IL-10-producing regulatory B10 cells inhibit intestinal injury in a mouse model. Am J Pathol. 2011;178:735-743. [PMID: 21281806 DOI: 10.1016/j.ajpath.2010.10.022]

The immune potential and immunopathology of cytokine-producing B cell subsets: a comprehensive review

B lymphocytes are generally recognized for their potential to mediate humoral immunity by producing different antibody isotypes and being involved in opsonization and complement fixation. Nevertheless, the non-classical, antibody-independent immune potential of B cell subsets has attracted much attention especially in the past decade. These B cells can release a broad variety of cytokines (such as IL-2, IL-4, IL-6, IL-10, IL-17, IFN-α, IFN-γ, TNF-α, TGF-β, LT), and can be classified into distinct subsets depending on the particular cytokine profile, thus emerging the concept of cytokine-producing B cell subsets. Although there is still controversy surrounding the key cell surface markers, intracellular factors and cellular origins of cytokine-producing B cell subsets, accumulating evidence indicates that these B cells are endowed with great potential to regulate both innate and adaptive arms of immune system though releasing cytokines. On the one hand, they promote immune responses through mounting Th1/Th2/Th17 and neutrophil response, inducing DC maturation and formation of lymphoid structures, increasing NK cell and macrophage activation, enhancing development of themselves and sustaining antibody production. On the other hand, they can negatively regulate immune responses by suppressing Th cell responses, inhibiting Tr1 cell and Foxp3(+) Treg differentiation, impairing APC function and pro-inflammatory cytokine release by monocytes, and inducing CD8(+) T cell anergy and CD4(+) T cell apoptosis. Therefore, cytokine-producing B cell subsets have multifunctional functions in health and diseases, playing pathologic as well as protective roles in autoimmunity, infection, allergy, and even malignancy. In this review, we revisit the history of discovering cytokine-producing B cells, describe the identification of cytokine-producing B cell subsets, introduce the origins of cytokine-producing B cell subsets as well as molecular and cellular mechanisms for their differentiation, and summarize the recent progress made toward understanding the unexpectedly complex and potentially opposing roles of cytokine-producing B cells in immunological disorders.

B-cell receptor signaling inhibitors for treatment of autoimmune inflammatory diseases and B-cell malignancies

B-cell receptor (BCR) signaling is essential for normal B-cell development, selection, survival, proliferation, and differentiation into antibody-secreting cells. Similarly, this pathway plays a key role in the pathogenesis of multiple B-cell malignancies. Genetic and pharmacological approaches have established an important role for the Spleen tyrosine kinase (Syk), Bruton's tyrosine kinase (Btk), and phosphatidylinositol 3-kinase isoform p110delta (PI3Kδ) in coupling the BCR and other BCRs to B-cell survival, migration, and activation. In the past few years, several small-molecule inhibitory drugs that target PI3Kδ, Btk, and Syk have been developed and shown to have efficacy in clinical trials for the treatment of several types of B-cell malignancies. Emerging preclinical data have also shown a critical role of BCR signaling in the activation and function of self-reactive B cells that contribute to autoimmune diseases. Because BCR signaling plays a major role in both B-cell-mediated autoimmune inflammation and B-cell malignancies, inhibition of this pathway may represent a promising new strategy for treating these diseases. This review summarizes recent achievements in the mechanism of action, pharmacological properties, and clinical activity and toxicity of these BCR signaling inhibitors, with a focus on their emerging role in treating lymphoid malignancies and autoimmune disorders.

Role of regulatory B cells in chronic intestinal inflammation: association with pathogenesis of Crohn's disease

The role of regulatory B cells (Bregs) producing interleukin (IL)-10 in the pathogenesis of inflammatory bowel diseases remains unknown. We investigated IL-10 production in B cells from patients with inflammatory bowel diseases and immunoregulatory functions of Bregs in experimental colitis mouse models. CpG DNA-induced IL-10 production in peripheral blood B cells isolated from patients with inflammatory bowel diseases and control subjects was examined. CD19 and CD1d were used for evaluating possible cell surface markers of Bregs. Colitis models of severe combined immunodeficiency mice were established by adoptive transfer of whole CD4 T cells or regulatory T cell (Treg)-depleted T cells (CD4CD25) isolated from SAMP1/Yit mice and the function of Bregs in intestinal inflammation was elucidated by evaluating the effects of cotransfer of whole or Breg-depleted B cells. CpG DNA-induced IL-10 production was significantly decreased in B cells from patients with Crohn's disease (CD), as compared with those from healthy controls, whereas Bregs were found to be enriched in a population of CD19 and CD1d B cells isolated from both human and mouse samples. The severity of intestinal inflammation was significantly increased in the Breg-depleted mice, with similar results also found in adoptive transfer colitis model mice even after Treg depletion. Our findings show that Bregs, characterized by the cell surface markers CD19 and CD1d, significantly reduced experimental colitis regardless of the presence or absence of Tregs. These results suggest that a deficiency or decrease of Bregs function exacerbates intestinal inflammation, which may be associated with the pathogenesis of CD.

