Regulatory B cells (B10 cells) have a suppressive role in murine lupus: CD19 and B10 cell deficiency exacerbates systemic autoimmunity

Intracellular B Lymphocyte Signalling and the Regulation of Humoral Immunity and Autoimmunity

B lymphocytes are critical for effective immunity; they produce antibodies and cytokines, present antigens to T lymphocytes and regulate immune responses. However, because of the inherent randomness in the process of generating their vast repertoire of antigen-specific receptors, B cells can also cause diseases through recognizing and reacting to self. Therefore, B lymphocyte selection and responses require tight regulation at multiple levels and at all stages of their development and activation to avoid diseases. Indeed, newly generated B lymphocytes undergo rigorous tolerance mechanisms in the bone marrow and, subsequently, in the periphery after their migration. Furthermore, activation of mature B cells is regulated through controlled expression of co-stimulatory receptors and intracellular signalling thresholds. All these regulatory events determine whether and how B lymphocytes respond to antigens, by undergoing apoptosis or proliferation. However, defects that alter regulated co-stimulatory receptor expression or intracellular signalling thresholds can lead to diseases. For example, autoimmune diseases can result from altered regulation of B cell responses leading to the emergence of high-affinity autoreactive B cells, autoantibody production and tissue damage. The exact cause(s) of defective B cell responses in autoimmune diseases remains unknown. However, there is evidence that defects or mutations in genes that encode individual intracellular signalling proteins lead to autoimmune diseases, thus confirming that defects in intracellular pathways mediate autoimmune diseases. This review provides a synopsis of current knowledge of signalling proteins and pathways that regulate B lymphocyte responses and how defects in these could promote autoimmune diseases. Most of the evidence comes from studies of mouse models of disease and from genetically engineered mice. Some, however, also come from studying B lymphocytes from patients and from genome-wide association studies. Defining proteins and signalling pathways that underpin atypical B cell response in diseases will help in understanding disease mechanisms and provide new therapeutic avenues for precision therapy.

Regulatory B cells in autoimmune rheumatic diseases

Background:

Regulatory B cells (regulatory B cells, Breg cells) in recent years have been shown to be important immunoregulatory factors.

Aim:

To review the role of Breg cells in autoimmune rheumatic diseases.

Methods:

This descriptional review was carried out after research on PubMed using the keywords “Bregs and rheumatoid arthritis”, “systemic lupus erythematosus”, “Sjögren’s syndrome”, “systemic sclerosis”, “vasculitis”, and “dermatomyositis”.

Results:

Breg cells have an inhibitory effect on pro-inflammatory Th1 and Th17 cells and prevent the development of autoimmune diseases. Breg cells mediate their effects through interleukin-10 (IL-10, IL-10+Breg cells), but recently other Breg cells have been recognized that mediate their effects through IL-35 (IL-35+Breg cells), or through transforming growth factor-β (TGFβ, TGFβ+Breg cells). In experimental models of autoimmune diseases, Breg cells are decreased, and when expanded ex vivo and re-infused back into animals, they ameliorate disease. In humans, IL-10+Breg cells are decreased in active autoimmune diseases, such as rheumatoid arthritis, ANCA-associated vasculitis, and systemic sclerosis, and may increase to normal levels in disease remission.

Conclusions:

The deficiency of IL-10+Breg cells during active autoimmune rheumatic disease suggests that Breg cells may be used as biomarkers and be a possible therapeutic target in these diseases.

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.

TLR4 supports the expansion of FasL+CD5+CD1dhi regulatory B cells, which decreases in contact hypersensitivity

Certain B cells termed as "regulatory B cells" (Bregs) can suppress the ongoing immune responses and a splenic CD5⁺CD1d^hi Breg subset identified earlier was shown to exert its regulatory functions through secretion of IL-10. Though FasL expression is an alternative mechanism of immune suppression used by B cells, little is known about the FasL expressing CD5⁺CD1d^hi Bregs. In this study, we isolated splenocytes or splenic CD19⁺ B cells and compared the efficiency of toll-like receptor(TLR)4 ligand (lipopolysaccharide) with TLR9 ligand (CpG), anti-CD40 and TLR9 ligand (CpG) plus anti-CD40 on the FasL expression of splenic CD5⁺CD1d^hi Bregs by flow cytometry. FasL expression in CD5⁺CD1d^hi B cells was rapidly increased after TLR4 ligation. Intriguingly, anti-CD40 and CpG plus anti-CD40 combinations failed to stimulate FasL expression in CD5⁺CD1d^hi B cells although the IL-10 production was up-regulated in this subset. In addition, LPS and other B10-cell inducers increased the expression of surface molecules like CD86 and CD25, which are correlated to the regulatory functions of B cells. Furthermore, NF-κB and NF-AT inhibitors decreased the TLR4-activated FasL expression in CD5⁺CD1d^hi B cells. Then we sorted splenic CD5⁺CD1d^hi Bregs using flow cytometry and found that TLR4-activated CD5⁺CD1d^hi Bregs suppressed the proliferation of CFSE-labeled CD4⁺ T cells in vitro, which was partly blocked by anti-FasL antibody. In oxazolone-sensitized mice having contact hypersensitivity, FasL expression in splenic CD5⁺CD1d^hi B cells was decreased compared to the control group after TLR4 ligation. Our findings suggest that the regulatory function of CD5⁺CD1d^hi B cells could be partly mediated by Fas-FasL pathway and this FasL expressing CD5⁺CD1d^hi Bregs might participate in the regulation of inflammatory diseases.

Decreased CD1d level is associated with CD86 over-expression in B cells from systemic lupus erythematosus

The disorder of B cells is one of the hallmarks of systemic lupus erythematosus (SLE). The activation state indicated by CD86 of B cells from SLE is well known, while the defect of regulatory B cells mediated by CD1d is also responsible for the process of SLE. In the present study, we focused on the relationship between B cell activation mediated by CD86 and B cell regulatory function mediated by CD1d. Our results showed that the level of CD1d in B cells was decreased during the early stages of B6.MRLlpr SLE mice and imiquimod-treated (IMQ-treated) mice, while the level of CD86 was significantly increased at the late stage. Moreover, the expression of CD1d showed a significantly negative correlation with CD86 level in B cells from IMQ-treated mice (r = -05741; P = 0.0022), B6.MRLlpr mice (r = -0.7091; P = 0.0268), and SLE patients (r = -0.4125; P = 0.0404). The in vivo and in vitro experiments with splenocytes demonstrated that CD1d signaling pathway could inhibit toll-like receptor 7 (TLR7)-induced CD86 expression of B cells. Further studies showed that this relationship also affected antibody production. Thus, our results confirmed the association of CD1d and CD86 levels in B cells from SLE, and demonstrated the importance to preserve the immunoregulatory function of B cells mediated by CD1d in the progression of SLE.

