levels and platelet, and absolute reticulocyte counts in AA patients.

CONCLUSIONS

The present study attempted to elucidate the potential role of the scale-down proportion of B10 cells in the pathogenesis of AA.

Regulatory B cells in myasthenia gravis are differentially affected by therapies

We analyzed the number and functionality of regulatory B (Breg) cells in well‐defined myasthenia gravis patients. We first showed a decreased number of circulating CD19⁺CD24⁺⁺CD38⁺⁺ Breg cells and an altered functionality of Breg cells in untreated myasthenia gravis patients. Next, we demonstrated that the proportion of circulating Breg cells was restored in myasthenia gravis patients after thymectomy, probably as Breg cells could be sequestered in the myasthenia gravis thymus. In contrast, corticosteroid treatments did not restore and decreased even more the proportion of Breg cells in myasthenia gravis patients. These results clearly demonstrated that two distinct immunomodulatory therapies affect differentially Breg cells.

Sialylated Autoantigen-Reactive IgG Antibodies Attenuate Disease Development in Autoimmune Mouse Models of Lupus Nephritis and Rheumatoid Arthritis

Pro- and anti-inflammatory effector functions of IgG antibodies (Abs) depend on their subclass and Fc glycosylation pattern. Accumulation of non-galactosylated (agalactosylated; G0) IgG Abs in the serum of rheumatoid arthritis and systemic lupus erythematosus (SLE) patients reflects severity of the diseases. In contrast, sialylated IgG Abs are responsible for anti-inflammatory effects of the intravenous immunoglobulin (pooled human serum IgG from healthy donors), administered in high doses (2 g/kg) to treat autoimmune patients. However, whether low amounts of sialylated autoantigen-reactive IgG Abs can also inhibit autoimmune diseases is hardly investigated. Here, we explore whether sialylated autoantigen-reactive IgG Abs can inhibit autoimmune pathology in different mouse models. We found that sialylated IgG auto-Abs fail to induce inflammation and lupus nephritis in a B cell receptor (BCR) transgenic lupus model, but instead are associated with lower frequencies of pathogenic Th1, Th17 and B cell responses. In accordance, the transfer of small amounts of immune complexes containing sialylated IgG Abs was sufficient to attenuate the development of nephritis. We further showed that administration of sialylated collagen type II (Col II)-specific IgG Abs attenuated the disease symptoms in a model of Col II-induced arthritis and reduced pathogenic Th17 cell and autoantigen-specific IgG Ab responses. We conclude that sialylated autoantigen-specific IgG Abs may represent a promising tool for treating pathogenic T and B cell immune responses in autoimmune diseases.

Deficiency of IL-1 receptor antagonist suppresses IL-10-producing B cells in autoimmune arthritis in an IL-17/Th17-dependent manner

Rheumatoid arthritis (RA) is a systemic autoimmune disease with CD4⁺ T cell infiltration and hyperplasia of synovial tissues leading to progressive destruction of articular cartilage. In addition to the central role of T cells in the pathogenesis of RA, recent reports have suggested that B cells also contribute to RA. To explore the effects of interleukin (IL)-17 on B cell development and response in excess IL-1 signaling, we generated IL-17 and IL-1 receptor antagonist (IL-1Ra) double-deficient mice via backcrossing IL-17 knockout (KO) and IL-1RaKO mice. We studied the effect of IL-17 deficiency on antibody-producing B cells and regulatory B cells in IL-1RaKO mice. Excess IL-1 signal increased the frequency of B220⁺ IgG⁺ cells and plasma cells. It also promoted the production of immunoglobulins in vitro. Moreover, IL-17 deficiency significantly enhanced the frequency of regulatory IL-10-producing regulatory B cells in IL-1RaKO mice. IL-17 deficiency ameliorated disease symptoms of inflammatory arthritis in IL-1RaKO mice by suppressing the frequency of plasma cells and antibody production while enhancing the frequency of IL-10-producing B cells. These findings suggest that IL-17 can trigger an inflammatory immune reaction by activating antibody-producing B cells while suppressing immune regulatory B cells in RA.

Targeting B Cells and Plasma Cells in Autoimmune Diseases

Success with B cell depletion using rituximab has proven the concept that B lineage cells represent a valid target for the treatment of autoimmune diseases, and has promoted the development of other B cell targeting agents. Present data confirm that B cell depletion is beneficial in various autoimmune disorders and also show that it can worsen the disease course in some patients. These findings suggest that B lineage cells not only produce pathogenic autoantibodies, but also significantly contribute to the regulation of inflammation. In this review, we will discuss the multiple pro- and anti-inflammatory roles of B lineage cells play in autoimmune diseases, in the context of recent findings using B lineage targeting therapies.