Interleukin-10-producing B cells and the regulation of immunity

B cells are usually considered primarily for their unique capacity to produce antibodies after differentiation into plasma cells. In addition to their roles as antibody-producing cells, it has become apparent during the last 10 years that B cells also perform important functions in immunity through the production of cytokines. In particular, it was shown that B cells could negatively regulate immunity through provision of interleukin (IL)-10 during autoimmune and infectious diseases in mice. Here, we review data on the suppressive functions of B cells in mice with particular emphasis on the signals controlling the acquisition of such suppressive functions by B cells, the phenotype of the B cells involved in the negative regulation of immunity, and the processes targeted by this inhibitory circuit. Finally, we discuss the possibility that human B cells might also perform similar inhibitory functions through the provision of IL-10, and review data suggesting that such B cell-mediated regulatory activities might be impaired in patients with autoimmune diseases.

Regulatory B cells in mouse models of intestinal inflammation

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition with increasing incidence and prevalence around the world. Although B cells had generally been believed to play a pathogenic role in IBD due to the production of autoantibodies, a growing body of evidence from mouse models suggests the coexistence of pathogenic B cells and regulatory B cells, termed Breg, in this disorder. Since some unique techniques are required to closely study the Breg in gut-associated lymphoid tissues (GALT), we herein describe how to induce colitis in mice and how to analyze the phenotype and function of GALT-specific Breg.

B-cell-derived IL-10 does not vitally contribute to the clinical course of glomerulonephritis

IL-10-secreting regulatory B cells have been postulated as negative mediators of inflammation. However, their impact on immune-mediated diseases requires further investigation. We recently found that IL-10-secreting B cells infiltrate the kidney during crescentic glomerulonephritis (GN). We therefore studied the function of B-cell-derived IL-10 in light of the potential risks associated with increasingly used B-cell depleting therapies. Lack of IL-10 production by B cells, however, did not influence acute or adaptively mediated progressive renal injury in terms of renal function and histological damage in the nephrotoxic nephritis model of GN. Renal leukocyte infiltration and cytokine expression were similar apart from increased macrophages in mice lacking B-cell-derived IL-10. Systemic immune responses as assessed by cytokine production, leukocyte composition, proliferation, and activation were indistinguishable, while production and renal deposition of Ag-specific IgG were mildly impaired in the absence of B-cell-produced IL-10. Importantly, detailed analysis of systemic and renal regulatory T cells did not show any differences between nephritic mice bearing IL-10-deficient B cells and WT controls. Finally, studies in reporter mice revealed that B cells are only a minor source of systemic IL-10. In summary, our data reveal that endogenous B-cell-derived IL-10 does not play a major role in the nephrotoxic nephritis model of crescentic GN.

Monogenic diseases associated with intestinal inflammation: implications for the understanding of inflammatory bowel disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, has multifactorial aetiology with complex interactions between genetic and environmental factors. Over 150 genetic loci are associated with IBD. The genetic contribution of the majority of those loci towards explained heritability is low. Recent studies have reported an increasing spectrum of human monogenic diseases that can present with IBD-like intestinal inflammation. A substantial proportion of patients with those genetic defects present with very early onset of intestinal inflammation. The 40 monogenic defects with IBD-like pathology selected in this review can be grouped into defects in intestinal epithelial barrier and stress response, immunodeficiencies affecting granulocyte and phagocyte activity, hyper- and autoinflammatory disorders as well as defects with disturbed T and B lymphocyte selection and activation. In addition, there are defects in immune regulation affecting regulatory T cell activity and interleukin (IL)-10 signalling. Related to the variable penetrance of the IBD-like phenotype, there is a likely role for modifier genes and gene-environment interactions. Treatment options in this heterogeneous group of disorders range from anti-inflammatory and immunosuppressive therapy to blockade of tumour necrosis factor α and IL-1β, surgery, haematopoietic stem cell transplantation or gene therapy. Understanding of prototypic monogenic 'orphan' diseases cannot only provide treatment options for the affected patients but also inform on immunological mechanisms and complement the functional understanding of the pathogenesis of IBD.

The value of experimental models of colitis in predicting efficacy of biological therapies for inflammatory bowel diseases

During the last decade, biological therapies have an increasing share in the modern therapeutics of various diseases including inflammatory bowel diseases (IBD). Animal models of IBD have often been used to identify the targets of biological therapies, to test their relevance to disease pathogenesis, to assess their therapeutic efficacy in vivo, and to check for drug toxicity. In the field of inflammatory diseases the majority of biologics under development have failed to reach the clinic. This review examines the ability of preclinical data from animal models of IBD to predict success or failure of biologics in human IBD. Specifically, it describes the murine models of IBD, the mechanism of disease induction, the phenotype of the disease, its relevance to human IBD, and the specific immunological features of disease pathogenesis in each model and mainly compares the results of the phase II and III trials of biologics in IBD with preclinical data obtained from studies in animal models. Finally, it examines the possible reasons for low success in translation from bench to bedside and offers some suggestions to improve translation rates.

Trametes versicolor protein YZP activates regulatory B lymphocytes - gene identification through de novo assembly and function analysis in a murine acute colitis model

Background

Trametes versicolor (Yun-Zhi) is a medicinal fungus used as a chemotherapy co-treatment to enhance anti-tumor immunity. Although the efficacies of T. versicolor extracts have been documented, the active ingredients and mechanisms underlying the actions of these extracts remain uncharacterized.