Regulatory B cells: Phenotype, function and role in transplantation

While B cells are traditionally known for their roles in antibody production, antigen presentation and cytokine production, recent studies have highlighted the existence of B cells with regulatory properties, which have been termed Bregs, analogous to regulatory T cells (Tregs). Bregs have been found to play a role in autoimmune disease, malignancies, infections, and may also be involved in solid organ transplantation. Their main mechanism of action is by promoting the development of Tregs while suppressing effector CD4⁺ and CD8⁺ T cells, primarily by IL-10 secretion. In the field of transplantation evidence for an active role of Bregs is scarce. While the presence of Bregs has been associated with improved graft survival and operational tolerance in kidney transplant recipients, these findings are not without controversy. Since the majority of fundamental research on Bregs has been performed in the fields in autoimmunity and infectious diseases, we will first focus on what these fields taught us on basic Breg biology, after which the relevance for the transplant setting is discussed.

Regulatory B Cells in Pregnancy: Lessons from Autoimmunity, Graft Tolerance, and Cancer

The success of pregnancy is contingent on the maternal immune system recognizing and accommodating a growing semi-allogeneic fetus. Specialized subsets of lymphocytes capable of negative regulation are fundamental in this process, and include the regulatory T cells (Tregs) and potentially, regulatory B cells (Bregs). Most of our current understanding of the immune regulatory role of Bregs comes from studies in the fields of autoimmunity, transplantation tolerance, and cancer biology. Bregs control autoimmune diseases and can elicit graft tolerance by inhibiting the differentiation of effector T cells and dendritic cells (DCs), and activating Tregs. Furthermore, in cancer, Bregs are hijacked by neoplastic cells to promote tumorigenesis. Pregnancy therefore represents a condition that reconciles these fields-mechanisms must be in place to ensure maternal immunological tolerance throughout gravidity to allow the semi-allogeneic fetus to grow within. Thus, the mechanisms underlying Breg activities in autoimmune diseases, transplantation tolerance, and cancer may take place during pregnancy as well. In this review, we discuss the potential role of Bregs as guardians of pregnancy and propose an endocrine-modulated feedback loop highlighting the Breg-Treg-tolerogenic DC interface essential for the induction of maternal immune tolerance.

B10 Cell Frequencies and Suppressive Capacity in Myasthenia Gravis Are Associated with Disease Severity

Myasthenia gravis (MG) is a T cell-dependent, B cell-mediated disease. The mechanisms for loss of self-tolerance in this disease are not well understood, and recently described regulatory B cell (Breg) subsets have not been thoroughly investigated. B10 cells are a subset of Bregs identified by the production of the immunosuppressive cytokine, interleukin-10 (IL-10). B10 cells are known to strongly inhibit B- and T-cell inflammatory responses in animal models and are implicated in human autoimmunity. In this study, we examined quantitative and qualitative aspects of B10 cells in acetylcholine receptor autoantibody positive MG (AChR-MG) patients and healthy controls. We observed reduced B10 cell frequencies in AChR-MG patients, which inversely correlated with disease severity. Disease severity also affected the function of B10 cells, as B10 cells in the moderate/severe group of MG patients were less effective in suppressing CD4 T-cell proliferation. These results suggest that B10 cell frequencies may be a useful biomarker of disease severity, and therapeutics designed to restore B10 cell frequencies could hold promise as a treatment for this disease through restoration of self-tolerance.

Local Induction of B Cell Interleukin-10 Competency Alleviates Inflammation and Bone Loss in Ligature-Induced Experimental Periodontitis in Mice

Interleukin-10 (IL-10)-producing B cells (B10 cells) play a critical role in the immune system balance by negatively regulating inflammatory responses. This study was conducted to determine the effect of local B10 cell induction on periodontal inflammation and bone loss in ligature-induced experimental periodontitis in vivo Purified spleen B cells from C57BL/6J mice (8 to 10 weeks old) were cultured with CD40 ligand (CD40L) and the Toll-like receptor 9 (TLR9) agonist cytidine-phosphate-guanosine oligodeoxynucleotide (CpG) to determine effective IL-10 induction in vitro Silk ligatures (size 7-0) were tied around the mouse maxillary second molars on day 0, followed by the injection of CD40L and CpG into the palatal gingiva on days 3, 6, and 9. All the mice were sacrificed, and samples were collected on day 14. CD40L and CpG significantly increased the level of IL-10 production by B cells in vitro, although the frequencies of CD1d^hi CD5⁺ and IL-10-producing (IL-10⁺) CD45⁺ cells were decreased. IL-10 was predominantly produced by the CD1d^hi CD5⁺ subpopulation of B cells. In vivo, both IL-10 mRNA expression and the number of IL-10⁺ CD45⁺ cells were significantly increased after gingival injection of CD40L and CpG. Periodontal bone loss was significantly decreased and the gingival expression of IL-1β, tumor necrosis factor alpha, and RANKL was significantly reduced. The number of multinucleated tartrate-resistant acid phosphatase-positive cells along the alveolar bone surface was significantly decreased after gingival injection of CD40L and CpG. This study indicates for the first time that the local induction of B10 cell activity could inhibit periodontal inflammation and bone loss.

The role of regulatory B cells in digestive system diseases

INTRODUCTION

The past decade has provided striking insights into a newly identified subset of B cells known as regulatory B cells (Bregs). In addition to producing antibody, Bregs also regulate diseases via cytokine production and antigen presentation. This subset of B cells has protective and potentially therapeutic effects. However, the particularity of Bregs has caused some difficulties in conducting research on their roles. Notably, human B10 cells, which are Bregs that produce interleukin 10, share phenotypic characteristics with other previously defined B cell subsets, and currently, there is no known surface phenotype that is unique to B10 cells.

METHODS

An online search was performed in the PubMed and Web of Science databases for articles published providing evidences on the role of regulatory B cells in digestive system diseases.