MicroRNAs 15A and 16-1 Activate Signaling Pathways That Mediate Chemotaxis of Immune Regulatory B cells to Colorectal Tumors

BACKGROUND & AIMS

B cells infiltrate tumors, but little is known about how they affect tumor growth and progression. microRNA15A (MIR15A or miRNA15A) and microRNA16-1 (MIR16-1 or miRNA16-1) regulate cell proliferation, apoptosis, and drug resistance. We investigated their involvement in B-cell-mediated immune suppression by colorectal tumors.

METHODS

Mice with disruptions of the gene cluster that encodes MIR15A and MIR16-1 (knockout mice), and control (C57BL/B6) mice were given azoxymethane with dextran sodium sulfate (AD) to induce formation of colorectal tumors. Mice were given anti-CD20 to delete B cells, or injections of agomir to increase MIR15A and MIR16-1. Proliferation of CD8⁺T cells was measured by carboxyfluorescein-succinimidyl-ester analysis. Colon tissues were collected from mice and analyzed by flow cytometry, microRNA (miRNA) sequencing, and for cytokine production. Intestinal epithelial cells (IECs) were isolated and transfected with miRNA mimics, to identify their targets. We analyzed miRNA expression patterns and quantified B cells in colorectal cancer tissue microarrays derived from 90 patients who underwent surgical resection, from July 2006 through April 2008, in Shanghai, China; expression data were compared with clinical outcomes.

RESULTS

Tumors that developed in knockout mice following administration of AD were larger and contained greater numbers of B cells than tumors that grew in control mice. Most of the B cells in the tumors were positive for immunoglobulin A (IgA⁺). IgA⁺ B cells expressed high levels of immune regulatory molecules (programmed death ligand 1, interleukin 10, and transforming growth factor beta), and repressed the proliferation and activation of CD8⁺ T cells. Levels of MIR15A and MIR16-1 were reduced in colon tumors from mice, compared with nontumor colon tissue. Incubation of IECs with IL17A reduced expression of MIR15A and MIR16-1. Transgenic expression of MIR15A and MIR16-1 in IECs decreased activation of NF-κB and STAT1 by reducing expression of I-kappaB kinases; this resulted in reduced production of chemokine (C-X-C motif) ligands 9 and 10 and decreased chemotaxis of IgA⁺ B cells. Tumors in mice injected with AD and agomir grew more slowly than tumors in mice not given in agomir and contained fewer IgA⁺ B cells. We found a negative correlation between levels of MIR15A and MIR16-1 and numbers of IgA⁺B cells in human colorectal tumor tissues; high levels of MIR15A and MIR16-1 and low numbers of IgA⁺B cells were associated with longer survival times of patients.

CONCLUSIONS

We found increased levels of MIR15A and MIR16-1 to reduce numbers of IgA⁺ B cells in colorectal tumor tissues and correlate with increased survival time of patients. In mice that lack MIR15A and MIR16-1, colon tumors grow more rapidly and contain increased numbers of IgA⁺ B cells. MIR15A and MIR16-1 appear to activate signaling pathways required for B-cell-mediated immune suppression.

Regulatory and Memory B Lymphocytes in Children With Newly Diagnosed Immune Thrombocytopenia

Background

Immune (idiopathic) thrombocytopenic purpura (ITP) is a primary autoimmune disease. It is characterized by a diminished peripheral platelet count (< 100 × 10⁹/L) caused by platelet destruction with an increased risk of mucocutaneous bleeding. The diagnosis of ITP depends on clinical characteristics and the laboratory examinations conducted, as well as the ability to exclude other diseases associated with thrombocytopenia. Antiplatelet autoantibodies are responsible for platelet destruction and probably for inhibition of megakaryopoiesis. B lymphocytes participate in immune responses through production of antibodies, antigen presentation to T cells, and cytokine secretion. The aims of this study were to investigate the levels of Bregs and memory B lymphocytes in newly diagnosed pediatric ITP patients and to correlate their levels with the course of the disease.

Methods

This study was a case-control study. The study included 30 patients with acute ITP. The patients were recruited from Pediatric Clinical Hematology Unit of Children Hospital, Assiut University. In addition, 20 healthy children of comparable age and sex were taken as controls. The institutional review board approved the study and informed consents were obtained.

Results

There is a significant alteration of B-cell homeostasis in patients with ITP.

Conclusion

Analysis of Bregs and memory B cells could serve as prognostic markers and might guide therapy in ITP patients in the future.