Results

We purified a new protein, YZP, from the fruiting bodies of T. versicolor and identified the gene encoding YZP using RNA-seq and de novo assembly technologies. YZP is a 12-kDa non-glycosylated protein comprising 139 amino acids, including an 18-amino acids signal peptide. YZP induced a greater than 60-fold increase in IL-10 secretion in mice B lymphocytes; moreover, YZP specifically triggered the differentiation of CD1d⁺ B cells into IL-10-producing regulatory B cells (Bregs) and enhanced the expression of CD1d. YZP-induced B cells suppressed approximately 40% of the LPS-activated macrophage production of inflammatory cytokines in a mixed leukocyte reaction and significantly alleviated the disease activity and colonic inflammation in a DSS-induced acute colitis murine model. Furthermore, YZP activated Breg function via interaction with TLR2 and TLR4 and up-regulation of the TLR-mediated signaling pathway.

Conclusions

We purified a novel Breg-stimulating protein, YZP, from T. versicolor and developed an advanced approach combining RNA-seq and de novo assembly technologies.to clone its gene. We demonstrated that YZP activated CD1d⁺ Breg differentiation through TLR2/4-mediated signaling pathway, and the YZP-stimulated B cells exhibited anti-inflammatory efficacies in vitro and in murine acute colitis models.

Peritoneal cavity regulatory B cells (B10 cells) modulate IFN-γ+CD4+ T cell numbers during colitis development in mice

The spleen regulatory B cell subset with the functional capacity to express IL-10 (B10 cells) modulates both immune responses and autoimmune disease severity. However, the peritoneal cavity also contains relatively high frequencies of functionally defined IL-10-competent B10 cells. In this study, peritoneal cavity B10 cells shared similar cell surface phenotypes with their spleen counterparts. However, peritoneal cavity B10 cells were 10-fold more frequent among B cells than occurred within the spleen, intestinal tract, or mesenteric lymph nodes and were present at higher proportions among the phenotypically defined peritoneal B1a > B1b > B2 cell subpopulations. The development or localization of B10 cells within the peritoneal cavity was not dependent on the presence of commensal microbiota, T cells, IL-10 or B10 cell IL-10 production, or differences between their fetal liver or adult bone marrow progenitor cell origins. The BCR repertoire of peritoneal cavity B10 cells was diverse, as occurs in the spleen, and predominantly included germline-encoded VH and VL regions commonly found in either the conventional or B1 B cell compartments. Thereby, the capacity to produce IL-10 appears to be an intrinsic functional property acquired by clonally diverse B cells. Importantly, IL-10 production by peritoneal cavity B cells significantly reduced disease severity in spontaneous and induced models of colitis by regulating neutrophil infiltration, colitogenic CD4(+) T cell activation, and proinflammatory cytokine production during colitis onset. Thus, the numerically small B10 cell subset within the peritoneal cavity has regulatory function and is important for maintaining homeostasis within gastrointestinal tissues and the immune system.

Altered immune regulation in type 1 diabetes

Research in genetics and immunology was going on separate strands for a long time. Type 1 diabetes mellitus might not be characterized with a single pathogenetic factor. It develops when a susceptible individual is exposed to potential triggers in a given sequence and timeframe that eventually disarranges the fine-tuned immune mechanisms that keep autoimmunity under control in health. Genomewide association studies have helped to understand the congenital susceptibility, and hand-in-hand with the immunological research novel paths of immune dysregulation were described in central tolerance, apoptotic pathways, or peripheral tolerance mediated by regulatory T-cells. Epigenetic factors are contributing to the immune dysregulation. The interplay between genetic susceptibility and potential triggers is likely to play a role at a very early age and gradually results in the loss of balanced autotolerance and subsequently in the development of the clinical disease. Genetic susceptibility, the impaired elimination of apoptotic β-cell remnants, altered immune regulatory functions, and environmental factors such as viral infections determine the outcome. Autoreactivity might exist under physiologic conditions and when the integrity of the complex regulatory process is damaged the disease might develop. We summarized the immune regulatory mechanisms that might have a crucial role in disease pathology and development.

Regulatory B cells suppress imiquimod-induced, psoriasis-like skin inflammation

Psoriasis is an inflammatory cutaneous disorder characterized by marked epidermal thickening and Th1 and Th17 cell infiltration. At present, the contribution of B cells to the pathogenesis of psoriasis is unclear. In mice, topical application of imiquimod induces inflamed skin lesions and serves as an experimental animal model for human psoriasis. In this study, we showed that imiquimod-induced skin inflammation was more severe in CD19(-/-) than WT mice. These inflammatory responses were negatively regulated by a unique IL-10-producing CD1d(hi)CD5(+) regulatory B cell subset (B10 cells) that was absent in CD19(-/-) mice and represented only 1-2% of splenic B220(+) cells in WT mice. Splenic B10 cells entered the circulation and migrated to draining LNs during imiquimod-induced skin inflammation, thereby suppressing IFN-γ and IL-17 production. Furthermore, adoptive transfer of these B10 cells from WT mice reduced inflammation in CD19(-/-) mice. The present findings provide direct evidence that B10 cells regulate imiquimod-induced skin inflammation and offer insights into regulatory B cell-based therapies for the treatment of psoriasis.

Adaptive transfer of B10 cells: a novel therapy for chronic rejection after solid organ transplantation

Chronic rejection occurs between almost all MHC-mismatched donors and recipients after transplantation. Immunosuppressive agents have been administrated indiscriminately to manage potential rejection, but complications from lifelong immunosuppressive therapy threaten transplant recipients. Recent studies demonstrated that a number of regulatory B cells (B10 cells) negatively regulate T cell mediated immune responses without inducing systemic immune suppression. Therefore, we propose that adaptive transfer of B10 cells suppresses alloreactive CD8(+) cytotoxic T cell activation induced by allogeneic solid organ transplantation, reduces T cell mediated rejection and prolongs allograft survival.