RESULTS AND CONCLUSIONS

Abundant evidence has demonstrated that Bregs play a regulatory role in inflammatory, autoimmune, and tumor diseases, and regulatory B cells play different roles in different diseases, but future work needs to determine the mechanisms by which Bregs are activated and how these cells affect their target cells.

Semaphorin 4C Protects against Allergic Inflammation: Requirement of Regulatory CD138+ Plasma Cells

The regulatory properties of B cells have been studied in autoimmune diseases; however, their role in allergic diseases is poorly understood. We demonstrate that Semaphorin 4C (Sema4C), an axonal guidance molecule, plays a crucial role in B cell regulatory function. Mice deficient in Sema4C exhibited increased airway inflammation after allergen exposure, with massive eosinophilic lung infiltrates and increased Th2 cytokines. This phenotype was reproduced by mixed bone marrow chimeric mice with Sema4C deficient only in B cells, indicating that B lymphocytes were the key cells affected by the absence of Sema4C expression in allergic inflammation. We determined that Sema4C-deficient CD19⁺CD138⁺ cells exhibited decreased IL-10 and increased IL-4 expression in vivo and in vitro. Adoptive transfer of Sema4c^-/- CD19⁺CD138⁺ cells induced marked pulmonary inflammation, eosinophilia, and increased bronchoalveolar lavage fluid IL-4 and IL-5, whereas adoptive transfer of wild-type CD19⁺CD138⁺IL-10⁺ cells dramatically decreased allergic airway inflammation in wild-type and Sema4c^-/- mice. This study identifies a novel pathway by which Th2-mediated immune responses are regulated. It highlights the importance of plasma cells as regulatory cells in allergic inflammation and suggests that CD138⁺ B cells contribute to cytokine balance and are important for maintenance of immune homeostasis in allergic airways disease. Furthermore, we demonstrate that Sema4C is critical for optimal regulatory cytokine production in CD138⁺ B cells.

Estrogen receptor alpha promotes lupus in (NZB×NZW)F1 mice in a B cell intrinsic manner

Lupus is a systemic autoimmune disease characterized by the production of autoreactive antibodies against nuclear antigens. Women are disproportionately affected by lupus, and this sex bias is thought to be due, in large part, to the ability of estrogens to promote lupus pathogenesis. Previously, we have shown that global deletion of estrogen receptor alpha (ERα) significantly attenuated loss of tolerance, immune cell activation, autoantibody production, and the development of lupus nephritis. Here we show that targeted deletion of ERα specifically in B cells retards production of pathogenic autoantibodies and the development of nephritis in lupus-prone (NZB×NZW)F1 mice. Furthermore, we observed that ERα deletion in B cells was associated with decreased B cell activation in young, pre-autoimmune (NZB×NZW)F1 females. Altogether, these data suggest that ERα acts in a B cell-intrinsic manner to control B cell activation, autoantibody production, and lupus nephritis.

CD19+CD24hiCD38hiBregs involved in downregulate helper T cells and upregulate regulatory T cells in gastric cancer

Regulatory B cells (Bregs) play a critical role in inflammation and autoimmune disease. We characterized the role of Bregs in the progression of gastric cancer. We detected an increase in Bregs producing IL-10 both in peripheral blood mononuclear cells (PBMCs) and in gastric tumors. Multicolor flow cytometry analysis revealed that a subset of CD19⁺CD24^hiCD38^hi B cells produces IL-10. Functional studies indicated that increased Bregs do not inhibit the proliferation of CD3⁺T cells or CD4⁺ helper T cells (Th cells). However, Bregs do suppress the secretion of IFN-γ and TNF-α by CD4⁺Th cells. CD19⁺CD24^hiCD38^hiBregs were also found to correlate positively with CD4⁺FoxP3⁺ regulatory T cells (Tregs). Neutralization experiments showed that Bregs convert CD4⁺CD25⁻ effector T cells to CD4⁺FoxP3⁺Tregs via TGF-β1. Collectively, these findings demonstrate that increased Bregs play a immunosuppressive role in gastric cancer by inhibiting T cells cytokines as well as conversion to Tregs. These results may provide new clues about the underlying mechanisms of immune escape in gastric cancer.

Human umbilical cord-derived mesenchymal stem cells protect against experimental colitis via CD5(+) B regulatory cells

Background

To clarify the effect of human umbilical cord-derived mesenchymal stem cell (hUC-MSCs) treatment on colitis and to explore the role of CD5⁺ B cells in MSC therapy.

Methods

The trinitrobenzenesulfonic acid (TNBS)-induced colitis mouse model was used. HUC-MSCs were transferred peritoneally. Survival rates, colitis symptoms, and macroscopic and histologic scores were evaluated. CD4⁺ T helper (Th) cell subgroups and CD5⁺ regulatory B cell (Bregs) in lymphocytes were quantitated by flow cytometry. Cytokine levels were detected by ELISA and Bio-plex. CD5⁺ B cells were isolated for in vitro co-culture and adaptive transfer.

Results

HUC-MSC treatment alleviated TNBS-induced colitis by increasing survival rates, relieving symptoms, and improving macroscopic and histologic scores. Labeled hUC-MSCs were located in the inflamed areas of colitis mice. Increases in regulatory T cells (Tregs) and CD5⁺ B cells and decreases in Th1 cells, Th17 cells, and several pro-inflammatory cytokines were observed with hUC-MSC treatment. After adaptive transfer, CD5⁺ B cells, which were located mainly in the peritoneal lavage fluid, improved TNBS-induced colitis by correcting Treg/Th1/Th17 imbalances. CD5⁺ B cells also inhibited T-cell proliferation and produced interleukin (IL)-10.

Conclusions

HUC-MSCs protected against experimental colitis by boosting the numbers of CD5⁺ B cells and IL-10-producing CD5⁺ Bregs, and correcting Treg/Th17/Th1 imbalances.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0376-2) contains supplementary material, which is available to authorized users.

B in TB: B Cells as Mediators of Clinically Relevant Immune Responses in Tuberculosis

The protective role of B cells and humoral immune responses in tuberculosis infection has been regarded as inferior to cellular immunity directed to the intracellular pathogen Mycobacterium tuberculosis. However, B-cell–mediated immune responses in tuberculosis have recently been revisited in the context of B-cell physiology and antigen presentation. We discuss in this review the diverse functions of B cells in tuberculosis, with a focus on their biological and clinical relevance to progression of active disease. We also present the peptide microarray platform as a promising strategy to discover unknown antigenic targets of M. tuberculosis that could contribute to the better understanding of epitope focus of the humoral immune system against M. tuberculosis.