Transparent Substrates Prepared From Different Amorphous Polymers Can Directly Modulate Primary Human B cell functions

Manipulation of B cell functions such as antibody and cytokine secretion, is of clinical and biotechnological interest and can be achieved by soluble ligands activating cell surface receptors. Alternatively, the exposure to suitable solid substrates would offer the possibility to transiently induced cell signaling, since the signaling is interrupted when the cells are removed from the substrate. Cell/substrate interactions are mediated by physical valences such as, hydrogen bonds or hydrophobic forces on the substrate surface. Therefore, in this study B cells were cultivated on polymeric substrates, differing in their chemical composition and thus their capacity to undergo physical interactions. Activated B cells cultivated on polystyrene (PS) showed an altered cytokine response indicated by increased IL-10 and decreased IL-6 secretion. Interestingly, B cells cultivated on polyetherurethane (PEU), which has among all tested polymers the highest potential to form strong hydrogen bonds showed an impaired activation, which could be restored by re-cultivation on tissue culture polystyrene. The results indicate that B cell behavior can transiently be manipulated solely by interacting with polymeric surface, which could be explained by receptor activation mediated by physical interaction with the substrate or by altering the availability of the soluble stimulatory reagents by adsorption processes.

Inflammatory Conditions Dictate the Effect of Mesenchymal Stem or Stromal Cells on B Cell Function

The immunomodulatory capacity of mesenchymal stem or stromal cells (MSC) makes them a promising tool for treatment of immune disease and organ transplantation. The effects of MSC on B cells are characterized by an abrogation of plasmablast formation and induction of regulatory B cells (Bregs). It is, however, unknown how MSC interact with B cells under inflammatory conditions. In this study, adipose tissue-derived MSC were pretreated with 50 ng/ml IFN-γ for 96 h (MSC–IFN-γ) to simulate inflammatory conditions. Mature B cells were obtained from spleens by CD43⁻ selection. B cells were co-cultured with MSC and stimulated with anti-IgM, anti-CD40, and IL-2; and after 7 days, B cell proliferation, phenotype, Immunoglobulin-G (IgG), and IL-10 production were analyzed. MSC did not inhibit B cell proliferation but increased the percentage of CD38^high CD24^high B cells (Bregs) and IL-10 production, while MSC–IFN-γ significantly reduced B cell proliferation and inhibited IgG production by B cells in a more potent fashion but did not induce Bregs or IL-10 production. Both MSC and MSC–IFN-γ required proximity to target cells and being metabolically active to exert their effects. Indoleamine 2,3 dioxygenase expression was highly induced in MSC–IFN-γ and was responsible of the anti-proliferative and Breg reduction since addition of tryptophan (TRP) restored MSC properties. Immunological conditions dictate the effect of MSC on B cell function. Under immunological quiescent conditions, MSC stimulate Breg induction; whereas, under inflammatory conditions, MSC inhibit B cell proliferation and maturation through depletion of TRP. This knowledge is useful for customizing MSC therapy for specific purposes by appropriate pretreatment of MSC.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

B cells inhibit the antitumor immunity against an established murine fibrosarcoma

Despite the classic role of B cells in favoring the immune response, an inhibitory action of B lymphocytes in tumor immunity has emerged in certain studies. In methylcolanthrene-induced murine fibrosarcoma (MCC), the loss of immunogenicity and the establishment of tolerance are paralleled by systemic immune suppression and the appearance of B⁺IL-10⁺ cells in tumor-draining lymph nodes. The present study aimed to assess the role of the B⁺IL-10⁺ cell population in the immune evasion and tolerance induced by MCC through the depletion of B cells in mice at various times of tumor progression: Prior to or subsequent to tumor implantation. Tumor growth and immunological parameters were evaluated. B cell depletion prior to tumor inoculum enhanced tumor growth, initiating the onset of the tumor-induced systemic immune response; however, an increase in the T regulatory cells (Tregs) at the tumor-draining lymph node could account for tumor exacerbation. B cell depletion once the tumor was established resulted in decreased tumor growth and a delayed onset of tolerance. Additionally, B cell absence exacerbated T cell dependent-tumor rejection, reduced Tregs and increased cytotoxic CD8⁺ T cells. In vitro analysis showed a direct effect of B cells upon T cell proliferation. In conclusion, B cell depletion exerts opposite effects when performed prior to or subsequent to tumor implantation. In this initially immunogenic tumor, B cell absence would delay the establishment of immunological tolerance probably by unmasking a pre-existing antitumor response. The present findings elucidate the convenience of modulating B cells in the development of future and more effective immunotherapies against cancer.