IL-10-producing lymphocytes in inflammatory disease

IL-10 is an anti-inflammatory cytokine that plays a significant role in controlling inflammation and modulating adaptive immune responses that cause tissue damage. IL-10-producing lymphocytes contribute to the delicate balance between inflammation and immunoregulation, and are thus regarded as a kind of "regulatory cells." Dysregulation of these cells is linked with susceptibility to numerous inflammatory diseases. In this review, we summarized what is known about the regulatory effects of IL-10 produced by lymphocytes, including T cells, B cells and natural killer cells, in inflammatory diseases. We hope to augment immune responses or prevent immunopathology through making some small changes in the levels of IL-10 produced by lymphocytes, or in the cellular location where it is produced.

CD19 expression in B cells regulates atopic dermatitis in a mouse model

Atopic dermatitis is an inflammatory cutaneous disorder characterized by dry skin and relapsing eczematous skin lesions. Besides antibody production, the contribution of B cells to the pathogenesis of atopic dermatitis is unclear. In mice, repeated epicutaneous sensitization with ovalbumin induces inflamed skin lesions resembling human atopic dermatitis and therefore serves as an experimental model for this condition. To investigate the role of B cells in a murine model of atopic dermatitis, ovalbumin-sensitized allergic skin inflammation was assessed in mice lacking CD19. In ovalbumin-sensitized skin from CD19-deficient mice, the number of eosinophils and CD4(+) T cells was reduced, and both epidermal and dermal thickening were decreased. Following in vitro stimulation with ovalbumin, CD19 deficiency significantly reduced the proliferation of CD4(+), but not CD8(+), T cells from spleen and draining lymph nodes. Furthermore, splenocytes and draining lymph node cells from ovalbumin-sensitized CD19-deficient mice secreted significantly less IL-4, IL-13, and IL-17 than ovalbumin-sensitized wild-type mice. These results suggest that CD19 expression in B cells plays a critical role in antigen-specific CD4(+) T-cell proliferation and T helper 2 and 17 responses in a murine model of atopic dermatitis. Furthermore, the present findings may have implications for B-cell-targeted therapies for the treatment of atopic dermatitis.

B-cell linker protein expression contributes to controlling allergic and autoimmune diseases by mediating IL-10 production in regulatory B cells

BACKGROUND

Regulatory B cells that exhibit the cell-surface CD1d(hi)CD5(+) phenotype and produce IL-10 are termed B10 cells. Although B10 cells exert potent suppressive functions in patients with various allergic and autoimmunity disorders, the precise signaling mechanisms required for B10 cell functions remain unknown. B-cell linker protein (BLNK) is an essential component of the B-cell antigen receptor signaling pathway and is required for optimal B-cell development.

OBJECTIVE

We sought to elucidate the signaling pathways that are responsible for IL-10 production in B10 cells and in vivo mechanisms of how impaired B10 cell functions influence allergic and autoimmune responses.

METHOD

For in vitro assays, splenic CD1d(hi)CD5(+) B cells from BLNK-deficient (BLNK(-/-)) mice were analyzed for intracellular signaling pathways and cytokine production. Contact hypersensitivity (CHS) and experimental autoimmune encephalomyelitis were examined by using BLNK(-/-) mice.

RESULTS

Although the CD1d(hi)CD5(+) B-cell population was present in BLNK(-/-) mice, IL-10 production was impaired both in vitro and in vivo. BLNK(-/-) mice had exaggerated CHS and experimental autoimmune encephalomyelitis responses, which were normalized by adoptive transfer of splenic CD1d(hi)CD5(+) B cells from wild-type mice. In mice with CHS, BLNK(-/-) mice exhibited decreased B-cell and regulatory T-cell percentages and increased CD8(+) T-cell percentages in the skin and lymph nodes. In vitro BLNK was required for LPS-induced signal transducer and activator of transcription 3 phosphorylation in CD1d(hi)CD5(+) B cells. Finally, secreted IL-10 leads to autocrine expansion of IL-10-producing B cells.

CONCLUSION

BLNK serves as a critical signaling component for B10 cell function by mediating IL-10 production.

Donor-derived regulatory B cells are important for suppression of murine sclerodermatous chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is an increasingly frequent cause of morbidity and mortality of allogeneic hematopoietic stem-cell transplantation. Sclerodermatous cGVHD (Scl-cGVHD) is characterized by fibrosis and autoimmune features resembling those of systemic sclerosis (SSc). Transplantation of B10.D2 bone marrow and splenocytes into irradiated BALB/c mice is an established model of human Scl-cGVHD. To examine the role of B cells in Scl-cGVHD, CD19-deficient (CD19(-/-)) mice were used as donors or recipients. CD19(-/-) donors induced more severe Scl-cGVHD than wild-type donors, but use of CD19(-/-) recipients resulted in no significant differences compared with wild-type recipients. Moreover, CD19 deficiency on donor B cells resulted in the expansion of splenic interleukin (IL) -6-producing monocytes/macrophages, cytotoxic CD8(+) T cells, and Th1 cells during the early stage of disease and increased the infiltration of T cells, TGF-β-producing monocytes/macrophages, and Th2 cells into the skin in the later stage of Scl-cGVHD. IL-10-producing regulatory B cells (B10 cells) were not reconstituted by CD19(-/-) donor cells, and early adoptive transfer of B10 cells attenuated the augmented manifestations of CD19(-/-) donor-induced Scl-cGVHD. Therefore, donor-derived B10 cells have a suppressive role in Scl-cGVHD development, warranting future investigation of regulatory B-cell-based therapy for treatment of Scl-cGVHD and SSc.