Enlarged colitogenic T cell population paradoxically supports colitis prevention through the B-lymphocyte-dependent peripheral generation of CD4(+)Foxp3(+) Treg cells

Intestinal inflammation can be induced by the reconstitution of T/B cell-deficient mice with low numbers of CD4⁺ T lymphocytes depleted of CD25⁺Foxp3⁺ regulatory T cells (Treg). Using RAG-knockout mice as recipients of either splenocytes exclusively depleted of CD25⁺ cells or FACS-purified CD4⁺CD25⁻Foxp3⁻ T cells, we found that the augmentation of potentially colitogenic naïve T cell numbers in the inoculum was unexpectedly beneficial for the suppression of colon disease and maintenance of immune homeostasis. Protection against T cell-mediated colitis correlated with a significant increment in the frequency of peripherally-induced CD4⁺CD25⁺Foxp3⁺ T (pTreg) cells, especially in the mesenteric lymph nodes, an effect that required the presence of B cells and CD4⁺CD25⁻Foxp3⁺ cells in physiological proportions. Our findings support a model whereby the interplay between B lymphocytes and a diversified naïve T cell repertoire is critical for the generation of CD4⁺CD25⁺Foxp3⁺ pTreg cells and colitis suppression.

IL-10 Production Is Critical for Sustaining the Expansion of CD5+ B and NKT Cells and Restraining Autoantibody Production in Congenic Lupus-Prone Mice

The development and progression of systemic lupus erythematosus is mediated by the complex interaction of genetic and environmental factors. To decipher the genetics that contribute to pathogenesis and the production of pathogenic autoantibodies, our lab has focused on the generation of congenic lupus-prone mice derived from the New Zealand Black (NZB) strain. Previous work has shown that an NZB-derived chromosome 4 interval spanning 32 to 151 Mb led to expansion of CD5⁺ B and Natural Killer T (NKT) cells, and could suppress autoimmunity when crossed with a lupus-prone mouse strain. Subsequently, it was shown that CD5⁺ B cells but not NKT cells derived from these mice could suppress the development of pro-inflammatory T cells. In this paper, we aimed to further resolve the genetics that leads to expansion of these two innate-like populations through the creation of additional sub-congenic mice and to characterize the role of IL-10 in the suppression of autoimmunity through the generation of IL-10 knockout mice. We show that expansion of CD5⁺ B cells and NKT cells localizes to a chromosome 4 interval spanning 91 to 123 Mb, which is distinct from the region that mediates the majority of the suppressive phenotype. We also demonstrate that IL-10 is critical to restraining autoantibody production and surprisingly plays a vital role in supporting the expansion of innate-like populations.

Decreased IL-10(+) regulatory B cells (Bregs) in lupus nephritis patients

OBJECTIVES

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by B cell-dependent autoantibody production. Recently, a new B-cell subset was discovered that has a regulatory capacity. The aim of this study was to analyse regulatory B cells (Bregs) in SLE patients.

METHOD

Peripheral mononuclear blood cells (PBMCs) of 34 SLE patients fulfilling the American College of Rheumatology (ACR) criteria for SLE and 21 healthy controls (HC) were included. PBMCs were stained for CD19, CD24, and CD38 and analysed by flow cytometry. In vitro stimulated PBMCs with CpG and restimulated with phorbol 12-myristate 13-acetate (PMA) and ionomycin were investigated for IL-10(+) Bregs .

RESULTS

The percentages of circulating CD19(+)CD24(hi)CD38(hi) cells in HC were not different those in from SLE patients. The percentages of IL-10(+) Bregs were significantly decreased in SLE patients, in particular those with lupus nephritis (LN), compared to HC. The proportion was independent of disease activity.

CONCLUSIONS

This is the first study to demonstrate a decrease in IL-10-producing B cells in LN patients compared to HC, reflecting an impaired regulatory function.

Pre-existing CD19-independent GL7(-) Breg cells are expanded during inflammation and in mice with lupus-like disease

Interleukin 10 (IL-10)-producing regulatory B-cells (Bregs) suppress inflammatory responses that mediate autoimmune diseases. However, it is unknown whether Bregs derive from a pre-existing dedicated B-cell lineage or if any B-cell can differentiate into Bregs in response to BCR or TLR activation. GL7(+) B-cells are antigen-experienced differentiated B-cells while GL7(-/lo) are at an early stage of B-cell differentiation. While both GL7(-/lo) and GL7(+) B cells can produce IL-10, differentiation of GL7(-) B-cells into Bregs does not require CD19- or Bcl6-induced signals, suggesting that BCR-induced proliferation or Ig class-switching is not necessary for generation of Breg cells. Of particular importance, we show that GL7(-) Breg cells are dramatically expanded in lupus-like mice and GL7(-) Bregs suppressed inflammatory responses in lupus-like mice by inducing expansion of Foxp3(+)Treg cells. Taken together, these results suggest that pre-existing GL7(-)IL-10(+) cells are expanded during inflammation, differentiate into GL7(+) Bregs and contribute to immune-regulation in lupus-like mice.

Mammary-tumor-educated B cells acquire LAP/TGF-β and PD-L1 expression and suppress anti-tumor immune responses

B lymphocytes play a role in inhibiting the immune response against certain tumors, but the underlying mechanisms are poorly understood. EMT-6 mammary tumors grow well in wild-type (WT) mice but show reduced growth in B-cell-deficient μ(-/-) BALB/c mice (BCDM). WT mice demonstrate extensive B-cell infiltration into the tumor bed, reduced CD8(+) T cell and CD49(+) NK cell infiltration, and markedly reduced cytolytic T-cell response relative to BCDM. Expression of LAP/TGF-β1, CD80, CD86 and PD-L1 is significantly increased in tumor-infiltrating B cells (TIL-B) relative to splenic B cells. LAP/TGF-β1 expression on TIL-B progressively increased from 5.4±1.7% on day 8 to 43.1±6.1% by day 21 post tumor implantation. Co-culture of EMT-6 tumor cells with Naive-B cells ex vivo generated B cells (EMT6-B) with a similar immunophenotype to TIL-B. Purified TIL-B, or in-vitro-generated EMT6-B suppressed CD4(+), CD8(+) and CD4(+)CD25(-) T-cell proliferation, and Th1 cytokine secretion, and also suppressed purified NK-cell proliferation in response to IL-15, compared to naive splenic B cells. Acquired B regulatory function required direct tumor cell: B-cell contact, and was partially reversed by antibody to TGF-β or PD-L1, leading to tumor rejection in vivo B-cell acquisition of a suppressive phenotype following tumor infiltration may result in profound inhibition of T-cell anti-tumor responses.