Significance of B10 cell in patients with thymoma complicated with myasthenia gravis

A subset of regulatory B cells in humans has been identified as B10 cell which has the function of secreting interleukin-10. We evaluated the significance of B10 cell in patients with thymoma complicated with myasthenia gravis. In this study, 156 patients diagnosed with thymoma were enrolled, FCM was used to detected the percentage of Breg/CD19⁺B cells and CD19⁺B cells/PBMC, ELISA to evaluate the serum concentration of the relevant immunological markers; purified CD19⁺B cells in tissues by MACS; gene and protein expressions of CD19 and IL-10 by Real-time PCR and Western-Blot; double immunofluorescence staining to detect the distribution of CD19 and IL-10 in thymus tissues. Thymoma patients without MG mainly display the types A and AB of thymoma, whereas the thymoma patients with MG mainly display type B (B1, B2 and B3) thymoma; AChR-Ab in Tm + MG group was the highest, with the progress of the disease, the percentage of Breg/CD19⁺B cells increased and B10/CD19⁺B cells decreased (p < 0.05); ROC curve showed that B10 had the greatest significance for the clinical directivity of Tm+MG and cut-off point = 0.55%; in accordance with the Con, Tm and Tm+MG group, the content of CD19⁺IL-10⁺B10 cells increased gradually (p < 0.05); meanwhile, the gene and protein expression levels of CD19 and IL-10 gradually increased in the same way. It is concluded that with the progress of thymoma, the infiltration of Breg in tumour tissue increases; however, as the severity of MG increases, the function of Breg (B10 cell) in peripheral blood decreases and the cut-off point is 0.55%.

What do we know about the role of regulatory B cells (Breg) during the course of infection of two major parasitic diseases, malaria and leishmaniasis?

Parasitic diseases, such as malaria and leishmaniasis, are relevant public health problems worldwide. For both diseases, the alarming number of clinical cases and deaths reported annually has justified the incentives directed to better understanding of host's factors associated with susceptibility to infection or protection. In this context, over recent years, some studies have given special attention to B lymphocytes with a regulator phenotype, known as Breg cells. Essentially important in the maintenance of immunological tolerance, especially in autoimmune disease models such as rheumatoid arthritis and experimentally induced autoimmune encephalomyelitis, the function of these lymphocytes has so far been poorly explored during the course of diseases caused by parasites. As the activation of Breg cells has been proposed as a possible therapeutic or vaccine strategy against several diseases, here we reviewed studies focused on understanding the relation of parasite and Breg cells in malaria and leishmaniasis, and the possible implications of these strategies in the course of both infections.

Dual genetic absence of STAT6 and IL-10 does not abrogate anti-hyperglycemic effects of Schistosoma mansoni in streptozotocin-treated diabetic mice

Schistosoma mansoni (Sm) is known to exert protective effects against various allergic and autoimmune disorders. It has been reported that this parasite protects NOD mice from spontaneous type 1 diabetes (T1D) and ameliorates streptozotocin (STZ)-induced T1D in wild-type mice. Here, we tried to clarify the anti-diabetic mechanisms of Sm in the latter model. Sm infection partially prevented the degradation of pancreatic islets and hyperglycemia in multiple low-dose (MLD) STZ-treated mice. Neither Treg cell depletion nor genetic absences of IL-10 and/or STAT6 abrogated the anti-hyperglycemic effects of Sm. Among M2 macrophage markers, Arg-1 and Ym1, but not Retnla, remained up-regulated in the pancreatic lymph nodes and in the spleens of STAT6/IL-10 double deficient (DKO) mice. Collectively, it is suggested that Sm exerts anti-diabetic effects on this experimental T1D model via Treg/IL-4/IL-13/IL-10-independent mechanisms. Augmented expressions of Arg-1 and Ym1 in the lymphoid organs adjacent to pancreas may be relevant to the anti-diabetic effects of Sm.

Regulatory B Cells in Seropositive Myasthenia Gravis versus Healthy Controls

OBJECTIVE

To find out if the failure in immunotolerance of myasthenia gravis (MG) is a possible aspect of deduction in Breg cells and to characterize B cell subsets in MG.

METHODS

Flow cytometry detection and enzyme-linked immunosorbent assays in peripheral blood films of 10 MG patients and 10 healthy controls (HCs) were performed after isolation of B cells. The CD19⁺CD5⁺CD1d⁺ Breg cells percentages were measured to complement a B cell phenotype assay and frequencies of B cell subsets. The clinical outcome measures and immunological variables of patients with MG were compared with HCs.

RESULTS

Patients with MG had relatively lowered percentages of CD19⁺CD5⁺CD1d⁺ Breg cells as compared to HCs. The production of interleukin (IL)-10 and transforming growth factor (TGF)-β1 was relatively lesser in patients with MG than HCs, which were linked with more severe of MG disease status according to Myasthenia Gravis Foundation of America (MGFA) clinical classification. The reduction of cytokine production was more significant for IL-10 than TGF-β1 when compared to HCs.

CONCLUSION

It has been observed that the reduced number of B cells is able to produce IL-10 in MG patients but lesser than compared to HCs. The Bregs reduction mainly was regarded by the severity of disease status, which was highly significant and also by disease duration which was statistically significant as well. The findings of the measurement of B cell phenotype assay and frequencies of B cell subsets between MGs and HCs give us new ideas to develop B cell-mediated therapies of MG such as (1) isolated B cells of MGs could be cultured with steroids, e.g., dexamethasone in vitro to see if it induces the CD19⁺CD5⁺CD1d⁺ Breg cells, (2) it may observe whether induced CD19⁺CD5⁺CD1d⁺ Bregs have higher production of IL-10 and TGF-β1, as both are linked with disease severity, and (3) after completion in vitro steps, through further research in vivo to observe whether it improves the function of MG disease status.