IL-10-producing regulatory B cells (B10 cells) in autoimmune disease

B cell abnormalities contribute to the development and progress of autoimmune disease. Traditionally, the role of B cells in autoimmune disease was thought to be predominantly limited to the production of autoantibodies. Nevertheless, in addition to autoantibody production, B cells have other functions potentially relevant to autoimmunity. Such functions include antigen presentation to and activation of T cells, expression of co-stimulatory molecules and cytokine production. Recently, the ability of B cells to negatively regulate cellular immune responses and inflammation has been described and the concept of regulatory B cells has emerged. A variety of cytokines produced by regulatory B cell subsets have been reported, with IL-10 being the most studied. In this review, this specific IL-10-producing subset of regulatory B cells has been labeled B10 cells to highlight that the regulatory function of these rare B cells is mediated by IL-10, and to distinguish them from other B cell subsets that regulate immune responses through different mechanisms. B10 cells are a functionally defined subset currently identified only by their competency to produce and secrete IL-10 following appropriate stimulation. Although B10 cells share surface markers with other previously defined B cell subsets, currently there is no cell surface or intracellular phenotypic marker or set of markers unique to B10 cells. The recent discovery of an effective way to expand B10 cells ex vivo opens new horizons in the potential therapeutic applications of this rare B cell subset. This review highlights the current knowledge on B10 cells and discusses their potential as novel therapeutic agents in autoimmunity.

Regulatory B cell (B10 Cell) expansion during Listeria infection governs innate and cellular immune responses in mice

Pathogens use numerous methods to subvert host immune responses, including the modulation of host IL-10 production by diverse cell types. However, the B cell sources of IL-10 and their overall influence on innate and cellular immune responses have not been well characterized during infections. Using Listeria as a model pathogen, infection drove the acute expansion of a small subset of regulatory B cells (B10 cells) that potently suppress inflammation and autoimmunity through the production of IL-10. Unexpectedly, spleen bacteria loads were 92-97% lower in B10 cell-deficient CD19(-/-) mice, in mice depleted of mature B cells, and in mice treated with CD22 mAb to preferentially deplete B10 cells before infection. By contrast, the adoptive transfer of wild-type B10 cells reduced bacterial clearance by 38-fold in CD19(-/-) mice through IL-10-dependent pathways. B10 cell depletion using CD22 mAb significantly enhanced macrophage phagocytosis of Listeria and their production of IFN-γ, TNF-α, and NO ex vivo. Accelerated bacteria clearance following B10 cell depletion significantly reduced Ag-specific CD4(+) T cell proliferation and cytokine production, but did not alter CD8(+) T cell responses. B10 cell regulatory function during innate immune responses was nonetheless dependent on cognate interactions with CD4(+) T cells because B10 cells deficient in IL-10, MHC-II, or IL-21R expression did not influence Listeria clearance. Thus, Listeria manipulates immune responses through a strategy of immune evasion that involves the preferential expansion of endogenous B10 cells that regulate the magnitude and duration of both innate and cellular immune responses.

Decrease in proportion of CD19+ CD24(hi) CD27+ B cells and impairment of their suppressive function in Graves' disease

IL-10-producing B cells (B10 cells) have been shown to play a suppressive role in the peripheral blood of humans, with their numbers and function altered in several autoimmune diseases. However, the role of B10 cells in Graves' disease (GD) remains unknown. In this study, we demonstrated that B10 cells in human peripheral blood belonged to a CD24(hi)CD27(+) B cell subpopulation. The proportion of B10 cells along with the CD19(+)CD24(hi)CD27(+) B cell subset was significantly lower in new-onset patients compared with healthy individuals. In recovered patients, these proportions were restored to levels similar to those seen in healthy individuals. Additionally, we found that CD19(+)CD24(hi)CD27(+) B cells from healthy individuals inhibited proliferation and TNF-α production of CD4(+) T cells via an IL-10-independent pathway. They also inhibited IFN-γ production by CD4(+) T cells, through an IL-10-dependent pathway. In contrast, their suppressive function on CD4(+) T cell proliferation and cytokine production was impaired in new-onset and recovered patients compared with healthy individuals. Our study provides evidence that CD19(+)CD24(hi)CD27(+) B cells may possess the capacity to downregulate immune responses, partially by production of IL-10 in human peripheral blood. Impairment of their immunosuppressive function may contribute to GD pathogenesis and relapse.

The role of B lymphocytes in the progression from autoimmunity to autoimmune disease

Autoimmunity, defined as the presence of autoreactive T and/or B lymphocytes in the periphery, is a frequent and probably even physiological condition. It is mainly caused by the fact that the central tolerance mechanisms, which are responsible for counter-selection of autoreactive lymphocytes, are not perfect and thus a limited number of these autoreactive cells can mature and enter the periphery. Nonetheless, autoreactive cells do not lead automatically to autoimmune disease as evidenced by a multitude of experimental and human data sets. Interestingly, the progression from autoimmunity to autoimmune disease is not only determined by the degree of central tolerance leakage and thus the amount of autoreactive lymphocytes in the periphery, but also by peripheral mechanism of activation and control of the autoreactive cells. In this review, we discuss the contribution of peripheral B lymphocytes in this process, ranging from activation of T cells and epitope spreading to control of the autoimmune process by regulatory mechanisms. We also discuss the parallels with the role of B cells in the induction and control of alloimmunity in the context of organ transplantation, as more precise knowledge of the pathogenic antigens and time of initiation of the immune response in allo- versus auto-immunity allows better dissection of the exact role of B cells. Since peripheral mechanisms may be easier to modulate than central tolerance, a more thorough understanding of the role of peripheral B cells in the progression from autoimmunity to autoimmune disease may open new avenues for treatment and prevention of autoimmune disorders.