IL-10-produced by human transitional B-cells down-regulates CD86 expression on B-cells leading to inhibition of CD4+T-cell responses

A novel subset of human regulatory B-cells has recently been described. They arise from within the transitional B-cell subpopulation and are characterised by the production of IL-10. They appear to be of significant importance in regulating T-cell immunity in vivo. Despite this important function, the molecular mechanisms by which they control T-cell activation are incompletely defined. Here we show that transitional B-cells produced more IL-10 and expressed higher levels of IL-10 receptor after CD40 engagement compared to other B-cell subsets. Furthermore, under this stimulatory condition, CD86 expressed by transitional B-cells was down regulated and T-cell proliferation was reduced. We provide evidence to demonstrate that the down-regulation of CD86 expression by transitional B-cells was due to the autocrine effect of IL-10, which in turn leads to decreased T-cell proliferation and TNF-α production. This analysis was further extended to peripheral B-cells in kidney transplant recipients. We observed that B-cells from patients tolerant to the graft maintained higher IL-10 production after CD40 ligation, which correlates with lower CD86 expression compared to patients with chronic rejection. Hence, the results obtained in this study shed light on a new alternative mechanism by which transitional B-cells inhibit T-cell proliferation and cytokine production.

Mesenteric IL-10-producing CD5+ regulatory B cells suppress cow's milk casein-induced allergic responses in mice

Food allergy is a hypersensitive immune reaction to food proteins. We have previously demonstrated the presence of IL-10-producing CD5(+) B cells and suggested their potential role in regulating cow's milk casein allergy in humans and IgE-mediated anaphylaxis in mice. In this study, we determined whether IL-10-producing CD5(+) regulatory B cells control casein-induced food allergic responses in mice and, if so, the underlying mechanisms. The induction of oral tolerance (OT) by casein suppressed casein-induced allergic responses including the decrease of body temperature, symptom score, diarrhea, recruitment of mast cells and eosinophils into jejunum, and other biological parameters in mice. Notably, the population of IL-10-producing CD5(+) B cells was increased in mesenteric lymph node (MLN), but not in spleen or peritoneal cavity (PeC) in OT mice. The adoptive transfer of CD5(+) B cells from MLN, but not those from spleen and PeC, suppressed the casein-induced allergic responses in an allergen-specific and IL-10-dependent manner. The inhibitory effect of IL-10-producing CD5(+) B cells on casein-induced allergic response was dependent on Foxp3(+) regulatory T cells. Taken together, mesenteric IL-10-producing regulatory B cells control food allergy via Foxp3(+) regulatory T cells and could potentially act as a therapeutic regulator for food allergy.

Advances in understanding pathogenesis of primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by chronic and progressive cholestasis. In recent years, the incidence and prevalence of PBC are increasing year by year. However, the etiology and pathogenesis are not fully understood. It is believed that genetic susceptibility, environmental factors, and immunologic tolerance are related with the pathogenesis of PBC. This article reviews the progress in the understanding of the pathogenesis of PBC.

Therapeutic utility of the newly discovered properties of interleukin-21

Since its discovery in 2000, interleukin-21 (IL-21) has been shown to display a broad spectrum of pleiotropic actions including the regulation of development, differentiation and function of lymphoid-myeloid cells. More specifically, IL-21 modulates the effector functions of T, B and NK cells, which not only have key roles in antitumoral and antiviral immunity but also in exerting major effects on inflammatory responses promoting the development of autoimmune diseases. Recent studies have unveiled an unexpected role for IL-21 in immune regulation and de novo T-cell development. While highlighting its critical role in immunity, this review will mainly focus on recent advances in IL-21 biology and how such newly discovered properties could potentially be exploited therapeutically in the establishment of future clinical trials.

Treatment of dextran sodium sulfate-induced experimental colitis by adoptive transfer of peritoneal cells

The adoptive transfer of the natural regulatory B cells and macrophages should be a useful treatment for inflammation and autoimmune disease. However, it is usually difficult to isolate these cells from the tissues and expand them. Here, we investigated the feasibility of adoptively transferring peritoneal cells (PCs) as a treatment for DSS-induced colitis. We found that peritoneal cavity can provide an easily accessible site for harvesting enough number of PCs, namely, two-dose PCs for the treatment from a mouse in one operation. Adoptive therapy of these cells from healthy mice or those with disease is effectively in reducing the disease activity score. The natural B cells and macrophages of the infused PCs can selectively migrate to lesion sites and regulate the expression of Stat3, NF−κB, Smad3 and Smad7. Additionally, PCs exert dual activity of IL-10 and TGF-β secreted spontaneously by both peritoneal B cells and macrophages, which in turn enhance the induction of regulatory B cells and Macrophages in microenvironment of inflammation. Moreover, PCs can re-establish immunological tolerance in the OVA-immunized mice. Thus, our findings provide a new strategy for colitis therapy and could be of importance in additional exploration of other inflammation and autoimmune diseases therapy.

RETRACTED: Aberrant frequency of IL-10-producing B cells and its association with Treg and MDSC cells in Non Small Cell Lung Carcinoma patients

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). The Editor-in-Chief has retracted this article due to serious problems with copied and re-labeled images in several figures. Specifically, the problematic items are the HC and Stage I samples in figure 1D (IL-10/CD19) and figure 2B (CD127/CD25), in which the flow dot plots outside of the boxes are identical. This strongly suggests that the data was manipulated. The authors were unable to provide the raw data files to prove otherwise. This makes the overall conclusions of the paper unreliable and violates our ethical publishing policies. The corresponding author, Liannv Qiu takes full responsibility and apologizes to all co-authors in this article, and the editors and readership of Human Immunology for any negative impact this may have on the journal.

