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

5-HT induces regulatory B cells in fighting against inflammation-driven ulcerative colitis

Serotonin (5-hydroxytryptamine or 5-HT) is a neuroendocrine peptide endowed with immunomodulatory functions. Regulatory B cells (Bregs) play an important role in maintaining intestinal immune homeostasis. We analyzed the differences of 5-HT and Bregs between peripheral blood of ulcerative colitis (UC) and healthy controls (HC). Besides, 5-HT-treated B cells were adoptively transferred into colitis mice to elucidate the role of 5-HT in regulating Bregs. The level of serum 5-HT and IL-10 in UC patients was lower and both were negatively correlated with disease activity. 5-HT7 receptor (5-HT7R) was higher expressed on Bregs in UC. 5-HT promoted IL-10 production in Bregs through the activation of STAT3. And adoptive transfer of 5-HT-treated B cells alleviated intestinal inflammation via inducing IL-10-producing B cells in mice. Our results suggest that 5-HT/5-HT7R signaling pathway facilitate functional Bregs in constraining inflammation in UC, which may be a new potential prospect in the treatment of UC.

Effect of thymectomy on the frequencies of peripheral regulatory B and T lymphocytes in patients with Myasthenia gravis-a pilot study

AIM

We aimed to investigate the relationship between the peripheral lymphocyte subset frequency and thymectomy in patients with myasthenia gravis (MG).

MATERIALS AND METHODS

The frequencies of regulatory B (Breg) and regulatory T (Treg) cells in peripheral blood samples obtained from 69 patients with MG and 10 healthy controls were analyzed using flow cytometry. Serum acetylcholine receptor antibodies (AchR-Ab) were measured. Patients with MG were subdivided into pre-thymectomy, post-thymectomy, and normal thymus control group.

RESULTS

The percentage of Breg cells was significantly decreased in both the pre-thymectomy (7.92 ± 1.30%) and post-thymectomy (8.14 ± 1.34%) groups compared to healthy controls (16.02 ± 2.78%) and reduced in the exacerbation and relapse phase compared to the stable maintenance stage. The proportion of cluster of differentiation (CD) 4 + CD25 + T cells and CD4 + CD25 + CD127low/- Treg cells in MG patients were not significantly different than healthy controls. AchR-Ab titers in aggravating or recurrence patients after thymectomy were significantly higher than that of the stable remission patients (11.13 ± 0.70 and 6.03 ± 0.85 nmol/L, respectively; p < 0.001).

CONCLUSION

The frequency of Breg cells may serve as a potential indicator of MG prognosis, while Treg cell frequency did not demonstrate the same prognostic ability. The concentration of AchR-Ab can be used as a dynamic monitoring index of disease severity in patients with MG.

Microbial-Immune Crosstalk in Elderly-Onset Inflammatory Bowel Disease: Unchartered Territory

Elderly-onset inflammatory bowel disease [IBD] patients exhibit a distinct natural history compared to younger IBD patients, with unique disease phenotypes, differential responses to therapy, and increased surgical morbidity and mortality. Despite the foreseeable high demand for personalized medicine and specialized IBD care in the elderly, current paradigms of IBD management fail to capture the required nuances of care for elderly-onset IBD patients. Our review postulates the roles of systemic and mucosal immunosenescence, inflammageing and a dysbiotic microbial ecosystem in the pathophysiology of elderly-onset IBD. Ultimately, a better understanding of elderly-onset IBD can lead to improved patient outcomes and the tailoring of future preventative and treatment strategies.