IL-10-Producing CD1dhiCD5+ Regulatory B Cells May Play a Critical Role in Modulating Immune Homeostasis in Silicosis Patients

Silicosis is characterized by chronic lung inflammation and fibrosis, which are extremely harmful to human health. The pathogenesis of silicosis involves uncontrolled immune processes. Evidence supports that regulatory B cells (Bregs) produce negative regulatory cytokines, such as IL-10, which can negatively regulate immune responses in inflammation and autoimmune diseases. Our previous study found that IL-10-producing B cells were involved in the development of silica-induced lung inflammation and fibrosis of mice. However, little is known about the role of Bregs in silicosis patients (SP). In this study, we found that serum concentrations of IL-10 were significantly increased in SP by using protein array screening. We further determined that the frequency of IL-10-producing CD1d^hiCD5⁺ Bregs, not IL-10-producing non-B lymphocytes, was significantly higher in SP compared to subjects under surveillance (SS) and healthy workers (HW) by flow cytometry. We also found that regulatory T cells (Tregs) and Th2 cytokines (IL-4, IL-5, and IL-13) were significantly increased in SP. Th1 cytokines (IFN-γ, IL-2, and IL-12) and inflammatory cytokines (IL-1β, IL-6, and TNF-α) were not significantly different between SP, SS, and HW. Our study indicated that IL-10-producing CD1d^hiCD5⁺ Bregs might maintain Tregs and regulate Th1/Th2 polarization in SP, suggesting that IL-10-producing Bregs may play a critical role in modulating immune homeostasis in SP.

Activation of human B cells negatively regulates TGF-β1 production

BACKGROUND

Accumulating evidence indicate that B cells can exhibit pro- or anti-inflammatory activities. Similar to interleukin (IL)-10-competent B cells, we recently showed that transforming growth factor (TGF)-β1-producing regulatory B cells limit the induction of autoimmune neuroinflammation in mice, making them potentially important in maintaining peripheral immune tolerance in central nervous system inflammatory demyelinating disorders such as multiple sclerosis.

METHODS

In this study, we compared B cell production of TGF-β1 and IL-10, the two most studied regulatory cytokines, and the pro-inflammatory B cell-derived IL-6 and tumor necrosis factor cytokines under basal conditions and following polyclonal stimulation with dual B cell receptor (BCR) cross-linking and Toll-like receptor (TLR)9 engagement.

RESULTS

We showed that resting TGF-β1-producing B cells fall within both the naïve (CD27^-) and memory (CD27⁺) B cell compartments. We found no spontaneous B cell-derived IL-10, IL-6 or tumor necrosis factor (TNF) production. Human B cell activation with anti-Ig antibodies plus CPG-B leads to only modest IL-10 production by memory CD19⁺CD27⁺ B cells while expression levels of IL-6 and TNF by both naive and memory B cells were strongly induced. Remarkably, stimulated B cells showed significantly reduced capacity to produce TGF-β1.

CONCLUSIONS

These findings indicate that B cell activation may facilitate the development of excessive immune responses and autoimmunity by restricting B cell-derived TGF-β1 production by resting B cells and favoring in turns the proinflammatory actions of activated cytokine-producing B cells.

Induction and Differentiation of IL-10-Producing Regulatory B Cells from Healthy Blood Donors and Rheumatoid Arthritis Patients

The most important feature of B cells is the production of Abs upon activation; additionally, B cells produce pro- and anti-inflammatory cytokines in response to certain stimuli. IL-10-producing B cells represent a major subset of regulatory B cells (Bregs) that suppress autoimmune and inflammatory responses. B cells play a crucial role in the development and maintenance of the chronic inflammatory autoimmune disease rheumatoid arthritis (RA); however, controversial data are available on IL-10- producing Bregs in RA. Our aim was to identify the optimal conditions that induce IL-10⁺ Bregs and, furthermore, to shed light on the signaling pathways that are responsible for their expansion. The results show that dual stimulation by CpG and CD40L for 48 h is optimal for IL-10 induction, and this can be synergistically boosted by IL-21. We identified the CD19⁺CD27⁺ memory B cell population as the major source of IL-10⁺ Bregs. We detected significantly fewer CD19⁺CD27⁺IL-10⁺ cells in RA patients compared with healthy controls, and these were functionally defective in suppressing IFN-γ production by CD4⁺ T cells in coculture. IL-21 drastically increased the number of IL-10⁺ Bregs within the CD19⁺CD27⁺ and CD19⁺CD27^- populations; furthermore, it induced the appearance of IL-10⁺Blimp-1⁺ plasmablasts. Monitoring the phosphorylation of key signaling molecules revealed that activation of ERK, p38, and CREB is indispensable for the induction of IL-10 production, whereas phosphorylation of STAT3 further enhances IL-10 expression in human Bregs. We conclude that CREB and STAT3 are the key transcription factors responsible for the expansion and differentiation of human IL-10-producing Bregs.