IL-10-producing regulatory B cells in the pathogenesis of chronic hepatitis B virus infection

A regulatory subset of B cells has been found to modulate immune responses in autoimmunity, infection, and cancer, but it has not been investigated in the setting of human persistent viral infection. IL-10 is elevated in patients with chronic hepatitis B virus infection (CHB), but its cellular sources and impact on antiviral T cells have not been addressed. We investigated the role of IL-10 and regulatory B cells in the pathogenesis of CHB. Serum IL-10 levels were studied longitudinally in patients with CHB undergoing spontaneous disease flares. There was a close temporal correlation between IL-10 levels and fluctuations in viral load or liver inflammation. Blockade of IL-10 in vitro rescued polyfunctional virus-specific CD8 T cell responses. To investigate the potential contribution of regulatory B cells, their frequency was measured directly ex vivo and after exposure to stimuli relevant to hepatitis B virus (HBV) (CpG or HBV Ags). IL-10-producing B cells were enriched in patients, and their frequency correlated temporally with hepatic flares, both after stimulation and directly ex vivo. Phenotypically, these cells were predominantly immature (CD19(+)CD24(hi)CD38(hi)) ex vivo; sorted CD19(+)CD24(hi)CD38(hi) cells suppressed HBV-specific CD8 T cell responses in an IL-10-dependent manner. In summary, these data reveal a novel IL-10-producing subset of B cells able to regulate T cell immunity in CHB.

Modulation of intestinal inflammation by yeasts and cell wall extracts: strain dependence and unexpected anti-inflammatory role of glucan fractions

Yeasts and their glycan components can have a beneficial or adverse effect on intestinal inflammation. Previous research has shown that the presence of Saccharomyces cerevisiae var. boulardii (Sb) reduces intestinal inflammation and colonization by Candida albicans. The aim of this study was to identify dietary yeasts, which have comparable effects to the anti-C. albicans and anti-inflammatory properties of Sb and to assess the capabilities of yeast cell wall components to modulate intestinal inflammation. Mice received a single oral challenge of C. albicans and were then given 1.5% dextran-sulphate-sodium (DSS) for 2 weeks followed by a 3-day restitution period. S. cerevisiae strains (Sb, Sc1 to Sc4), as well as mannoprotein (MP) and β-glucan crude fractions prepared from Sc2 and highly purified β-glucans prepared from C. albicans were used in this curative model, starting 3 days after C. albicans challenge. Mice were assessed for the clinical, histological and inflammatory responses related to DSS administration. Strain Sc1-1 gave the same level of protection against C. albicans as Sb when assessed by mortality, clinical scores, colonization levels, reduction of TNFα and increase in IL-10 transcription. When Sc1-1 was compared with the other S. cerevisiae strains, the preparation process had a strong influence on biological activity. Interestingly, some S. cerevisiae strains dramatically increased mortality and clinical scores. Strain Sc4 and MP fraction favoured C. albicans colonization and inflammation, whereas β-glucan fraction was protective against both. Surprisingly, purified β-glucans from C. albicans had the same protective effect. Thus, some yeasts appear to be strong modulators of intestinal inflammation. These effects are dependent on the strain, species, preparation process and cell wall fraction. It was striking that β-glucan fractions or pure β-glucans from C. albicans displayed the most potent anti-inflammatory effect in the DSS model.

Host-microbiota interactions in inflammatory bowel disease

The interaction of the host with its abundant intestinal microbiota is complex and engages most of the cells in the intestinal mucosa. The inflammatory bowel diseases appear to be disorders of the host immune response to the microbiota. This is supported by data from induced gene mutations in mice and more recently by the identification of gene variants in humans that result in IBD or IBD susceptibility. These genetic studies have provided insights into the cells and molecular pathways involved in the host-microbiota dialog. This review discusses the innate, adaptive, and regulatory immune response to the microbiota in the context of the mouse and human genes that are involved in maintaining intestinal homeostasis and preventing inflammation. These data continue to support the hypothesis that inflammatory bowel disease results from a dysregulated adaptive immune response, particularly a CD4 T-cell response, to the microbiota. The microbiota itself is an active participant in these homeostatic processes. The microbiota composition is perturbed during inflammation, resulting in a dysbiosis that may induce or perpetuate inflammation. However, host genotype and the environment have a major impact on the shape of such dysbiosis, as well as upon which members of the microbiota stimulate pathogenic immune responses.