The Underappreciated Role of Secretory IgA in IBD

Eighty percent of antibody secreting cells (ASCs) are found in the intestine, where they produce grams of immunoglobulin (Ig) A daily. immunoglobulin A is actively transcytosed into the lumen, where it plays a critical role in modulating the gut microbiota. Although loss of immune tolerance to bacterial antigens is the likely trigger of the dysregulated immune response that characterizes inflammatory bowel disease (IBD), little effort has been placed on understanding the interface between B cells, IgA, and the microbiota during initiation or progression of disease. This may be in part due to the misleading fact that IgA-deficient humans are mostly asymptomatic, likely due to redundant role of secretory (S) IgM. Intestinal B cell recruitment is critically dependent on integrin α4β7-MAdCAM-1 interactions, yet antibodies that target α4β7 (ie, vedolizumab), MAdCAM-1 (ie, ontamalimab), or both β7 integrins (α4β7 and αE [CD103] β7; etrolizumab) are in clinical use or development as IBD therapeutics. The effect of such interventions on the biology of IgA is largely unknown, yet a single dose of vedolizumab lowers SIgA levels in stool and weakens the oral immunization response to cholera vaccine in healthy volunteers. Thus, it is critical to further understand the role of these integrins for the migration of ASC and other cellular subsets during homeostasis and IBD-associated inflammation and the mode of action of drugs that interfere with this traffic. We have recently identified a subset of mature ASC that employs integrin αEβ7 to dock with intestinal epithelial cells, predominantly in the pericryptal region of the terminal ileum. This role for the integrin had not been appreciated previously, nor the αEβ7-dependent mechanism of IgA transcytosis that it supports. Furthermore, we find that B cells more than T cells are critically dependent on α4β7-MAdCAM-1 interactions; thus MAdCAM-1 blockade and integrin-β7 deficiency counterintuitively hasten colitis in interleukin-10-deficient mice. In both cases, de novo recruitment of IgA ASC to the intestinal lamina propria is compromised, leading to bacterial overgrowth, dysbiosis, and lethal colitis. Thus, despite the safe and effective use of anti-integrin antibodies in patients with IBD, much remains to be learned about their various cell targets.

Therapeutic potential of mesenchymal stem/stromal cells (MSCs)-based cell therapy for inflammatory bowel diseases (IBD) therapy

Recently, mesenchymal stem/stromal cells (MSCs) therapy has become an emerging therapeutic modality for the treatment of inflammatory bowel disease (IBD), given their immunoregulatory and pro-survival attributes. MSCs alleviate dysregulated inflammatory responses through the secretion of a myriad of anti-inflammatory mediators, such as interleukin 10 (IL-10), transforming growth factor-β (TGFβ), prostaglandin E2 (PGE2), tumor necrosis factor-stimulated gene-6 (TSG-6), etc. Indeed, MSC treatment of IBD is largely carried out through local microcirculation construction, colonization and repair, and immunomodulation, thus alleviating diseases severity. The clinical therapeutic efficacy relies on to the marked secretion of various secretory molecules from viable MSCs via paracrine mechanisms that are required for gut immuno-microbiota regulation and the proliferation and differentiation of surrounding cells like intestinal epithelial cells (IECs) and intestinal stem cells (ISCs). For example, MSCs can induce IECs proliferation and upregulate the expression of tight junction (TJs)-associated protein, ensuring intestinal barrier integrity. Concerning the encouraging results derived from animal studies, various clinical trials are conducted or ongoing to address the safety and efficacy of MSCs administration in IBD patients. Although the safety and short-term efficacy of MSCs administration have been evinced, the long-term efficacy of MSCs transplantation has not yet been verified. Herein, we have emphasized the illumination of the therapeutic capacity of MSCs therapy, including naïve MSCs, preconditioned MSCs, and also MSCs-derived exosomes, to alleviate IBD severity in experimental models. Also, a brief overview of published clinical trials in IBD patients has been delivered.

The emerging role of regulatory cell-based therapy in autoimmune disease

Autoimmune disease, caused by unwanted immune responses to self-antigens, affects millions of people each year and poses a great social and economic burden to individuals and communities. In the course of autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes mellitus, and multiple sclerosis, disturbances in the balance between the immune response against harmful agents and tolerance towards self-antigens lead to an immune response against self-tissues. In recent years, various regulatory immune cells have been identified. Disruptions in the quality, quantity, and function of these cells have been implicated in autoimmune disease development. Therefore, targeting or engineering these cells is a promising therapeutic for different autoimmune diseases. Regulatory T cells, regulatory B cells, regulatory dendritic cells, myeloid suppressor cells, and some subsets of innate lymphoid cells are arising as important players among this class of cells. Here, we review the roles of each suppressive cell type in the immune system during homeostasis and in the development of autoimmunity. Moreover, we discuss the current and future therapeutic potential of each one of these cell types for autoimmune diseases.