Lymphoid Neogenesis and Tertiary Lymphoid Organs in Transplanted Organs

The progressive organization of immune effectors into functional ectopic lymphoid structures, named tertiary lymphoid organs (TLO), has been observed in many conditions in which target antigens fail to be eliminated by the immune system. Not surprisingly, TLO have been recurrently identified in chronically rejected allografts. Although significant progress has been made over the last decades in understanding the molecular mechanisms involved in TLO development (a process named lymphoid neogenesis), the role of intragraft TLO (if any) in chronic rejection remains elusive. The prevailing dogma is that TLO contribute to graft rejection by generating and propagating local humoral and cellular alloimmune responses. However, TLO have been recently observed in long-term accepting allografts, suggesting that they might also be able to regulate alloimmune responses. In this review, we discuss our current understanding of how TLO are induced and propose a unified model in which TLO can play deleterious or regulatory roles and therefore actively modulate the kinetics of chronic rejection.

MicroRNA-98 plays a critical role in experimental myocarditis

BACKGROUND AND AIMS

Myocarditis is inflammation in the heart; its pathogenesis is to be further investigated. Activities of micro RNAs (miR) are associated with immune inflammation. This study tests a hypothesis that miR-98 is involved in the development of myocarditis.

METHODS

BALB/c mice were immunized with cardiac α-myosin heavy chain peptides (MyHC-α) to induce myocarditis. The effects of miR-98 on regulation of interleukin (IL)-10 were assessed by real time RT-PCR.

RESULTS

Mice immunized with MyHC-α showed myocarditis and lower frequency of IL-10⁺ B cells (B10 cell) in the hearts. Expression of miR-98 was higher, IL-10 was lower, in B cells isolated from the mouse hearts with myocarditis, which was negatively correlated with each other. Exposure to tumor necrosis factor-α up regulated miR-98 expression in B cells. Over-expression of miR-98 suppressed IL-10 expression in B cells. Blocking miR-98 or adoptively transplanting B10 cells attenuated experimental myocarditis.

CONCLUSIONS

miR-98 suppresses IL-10 expression in B cells in the heart, which plays an important role in myocarditis. MiR-98 may be a therapeutic target in the treatment of myocarditis.

Altered Interleukin-10 Signaling in Skeletal Muscle Regulates Obesity-Mediated Inflammation and Insulin Resistance

Skeletal muscle insulin resistance is a major characteristic of obesity and type 2 diabetes. Although obesity-mediated inflammation is causally associated with insulin resistance, the underlying mechanism is unclear. Here, we examined the effects of chronic obesity in mice with muscle-specific overexpression of interleukin-10 (M^IL10). After 16 weeks of a high-fat diet (HFD), M^IL10 mice became markedly obese but showed improved insulin action compared to that of wild-type mice, which was largely due to increased glucose metabolism and reduced inflammation in skeletal muscle. Since leptin regulates inflammation, the beneficial effects of interleukin-10 (IL-10) were further examined in leptin-deficient ob/ob mice. Muscle-specific overexpression of IL-10 in ob/ob mice (MCK-IL10^ob/ob) did not affect spontaneous obesity, but MCK-IL10^ob/ob mice showed increased glucose turnover compared to that in ob/ob mice. Last, mice with muscle-specific ablation of IL-10 receptor (M-IL10R^-/-) were generated to determine whether IL-10 signaling in skeletal muscle is involved in IL-10 effects on glucose metabolism. After an HFD, M-IL10R^-/- mice developed insulin resistance with reduced glucose metabolism compared to that in wild-type mice. Overall, these results demonstrate IL-10 effects to attenuate obesity-mediated inflammation and improve insulin sensitivity in skeletal muscle, and our findings implicate a potential therapeutic role of anti-inflammatory cytokines in treating insulin resistance and type 2 diabetes.