IL-10-independent regulatory B-cell subsets and mechanisms of action

Although classically B cells are known to play important roles in immune protection via humoral immunity, recently their regulatory mechanisms have been best appreciated in the context of autoimmunity. Several studies have identified different subsets of regulatory B cells that vary not only in their phenotype but also in their mechanism of action. Although the best-studied mechanism of B-cell immune regulation is IL-10 production, other IL-10-independent mechanisms have been proposed. These include maintenance of CD4(+)Foxp3(+) regulatory T cells; production of transforming growth factor-β, IL-35, IgM or adenosine or expression of PD-L1 (programmed death 1 ligand 1) or FasL (Fas ligand). Given that B-cell-targeted therapy is being increasingly used in the clinic, a complete understanding of the mechanisms whereby B cells regulate inflammation associated with specific diseases is required for designing safe and effective immunotherapies targeting B cells.

The expanding family of regulatory B cells

Over the last decade it has become evident that in addition to producing antibody, B cells activate the immune system by producing cytokines and via antigen presentation. In addition, B cells also exhibit immunosuppressive functions via diverse regulatory mechanisms. This subset of B cells, known as regulatory B cells (Bregs), contributes to the maintenance of tolerance, primarily via the production of IL-10. Studies in experimental animal models, as well as in patients with autoimmune diseases, have identified multiple Breg subsets exhibiting diverse mechanisms of immune suppression. In this review, we describe the different Breg subsets identified in mice and humans, and their diverse mechanisms of suppression in different disease settings.

The regulatory role of B cells in autoimmunity, infections and cancer: Perspectives beyond IL10 production

The term regulatory B cells (B regs) is ascribed to a heterogeneous population of B cells with the function of suppressing inflammatory responses. They have been described mainly during the last decade in the context of different immune-mediated diseases. Most of the work on B regs has been focused on IL-10-producing B cells. However, B cells can exert regulatory functions independently of IL-10 production. Here we discuss the phenotypes, development and effector mechanisms of B regs and advances in their role in autoimmunity, infections and cancer.

Infusion of dendritic cells carrying donor lymphocytes treated with 8-methoxypsoralen and ultraviolet A light induces CD19+ IL-10+ regulatory B cells and promotes skin allograft survival

PUVA-SP DCs are immature dendritic cells (imDCs) that have taken up donor splenic lymphocytes treated with 8-methoxypsoralen and ultraviolet A light (PUVA-SPs). Phagocytosis of donor PUVA-SPs does not stimulate phenotype maturation of recipient imDCs, and infusion of PUVA-SP DCs can induce CD4(+)CD25(high)Foxp3(+) regulatory T cells (Treg). However, the regulatory effect of PUVA-SP DCs on B cells is poorly understood. In this study, we compared PUVA-SP DCs with imDCs in terms of lipopolysaccharide (LPS) responsiveness and flow cytometric analysis of interleukin (IL) 10 expression in splenic CD19(+)B cells. Our results demonstrate that PUVA-SP DCs can suppress subsequent LPS-induced DC maturation and that infusion of PUVA-SP DCs, in the absence of an immunosuppressant, significantly promotes skin allograft survival. This effect was associated with up-regulation of circulating regulatory B cells exhibiting preferential IL-10 secretion. Our results suggest that effective treatments involving infusion of PUVA-SP DCs is likely related to the modulation not only of T-cell and Treg functions but also of B-cell and regulatory B-cell (Breg) functions.

Regulatory B cells mediate tolerance to apoptotic self in health: implications for disease

B cells are able to regulate immune responses through the secretion of IL-10 and other inhibitory cytokines, though no transcription factor that can define 'regulatory B cells' as a separate lineage has yet been found. Instead it is likely that this function arises as a result of the immune context in which B cells find themselves and the stimuli they perceive. However, some B cells found within the B1a and the marginal zone subsets have a greater propensity to produce IL-10 than others. What are the natural stimuli for these cells to induce immune regulation? We discuss the role that the recognition of autoantigens exposed by apoptotic cells plays in stimulating IL-10 production in mouse and human studies. This mechanism involves the recognition and uptake of self-antigens by autoreactive BCRs, for delivery to endocytic compartments, where apoptosis-derived DNA binds to TLR9, driving IL-10 production. These 'natural' regulatory B cells represent a way of maintaining tolerance to self. We discuss how this may operate in inflammatory lesions where there is an excess of apoptotic leukocytes and how this impacts on our understanding of autoimmune disease.

Regulatory B10 cell development and function

B cells are known to instigate and promulgate immune responses by producing antibodies and presenting antigens to T cells. However, a rare but potent B-cell subset in both humans and mice is capable of inhibiting immune responses through the production of the anti-inflammatory cytokine IL-10. Regulatory B cells do not express any unique combination of surface markers but instead represent a small population of B cells that have acquired the unique ability to produce IL-10. This numerically rare B-cell subset is therefore functionally referred to as 'B10 cells' to reflect both their molecular program and the fact that their anti-inflammatory effects in models of autoimmunity, infection and cancer are solely attributable to IL-10 production. As with most B cells, B10 cell development and function appear to be predominantly, if not exclusively, driven by antigen-receptor signals. Once generated, B10 cells respond to both innate and adaptive immune signals, with a requirement for antigen-specific local interactions with T cells to induce IL-10 production and to provide optimal immune suppression in mouse models of autoimmune disease. B10 cells therefore provide an antigen-specific mechanism for delivering IL-10 locally to sites of immune activation and inflammation. The ability of B10 cells to regulate innate and adaptive immune responses makes them an ideal therapeutic target for the treatment of many immune-related disorders.

Impaired Function of CD5+CD19+CD1dhi B10 Cells on IgE Secretion in an Atopic Dermatitis-Like Mouse Model

Atopic dermatitis (AD) is a chronic inflammatory pruritic skin disease in which the pathogenic mechanism is complicated and not completely understood. Reports on the role of regulated cells in AD have recently evolved to regulate B cells, which may play a role in allergic inflammation as well. In the present study, we examined the frequency and regulatory function of CD5⁺CD19⁺CD1d^hi B10 cells in an AD-like mouse model. Our results showed that the percentage of CD5⁺CD19⁺CD1d^hi B10 cells increased while the frequency of IL-10-producing B cells in CD19⁺B cells decreased in the mice of AD group. Moreover, no difference in the percentage of B10pro+B10 cells was observed between the AD and control groups. Strikingly, B10 cells from control mice effectively inhibited IgE secretion, whereas the suppressive function of B10 cells from the AD mice was significantly decreased, which was similar to that observed in the group without B10. Altogether, these results suggest that the number of IL-10-producing B cells decreased in the AD group and these cells showed a defective regulatory function on IgE secretion.