A protective role for human IL-10-expressing CD4+ T cells in colitis

IL-10 is an immunoregulatory cytokine expressed by numerous cell types. Studies in mice confirm that different IL-10-expressing cell subsets contribute differentially to disease phenotypes. However, little is known about the relationship between cell- or tissue-specific IL-10 expression and disease susceptibility in humans. In this study, we used the previously described human (h)IL10BAC transgenic model to examine the role of hIL-10 in maintaining intestinal homeostasis. Genomically controlled hIL-10 expression rescued Il10(-/-) mice from Helicobacter-induced colitis and was associated with control of proinflammatory cytokine expression and Th17 cell accumulation in gut tissues. Resistance to colitis was associated with an accumulation of hIL-10-expressing CD4(+)Foxp3(+) regulatory T cells specifically within the lamina propria but not other secondary lymphoid tissues. Cotransfer of CD4(+)CD45RB(lo) cells from Il10(-/-)/hIL10BAC mice rescued Rag1(-/-) mice from colitis, further suggesting that CD4(+) T cells represent a protective source of hIL-10 in the colon. In concordance with an enhanced capacity to express IL-10, CD4(+)CD44(+) T cells isolated from the lamina propria exhibited lower levels of the repressive histone mark H3K27Me3 and higher levels of the permissive histone mark acetylated histone H3 in both the human and mouse IL10 locus compared with the spleen. These results provide experimental evidence verifying the importance of T cell-derived hIL-10 expression in controlling inflammation within the colonic mucosa. We also provide molecular evidence suggesting the tissue microenvironment influences IL-10 expression patterns and chromatin structure in the human (and mouse) IL10 locus.

Pulsed high-dose dexamethasone improves interleukin 10 secretion by CD5+ B cells in patients with primary immune thrombocytopenia

BACKGROUND

B cells expressing CD5 are potentially capable of producing interleukin 10 (IL-10) which contributes to the regulatory function of B cells. This study was aimed at exploring the alteration of numbers of CD5(+) B cells and their ability of producing IL-10 in patients with immune thrombocytopenia (ITP), and the effects of pulsed high-dose dexamethasone (HD-DXM) therapy on CD5(+) B cells.

METHODS

Peripheral blood mononuclear cells from 25 adult ITP patients were stained with PE-CD5/FITC-CD19 antibodies for flow cytometry analyses before and after HD-DXM therapy. The expression of IL-10 mRNA was measured by RT-PCR. After 24 h culture with or without dexamethasone in the presence of PMA, ionomycin and Brefeldin A, cells were permeabilized and stained with APC-IL-10 antibody to investigate intracellular IL-10 expression. Supernatant IL-10 concentration was detected by ELISA.

RESULTS

The number of CD5(+) B cells was elevated in patients with ITP. Expression of IL-10 mRNA, percentage of IL-10(+) cells and intracellular IL-10 in CD5(+) B cells from untreated patients were significantly higher than that in controls. In contrast, ITP patients showed lower IL-10 concentration in supernatants than controls. After HD-DXM therapy, the number of CD5(+) B cells decreased to normal level, while intracellular IL-10 expression in CD5(+) B cells was further enhanced and IL-10 concentration in supernatants was also increased. Similar results were observed when dexamethasone was administrated in vitro.

CONCLUSIONS

Increased number of CD5(+) B cells in which IL-10 is accumulated with decreased IL-10 concentration in supernatants suggests that the ability of CD5(+) B cells to secret IL-10 is impaired in ITP patients. Both the aberrant number and ability of IL-10 secretion of CD5(+) B cells could be corrected by HD-DXM.

Reprogramming of B cells into regulatory cells with engineered fusokines

B cells play a pivotal role in host adaptive immunity against pathogenic microorganisms, but may also maladaptively contribute to the pathogenesis of autoimmune diseases. In contrast, distinct B cell subsets have the capacity to regulate host immune response, and suppress inflammation. B regulatory cells are a rare population of endogenous Blymphocytes defined in part by production of the anti-inflammatory cytokine IL-10. Although "natural" B regulatory cells exist in vivo, the low frequency of B regulatory cells may be a limiting factor on their impact in autoimmune ailments. In answer to this unmet need, we have developed a novel strategy for alternate lymphoid activation: fusokines. These wholly engineered chimeric leukines fuse two functionally unrelated cytokines for the purpose of alternate immune modulation. The GM-CSF- and IL-15-derived fusokine: GIFT15, possesses entirely novel and unheralded immune modulating properties mediated through the IL15 receptor which reprograms naive B cells into B regulatory cells (Bregs). In this article, we review the current approaches to generate Bregs in vitro, and highlight gain-of-function mechanisms by which GIFT15- induced Bregs abrogate pathogenic autoimmunity in mice. We also demonstrate that the human equivalent of inducible Bregs may also serve as a new potent therapeutic tool for treatment of autoimmune disease.

A novel IL-10-independent regulatory role for B cells in suppressing autoimmunity by maintenance of regulatory T cells via GITR ligand

B cells are important for the regulation of autoimmune responses. In experimental autoimmune encephalomyelitis (EAE), B cells are required for spontaneous recovery in acute models. Production of IL-10 by regulatory B cells has been shown to modulate the severity EAE and other autoimmune diseases. Previously, we suggested that B cells regulated the number of CD4(+)Foxp3(+) T regulatory cells (Treg) in the CNS during EAE. Because Treg suppress autoimmune responses, we asked whether B cells control autoimmunity by maintenance of Treg numbers. B cell deficiency achieved either genetically (μMT) or by depletion with anti-CD20 resulted in a significant reduction in the number of peripheral but not thymic Treg. Adoptive transfer of WT B cells into μMT mice restored both Treg numbers and recovery from EAE. When we investigated the mechanism whereby B cells induce the proliferation of Treg and EAE recovery, we found that glucocorticoid-induced TNF ligand, but not IL-10, expression by B cells was required. Of clinical significance is the finding that anti-CD20 depletion of B cells accelerated spontaneous EAE and colitis. Our results demonstrate that B cells play a major role in immune tolerance required for the prevention of autoimmunity by maintenance of Treg via their expression of glucocorticoid-induced TNFR ligand.