B cell-derived transforming growth factor-β1 expression limits the induction phase of autoimmune neuroinflammation

Studies in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), have shown that regulatory B cells modulate the course of the disease via the production of suppressive cytokines. While data indicate a role for transforming growth factor (TGF)-β1 expression in regulatory B cell functions, this mechanism has not yet been tested in autoimmune neuroinflammation. Transgenic mice deficient for TGF-β1 expression in B cells (B-TGF-β1^-/-) were tested in EAE induced by recombinant mouse myelin oligodendrocyte glycoprotein (rmMOG). In this model, B-TGF-β1^-/- mice showed an earlier onset of neurologic impairment compared to their littermate controls. Exacerbated EAE susceptibility in B-TGF-β1^-/- mice was associated with augmented CNS T helper (Th)1/17 responses. Moreover, selective B cell TGF-β1-deficiency increased the frequencies and activation of myeloid dendritic cells, potent professional antigen-presenting cells (APCs), suggesting that B cell-derived TGF-β1 can constrain Th1/17 responses through inhibition of APC activity. Collectively our data suggest that B cells can down-regulate the function of APCs, and in turn encephalitogenic Th1/17 responses, via TGF-β1, findings that may be relevant to B cell-targeted therapies.

B Lymphocytes in Multiple Sclerosis: Bregs and BTLA/CD272 Expressing-CD19+ Lymphocytes Modulate Disease Severity

B lymphocytes contribute to the pathogenesis of Multiple Sclerosis (MS) by secreting antibodies and producing cytokines. This latter function was analyzed in myelin olygodendrocyte protein (MOG)-stimulated CD19+ B lymphocytes of 71 MS patients with different disease phenotypes and 40 age-and sex-matched healthy controls (HC). Results showed that: 1) CD19+/TNFα+, CD19+/IL-12+ and CD19+/IFNγ+ lymphocytes are significantly increased in primary progressive (PP) compared to secondary progressive (SP), relapsing-remitting (RR), benign (BE) MS and HC; 2) CD19+/IL-6+ lymphocytes are significantly increased in PP, SP and RR compared to BEMS and HC; and 3) CD19+/IL-13+, CD19+/IL-10+, and CD19+/IL-10+/TGFβ+ (Bregs) B lymphocytes are reduced overall in MS patients compared to HC. B cells expressing BTLA, a receptor whose binding to HVEM inhibits TcR-initiated cytokine production, as well as CD19+/BTLA+/IL-10+ cells were also significantly overall reduced in MS patients compared to HC. Analyses performed in RRMS showed that fingolimod-induced disease remission is associated with a significant increase in Bregs, CD19+/BTLA+, and CD19+/BTLA+/IL-10+ B lymphocytes. B lymphocytes participate to the pathogenesis of MS via the secretion of functionally-diverse cytokines that might play a role in determining disease phenotypes. The impairment of Bregs and CD19+/BTLA+ cells, in particular, could play an important pathogenic role in MS.

New insights into B cell biology in systemic lupus erythematosus and Sjögren's syndrome

PURPOSE OF REVIEW

Our understanding of the physiological and pathogenic functions of B cells in systemic lupus erythematosus (SLE) and Primary Sjögren's syndrome (pSS) continues to expand. In this review, we discuss novel insights published in the last 18 months into the roles of B cells in systemic autoimmunity.

RECENT FINDINGS

Data have continued to expand regarding the diverse mechanisms by which innate immune signals including Toll-like receptors (TLRs) regulate the B cell compartment. Localized B cells and long-lived plasma cells have been identified as playing an important role in target tissue including the development of ectopic lymphoid structures in kidney and salivary gland. In addition to pathogenic roles for B cells, there is mounting evidence for regulatory B cell subsets that play a protective role and new insights into the signals that regulate their development.

SUMMARY

The past few years have provided insights into the multiple paths by which innate immune signals can lead to B cell activation in SLE and pSS and the increasingly diverse ways in which B cells contribute to disease expression. Further understanding the imbalance between protective and pathogenic functions for B cells in disease including in understudied target tissue should yield new treatment approaches.

Amelioration of autoimmune arthritis by adoptive transfer of Foxp3-expressing regulatory B cells is associated with the Treg/Th17 cell balance

BACKGROUND

Foxp3 is a key regulator of the development and function of regulatory T cells (Tregs), and its expression is thought to be T cell-restricted. We found that B cells in mice can express Foxp3 and B cells expressing Foxp3 may play a role in preventing the development of collagen-induced arthritis (CIA) in DBA/1J mice.

METHODS

Foxp3 expression was modulated in CD19(+) B cells by transfection with shRNA or using an over-expression construct. In addition, Foxp3-transfected B cells were adoptively transferred to CIA mice. We found that LPS or anti-IgM stimulation induced Foxp3 expression in B cells. Foxp3-expressing B cells were found in the spleens of mice.

RESULTS

Over-expression of Foxp3 conferred a contact-dependent suppressive ability on proliferation of responder T cells. Down-regulation of Foxp3 by shRNA caused a profound induction in proliferation of responder T cells. Adoptive transfer of Foxp3(+)CD19(+) B cells attenuated the clinical symptoms of CIA significantly with concomitant suppression of IL-17 production and enhancement of Foxp3 expression in CD4(+) T cells from splenocytes.

CONCLUSION

Our data indicate that Foxp3 expression is not restricted to T cells. The expression of Foxp3 in B cells is critical for the immunoregulation of T cells and limits autoimmunity in a mouse model.