Increased circulating interleukin 10-secreting B cells in patients with dilated cardiomyopathy

OBJECTIVES

Regulatory B cells (Bregs) have recently been implicated in the pathogenesis of autoimmune diseases. However, their role in the pathogenesis of dilated cardiomyopathy (DCM) remains uncertain. We examined the levels of circulating interleukin 10 (IL-10)-secreting Bregs in patients with DCM.

METHODS

The frequency of CD19+IL-10+-, CD19+CD5+-, CD19+CD5+CD1d+-, and CD19+CD5+CD1d+IL-10+-B cells in peripheral blood from DCM patients, heart failure (HF) control patients, and healthy controls (HCs) were analyzed by flow cytometry.

RESULTS

DCM and HF control patients showed significantly elevated heart rate, increased left ventricular end-diastolic and left ventricular end-systolic diameters, higher levels of serum brain natriuretic peptide and reduced left ventricular ejection fraction, compared to subjects in the HC group. DCM patients showed significantly elevated levels of circulating CD19+IL-10+-, CD19+CD5+-, CD19+CD5+CD1d+-, and CD19+CD5+CD1d+IL-10+-B cells than HF control and HC patients (all P < 0.05).

CONCLUSIONS

DCM patients exhibited elevated peripheral blood IL-10-secreting B cell levels, suggesting that IL-10-secreting B cells may play an important role in the pathogenesis of DCM.

Suppression of autoimmunity by CD5(+) IL-10-producing B cells in lupus-prone mice

Systemic lupus erythematosus is a complex autoimmune disorder characterized by the production of pathogenic anti-nuclear antibodies. Previous work from our laboratory has shown that the introgression of a New Zealand Black-derived chromosome 4 interval onto a lupus-prone background suppresses the disease. Interestingly, the same genetic interval promoted the expansion of both Natural Killer T- and CD5(+) B cells in suppressed mice. In this study, we show that ablation of NKT cells with a CD1d knockout had no impact on either the suppression of lupus or the expansion of CD5(+) B cells. On the other hand, suppressed mice had an expanded population of IL-10-producing B cells that predominantly localized to the CD5(+)CD1d(low) compartment. The expansion of CD5(+) B cells negatively correlated with the frequency of pro-inflammatory IL-17 A-producing T-cells and kidney damage. Adoptive transfer with a single injection of total B cells with an enriched CD5(+) compartment reduced the frequency of memory/activated, IFNγ-producing, and IL-17 A-producing CD4 T-cells but did not significantly reduce autoantibody levels. Taken together, these data suggest that the expansion of CD5(+) IL-10-producing B cells and not NKT cells protects against lupus in these mice, by limiting the expansion of pro-inflammatory IL-17 A- and IFNγ-producing CD4 T-cells.

Regulatory B cells in human inflammatory and autoimmune diseases: from mouse models to clinical research

B cells have been generally considered to be positive regulators of immune responses because of their ability to produce antigen-specific antibodies and to activate T cells through antigen presentation. Impairment of B cell development and function may cause inflammatory and autoimmune diseases. Recently, specific B cell subsets that can negatively regulate immune responses have been described in mouse models of a wide variety of inflammatory and autoimmune diseases. The concept of those B cells, termed regulatory B cells, is now recognized as important in the murine immune system. Among several regulatory B cell subsets, IL-10-producing regulatory B cells are the most widely investigated. On the basis of discoveries from studies of such mice, human regulatory B cells that produce IL-10 in most cases are becoming an active area of research. There have been emerging data suggesting the importance of human regulatory B cells in various diseases. Revealing the immune regulation mechanisms of human regulatory B cells in human inflammatory and autoimmune diseases could lead to the development of novel B cell targeted therapies. This review highlights the current knowledge on regulatory B cells, mainly IL-10-producing regulatory B cells, in animal models of inflammatory and autoimmune diseases and in clinical research using human samples.

B10 cells: a functionally defined regulatory B cell subset

B cells are commonly thought to enhance inflammatory immune responses. However, specific regulatory B cell subsets recently were identified that downregulate adaptive and innate immunity, inflammation, and autoimmunity through diverse molecular mechanisms. In both mice and humans, a rare, but specific, subset of regulatory B cells is functionally characterized by its capacity to produce IL-10, a potent inhibitory cytokine. For clarity, this regulatory B cell subset has been labeled as B10 cells, because their ability to downregulate immune responses and inflammatory disease is fully attributable to IL-10, and their absence or loss exacerbates disease symptoms in mouse models. This review preferentially focuses on what is known about mouse B10 cell development, phenotype, and effector function, as well as on mechanistic studies that demonstrated their functional importance during inflammation, autoimmune disease, and immune responses.

Killer B lymphocytes and their fas ligand positive exosomes as inducers of immune tolerance

Induction of immune tolerance is a key process by which the immune system is educated to modulate reactions against benign stimuli such as self-antigens and commensal microbes. Understanding and harnessing the natural mechanisms of immune tolerance may become an increasingly useful strategy for treating many types of allergic and autoimmune diseases, as well as for improving the acceptance of solid organ transplants. Our laboratory and others have been interested in the natural ability of some B lymphocytes to express the death-inducing molecule Fas ligand (FasL), and their ability to kill T helper (T_H) lymphocytes. We have recently shown that experimental transformation of human B cells by a non-replicative variant of Epstein-Barr virus (EBV) consistently resulted in high expression of functional FasL protein. The production and release of FasL⁺ exosomes that co-expressed major histocompatibility complex (MHC) class II molecules and had the capacity to kill antigen-specific T_H cells was also observed. Several lines of evidence indicate that FasL+ B cells and FasL⁺MHCII⁺ exosomes have important roles in natural immune tolerance and have a great deal of therapeutic potential. Taken together, these findings suggest that EBV-immortalized human B lymphoblastoid cell lines could be used as cellular factories for FasL⁺ exosomes, which would be employed to therapeutically establish and/or regain immune tolerance toward specific antigens. The goals of this review are to summarize current knowledge of the roles of FasL⁺ B cells and exosomes in immune regulation, and to suggest methods of manipulating killer B cells and FasL⁺ exosomes for clinical purposes.