Suppressive mechanisms of regulatory B cells in mice and humans

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

Regulatory B cell repertoire defects predispose lung cancer patients to immune-related toxicity following checkpoint blockade

Checkpoint blockade with Pembrolizumab, has demonstrated durable clinical responses in advanced non-small cell lung cancer, however, treatment is offset by the development of high-grade immune related adverse events (irAEs) in some patients. Here, we show that in these patients a deficient Breg checkpoint fails to limit self-reactive T cell enhanced activity and auto-antibody formation enabled by PD-1/PD-L1 blockade, leading to severe auto-inflammatory sequelae. Principally a failure of IL-10 producing regulatory B cells as demonstrated through functional ex vivo assays and deep phenotyping mass cytometric analysis, is a major and significant finding in patients who develop high-grade irAEs when undergoing treatment with anti-PD1/PD-L1 checkpoint blockade. There is currently a lack of biomarkers to identify a priori those patients at greatest risk of developing severe auto-inflammatory syndrome. Pre-therapy B cell profiling could provide an important tool to identify lung cancer patients at high risk of developing severe irAEs on checkpoint blockade.

Intraperitoneally Delivered Mesenchymal Stem Cells Alleviate Experimental Colitis Through THBS1-Mediated Induction of IL-10-Competent Regulatory B Cells

Mesenchymal stem cells (MSCs) show promising therapeutic potential in treating inflammatory bowel disease (IBD), and intraperitoneal delivery of MSCs have become a more effective route for IBD treatment. However, the underlying mechanisms are still poorly understood. Here, we found that intraperitoneally delivered MSCs significantly alleviated experimental colitis. Depletion of peritoneal B cells, but not macrophages, clearly impaired the therapeutic effects of MSCs. Intraperitoneally delivered MSCs improved IBD likely by boosting the IL-10-producing B cells in the peritoneal cavity, and a single intraperitoneal injection of MSCs could significantly prevent disease severity in a recurrent mouse colitis model, with lower proinflammation cytokines and high level of IL-10. The gene expression profile revealed that thrombospondin-1 (THBS1) was dramatically upregulated in MSCs after coculture with peritoneal lavage fluid from colitis mice. Knockout of THBS1 expression in MSCs abolished their therapeutic effects in colitis and the induction of IL-10-producing B cells. Mechanistically, THBS1 modulates the activation of transforming growth factor-β (TGF-β), which combines with TGF-β receptors on B cells and contributes to IL-10 production. Blocking the interaction between THBS1 and latent TGF-β or inhibiting TGF-β receptors (TGF-βR) significantly reversed the THBS1-mediated induction of IL-10-producing B cells and the therapeutic effects on colitis. Collectively, our study revealed that intraperitoneally delivered MSCs secreted THBS1 to boost IL-10⁺Bregs and control the progression and recurrence of colitis, providing new insight for the prevention and treatment of IBD.

Defective humoral immunity disrupts bile acid homeostasis which promotes inflammatory disease of the small bowel

Mucosal antibodies maintain gut homeostasis by promoting spatial segregation between host tissues and luminal microbes. Whether and how mucosal antibody responses influence gut health through modulation of microbiota composition is unclear. Here, we use a CD19^-/- mouse model of antibody-deficiency to demonstrate that a relationship exists between dysbiosis, defects in bile acid homeostasis, and gluten-sensitive enteropathy of the small intestine. The gluten-sensitive small intestine enteropathy that develops in CD19^-/- mice is associated with alterations to luminal bile acid composition in the SI, marked by significant reductions in the abundance of conjugated bile acids. Manipulation of bile acid availability, adoptive transfer of functional B cells, and ablation of bacterial bile salt hydrolase activity all influence the severity of small intestine enteropathy in CD19^-/- mice. Collectively, results from our experiments support a model whereby mucosal humoral immune responses limit inflammatory disease of the small bowel by regulating bacterial BA metabolism.