Cutting Edge: Integrin α4 Is Required for Regulatory B Cell Control of Experimental Autoimmune Encephalomyelitis

The neutralization of integrin α4 (Itga4) is currently used as treatment in multiple sclerosis. Although most studies have focused on its function on lymphocyte migration to the CNS, we have uncovered the importance of Itga4 for the generation of regulatory B cells in peripheral immune organs and their control of pathogenic T cell response and CNS pathology. Our study underscores the importance of looking at the dual role of B cells in CNS autoimmunity and provides important perspectives regarding the efficacy and side effects associated with Itga4 neutralization and other B cell-targeting therapies.

A novel splenic B1 regulatory cell subset suppresses allergic disease through phosphatidylinositol 3-kinase-Akt pathway activation

BACKGROUND

IL-10-producing regulatory B (B10) cells potently suppress allergic diseases, such as contact hypersensitivity (CHS). Splenic B10 cells share overlapping phenotypic markers with CD5⁺ B1 B cells, CD1d^hiCD21⁺CD23^- marginal zone (MZ) B cells, and CD1d^hiCD21⁺CD23⁺ T2-MZ precursor B cells but do not exclusively belong to either subset.

OBJECTIVE

In this study we investigated the signaling mechanisms and a novel phenotypic parameter of B10 cells.

METHOD

We performed microarray analysis comparing IL-10⁺ and IL-10^- B cells. B cell-specific phosphatase and tensin homolog (PTEN)-deficient mice, which exhibit aberrant activation of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway in B cells, were examined.

RESULTS

Microarray analysis revealed that the PI3K-Akt pathway is important for IL-10 production in B cells. PI3K-Akt pathway inhibitors reduced B10 cell numbers in vitro. B10 cell numbers were significantly increased in B cell-specific PTEN-deficient mice. The CHS response was significantly diminished in PTEN-deficient mice. Unexpectedly, splenic B10 cells in these mice were found within the B1 B-cell subset but not within the MZ B-cell subset. In wild-type mice not only MZ B10 cells but also B1-B10 cells were identified in the spleen. In addition, these 2 B10 cell subsets were predominantly found within the CD9⁺CD80⁺ B-cell fraction.

CONCLUSION

A novel splenic B1 regulatory cell subset (B1-B10 cells) was identified. Our findings show that the PI3K-Akt pathway in B cells is critical for B10 cell development and CHS response and that CD9/CD80 coexpression is a novel phenotypic parameter for both MZ-B10 and B1-B10 cells.

Rapamycin prevents bronchiolitis obliterans through increasing infiltration of regulatory B cells in a murine tracheal transplantation model

OBJECTIVE

B lymphocytes are generally considered to be activators of the immune response; however, recent findings have shown that a subtype of B lymphocytes, regulatory B lymphocytes, play a role in attenuating the immune response. Bronchiolitis obliterans remains the major limitation to modern-day lung transplantation. The role of regulatory B lymphocytes in bronchiolitis obliterans has not been elucidated. We hypothesized that regulatory B lymphocytes play a role in the attenuation of bronchiolitis obliterans.

METHODS

We performed a standard heterotopic tracheal transplant model. Tracheas from Balb/c mice were transplanted into C57BL/6 recipients. Rapamycin treatment and dimethyl sulfoxide control groups were each treated for the first 14 days after the transplant. Tracheas were collected on days 7, 14, and 28 post-transplantation. Luminal obliteration was evaluated by hematoxylin-eosin staining and Picrosirius red staining. Immune cell infiltration and characteristics, and secretion of interleukin-10 and transforming growth factor-β1 were accessed by immunohistochemistry. Cytokines and transforming growth factor-β1 were measured using the Luminex assay (Bio-Rad, Hercules, Calif).

RESULTS

The results revealed that intraperitoneal injection of rapamycin for 14 days after tracheal transplantation significantly reduced luminal obliteration on day 28 when compared with the dimethyl sulfoxide control group (97.78% ± 3.63% vs 3.02% ± 2.14%, P < .001). Rapamycin treatment markedly induced regulatory B lymphocytes (B220(+)IgM(+)IgG(-)IL-10(+)TGF-β1(+)) cells when compared with dimethyl sulfoxide controls. Rapamycin treatment inhibited interleukin-1β, 6, 13, and 17 on days 7 and 14. Rapamycin also greatly increased interleukin-10 and transforming growth factor-β1 production in B cells and regulatory T lymphocytes infiltration on day 28.

CONCLUSIONS

Mammalian target of rapamycin inhibition decreases the development of bronchiolitis obliterans via inhibition of proinflammatory cytokines and increasing regulatory B lymphocytes cell infiltration, which subsequently produces anti-inflammatory cytokines and upregulates regulatory T lymphocyte cells.