Regulatory B Cells and Mechanisms

Regulatory B cells have gained prominence in their role as modulators of the immune response against tumors, infectious diseases, and autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis, among others. The concept of regulatory B cells has been strongly associated with interleukin (IL)-10 production; however, there is growing evidence that supports the existence of other regulatory mechanisms, such as the production of transforming growth factor β (TGF-β), induced cell death of effector T cells, and the induction of CD4(+)CD25(-)Foxp3(+) regulatory T cells. The regulatory function of B cells has been associated with the presence and activation of molecules such as CD40, CD19, CD1d, and BCR. Alterations in signaling by any of these pathways leads to a marked defect in regulatory B cells and to increased clinical symptoms and proinflammatory signs, both in murine models and in autoimmune diseases in humans. B cells mainly exert their regulatory effect through the inhibition of proliferation and production of proinflammatory mediators, such as TNF-α, IFN-γ, and IL-17 by CD4(+) T cells. A better understanding of how regulatory B cells function will offer new perspectives with regard to the treatment of various human diseases.

IFN-β treatment requires B cells for efficacy in neuroautoimmunity

IFN-β remains the most widely prescribed treatment for relapsing remitting multiple sclerosis. Despite widespread use of IFN-β, the therapeutic mechanism is still partially understood. Particularly, the clinical relevance of increased B cell activity during IFN-β treatment is unclear. In this article, we show that IFN-β pushes some B cells into a transitional, regulatory population that is a critical mechanism for therapy. IFN-β treatment increases the absolute number of regulatory CD19(+)CD24(++)CD38(++) transitional B cells in peripheral blood relative to treatment-naive and Copaxone-treated patients. In addition, we found that transitional B cells from both healthy controls and IFN-β-treated MS patients are potent producers of IL-10, and that the capability of IFN-β to induce IL-10 is amplified when B cells are stimulated. Similar changes are seen in mice with experimental autoimmune encephalomyelitis. IFN-β treatment increases transitional and regulatory B cell populations, as well as IL-10 secretion in the spleen. Furthermore, we found that IFN-β increases autoantibody production, implicating humoral immune activation in B cell regulatory responses. Finally, we demonstrate that IFN-β therapy requires immune-regulatory B cells by showing that B cell-deficient mice do not benefit clinically or histopathologically from IFN-β treatment. These results have significant implications for the diagnosis and treatment of relapsing remitting multiple sclerosis.

Characterization of B cells in muscle-specific kinase antibody myasthenia gravis

OBJECTIVE

To characterize B-cell subsets in patients with muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG).

METHODS

In accordance with Human Immunology Project Consortium guidelines, we performed polychromatic flow cytometry and ELISA assays in peripheral blood samples from 18 patients with MuSK MG and 9 healthy controls. To complement a B-cell phenotype assay that evaluated maturational subsets, we measured B10 cell percentages, plasma B cell-activating factor (BAFF) levels, and MuSK antibody titers. Immunologic variables were compared with healthy controls and clinical outcome measures.

RESULTS

As expected, patients treated with rituximab had high percentages of transitional B cells and plasmablasts and thus were excluded from subsequent analysis. The remaining patients with MuSK MG and controls had similar percentages of total B cells and naïve, memory, isotype-switched, plasmablast, and transitional B-cell subsets. However, patients with MuSK MG had higher BAFF levels and lower percentages of B10 cells. In addition, we observed an increase in MuSK antibody levels with more severe disease.

CONCLUSIONS

We found prominent B-cell pathology in the distinct form of MG with MuSK autoantibodies. Increased BAFF levels have been described in other autoimmune diseases, including acetylcholine receptor antibody-positive MG. This finding suggests a role for BAFF in the survival of B cells in MuSK MG, which has important therapeutic implications. B10 cells, a recently described rare regulatory B-cell subset that potently blocks Th1 and Th17 responses, were reduced, which suggests a potential mechanism for the breakdown in immune tolerance in patients with MuSK MG.

Interleukin-10+ regulatory B cells arise within antigen-experienced CD40+ B cells to maintain tolerance to islet autoantigens

Impaired regulatory B cell (Breg) responses are associated with several autoimmune diseases in humans; however, the role of Bregs in type 1 diabetes (T1D) remains unclear. We hypothesized that naturally occurring, interleukin-10 (IL-10)-producing Bregs maintain tolerance to islet autoantigens, and that hyperglycemic nonobese diabetic (NOD) mice and T1D patients lack these potent negative regulators. IgVH transcriptome analysis revealed that islet-infiltrating B cells in long-term normoglycemic (Lnglc) NOD, which are naturally protected from diabetes, are more antigen-experienced and possess more diverse B-cell receptor repertoires compared to those of hyperglycemic (Hglc) mice. Importantly, increased levels of Breg-promoting CD40(+) B cells and IL-10-producing B cells were found within islets of Lnglc compared to Hglc NOD. Likewise, healthy individuals showed increased frequencies of both CD40(+) and IL-10(+) B cells compared to T1D patients. Rituximab-mediated B-cell depletion followed by adoptive transfer of B cells from Hglc mice induced hyperglycemia in Lnglc human CD20 transgenic NOD mouse models. Importantly, both murine and human IL-10(+) B cells significantly abrogated T-cell-mediated responses to self- or islet-specific peptides ex vivo. Together, our data suggest that antigen-matured Bregs may maintain tolerance to islet autoantigens by selectively suppressing autoreactive T-cell responses, and that Hglc mice and individuals with T1D lack this population of Bregs.

B Cells with Regulatory Function in Animal Models of Autoimmune and Non-Autoimmune Diseases

Although the identification of B cell subsets with negative regulatory functions and the definition of their mechanisms of action are recent events, the important negative regulatory roles of B cells in immune responses are now broadly recognized. There is an emerging appreciation for the pivotal role played by B cells in several areas of human diseases including autoimmune diseases and non-autoimmune diseases such as parasite infections and cancer. The recent research advancement of regulatory B cells in human disease coincides with the vastly accelerated pace of research on the bridging of innate and adaptive immune system. Current study and our continued research may provide better understanding of the mechanisms that promote regulatory B10 cell function to counteract exaggerated immune activation in autoimmune as well as non-autoimmune conditions. This review is focused on the current knowledge of BREG functions studied in animal models of autoimmune and non-autoimmune diseases.