B cells exposed to enterobacterial components suppress development of experimental colitis

BACKGROUND

B cells positively contribute to immunity by antigen presentation to CD4(+) T cells, cytokine production, and differentiation into antibody secreting plasma cells. Accumulating evidence implies that B cells also possess immunoregulatory functions closely linked to their capability of IL-10 secretion.

METHODS

Colitis development was followed in CD4(+) CD25(-) T cell transplanted SCID mice co-transferred with B cells exposed to an enterobacterial extract (ebx-B cells). B and T cell cytokine expression was measured by flow cytometry and enzyme-linked immunosorbent assay (ELISA).

RESULTS

We demonstrate that splenic B cells exposed to ebx produce large amounts of IL-10 in vitro and express CD1d and CD5 previously known to be associated with regulatory B cells. In SCID mice transplanted with colitogenic CD4(+) CD25(-) T cells, co-transfer of ebx-B cells significantly suppressed development of colitis. Suppression was dependent on B cell-derived IL-10, as co-transfer of IL-10 knockout ebx-B cells failed to suppress colitis. Ebx-B cell-mediated suppression of colitis was associated with a decrease in interferon gamma (IFN-γ)-producing T(H) 1 cells and increased frequencies of Foxp3-expressing T cells.

CONCLUSIONS

These data demonstrate that splenic B cells exposed to enterobacterial components acquire immunosuppressive functions by which they can suppress development of experimental T cell-mediated colitis in an IL-10-dependent way.

Soy-derived di- and tripeptides alleviate colon and ileum inflammation in pigs with dextran sodium sulfate-induced colitis

We evaluated the antiinflammatory activity of soy-derived di- and tripeptides in a dextran sodium sulfate (DSS)-induced pig model of intestinal inflammation. In the DSS-positive control (POS) and DSS-positive with soy peptide treatment (SOY) groups (n = 6/group), DSS was administered to piglets via i.g. catheter for 5 d, followed by a 5-d administration of saline or soy-derived peptides, respectively. A negative control (NEG) group received saline in lieu of the DSS and soy peptides. The severity of inflammation was assessed by clinical signs, morphological and histological measurements, gut permeability, and neutrophil infiltration. Local production of TNF and IL6 were measured by ELISA, colonic and ileal inflammatory gene expression were assessed by real-time RT-PCR, and CD4+CD25+ lymphocyte populations were analyzed by flow cytometry. Crypt elongation and muscle thickness, d-mannitol gut permeation, colonic expression of the inflammatory mediators IFNG, IL1B, TNF, RORC, and IL17A as well as the FOXP3 T-regulatory transcription factor, and myeloperoxidase activity were lower (P < 0.05) in the SOY pigs than in POS pigs. Messenger RNA levels of ileal IFNG, TNF, IL12B, and IL17A were lower (P < 0.05) and FOXP3 expression was greater (P < 0.05) in SOY piglets than in the POS group. In the mesenteric lymph nodes, CD4+CD25+ T cells were higher (P < 0.05) in both the POS and SOY groups than in NEG controls. Soy-derived peptides exert antiinflammatory activity in vivo, suggesting their usefulness for the treatment of inflammatory disorders.

Perioperative dynamic alterations in peripheral regulatory T and B cells in patients with hepatocellular carcinoma

Background

Intratumoral and circulating regulatory T cells (Tregs) have been shown to be critical in the pathogenesis of hepatocellular carcinoma (HCC). However there is limited knowledge on the alterations of regulatory B cells (Bregs). We here investigated perioperative dynamic alterations of peripheral circulating Tregs and Bregs in HCC patients to reveal the relationship between regulatory lymphocytes and its clinical implications.

Methods

36 patients with HCC, 6 with chronic hepatitis B infection and 10 healthy donors were enrolled for this study. Frequencies of peripheral Tregs and Bregs were measured by flow cytometry with antibodies against CD4, CD25, CD127, CD19 and IL-10 before, and after radical surgery. Then, clinical informatics of HCC patients was achieved through Digital Evaluation Score System (DESS) for the assessment of disease severity. Finally, we analysed correlations between digitalized clinical features and kinetics of circulating regulatory lymphocytes.

Results

Level of circulating CD4⁺CD25⁺CD127^- Tregs in HCC patients was significantly lower than that in healthy donors and patients with chronic hepatitis B infection before surgery, but was increased after surgery. Preoperative level of CD19⁺ IL-10⁺ Bregs in HCC patients was also significantly lower than the other groups. However it dramatically was elevated right after surgery and remained elevated compared to controls (about 7 days after surgery, P = 0.04). Frequency of circulating Tregs was correlated with circulating leukocytes, ferritin, and clinical features suggesting tumor aggressiveness including portal vein thrombosis, hepatic vein involvement and advanced clinical stages. Frequency of circulating Bregs was associated with Hepatitis B e Antigen (HBeAg) and Hepatitis B virus (HBV) DNA copy number. In addition, DESS was significantly and positively correlated with other staging systems.

Conclusion

Frequencies of peripheral Tregs and Bregs in HCC patients increased after surgery. These results suggest that a postoperative combination of therapies against Tregs and Bregs may be beneficial for better outcome of HCC patients after resection.