Interleukin-35 Prevents Development of Autoimmune Diabetes Possibly by Maintaining the Phenotype of Regulatory B Cells

The anti-inflammatory role of regulatory B cells (Breg cells) has been associated with IL-35 based on studies of experimental autoimmune uveitis and encephalitis. The role of Breg cells and IL-35⁺ Breg cells for type 1 diabetes (T1D) remains to be investigated. We studied PBMCs from T1D subjects and healthy controls (HC) and found lowered proportions of Breg cells and IL-35⁺ Breg cells in T1D. To elucidate the role of Breg cells, the lymphoid organs of two mouse models of T1D were examined. Lower proportions of Breg cells and IL-35⁺ Breg cells were found in the animal models of T1D compared with control mice. In addition, the systemic administration of recombinant mouse IL-35 prevented hyperglycemia after multiple low dose streptozotocin (MLDSTZ) injections and increased the proportions of Breg cells and IL-35⁺ Breg cells. A higher proportion of IFN-γ⁺ cells among Breg cells were found in the PBMCs of the T1D subjects. In the MLDSTZ mice, IL-35 administration decreased the proportions of IFN-γ⁺ cells among the Breg cells. Our data illustrate that Breg cells may play an important role in the development of T1D and that IL-35 treatment prevents the development of hyperglycemia by maintaining the phenotype of the Breg cells under an experimental T1D condition.

Regulatory B Cells in Autoimmune Diabetes

Since they were discovered almost three decades ago, a subset of B cells denoted as regulatory B cells (Bregs) have elicited interest throughout the immunology community. Many investigators have sought to characterize their phenotype and to understand their function and immunosuppressive mechanisms. Indeed, studies in murine models have demonstrated that Bregs possess varied phenotypic markers and could be classified into different subsets whose action and pivotal role depend on the pathological condition or stimuli. Similar conclusions were drawn in clinical settings delineating an analogous Breg population phenotypically resembling the murine Bregs that ultimately may be associated with a state of tolerance. Recent studies suggested that Bregs may play a role in the onset of autoimmune diabetes. This review will focus on deciphering the different subclasses of Bregs, their emerging role in autoimmune diabetes, and their potential use as a cell-based therapeutic.

Advances of Regulatory B Cells in Autoimmune Diseases

With the ability to induce T cell activation and elicit humoral responses, B cells are generally considered as effectors of the immune system. However, the emergence of regulatory B cells (Bregs) has given new insight into the role of B cells in immune responses. Bregs exhibit immunosuppressive functions via diverse mechanisms, including the secretion of anti-inflammatory cytokines and direct cell contact. The balance between Bregs and effector B cells is important for the immune tolerance. In this review, we focus on recent advances in the characteristics of Bregs and their functional roles in autoimmunity.

Distribution and Cytokine Profile of Peripheral B Cell Subsets Is Perturbed in Pediatric IBD and Partially Restored During a Successful IFX Therapy

BACKGROUND

The role of B cells in inflammatory bowel disease (IBD) is ambiguous, as B cells may have both pathogenic and protective functions in IBD. We studied B cell subsets before and after initiation of an anti-tumor necrosis factor alpha (anti-TNFα) therapy in pediatric IBD. The aim of the study was to examine the behavior of B cells in pediatric IBD patients undergoing an anti-TNFα therapy and, more specifically, to clarify their association with a successful or an unsuccessful infliximab (IFX) treatment.

METHODS

A total of N = 42 pediatric IBD patients (Crohn disease, n = 30; ulcerative colitis, n = 12) for whom an anti-TNFα therapy with and without a concomitant azathioprine (AZA) medication was administered were recruited. Fourteen healthy age-matched children served as control patients. Blood samples were collected before initiation of the anti-TNFα therapy, before the fourth infusion at the end of the induction phase, and after 6 and 12 months under therapy maintenance. Flow cytometry (CD20, CD27, CD38, CD138) and intracellular staining (interleukin 10 [IL10], TNFα, granzyme B) were performed. Responders to successful IFX therapy were classified exhibiting a fecal calprotectin level of below 100 µg/g or achieving levels of <10% of the baseline value at initiation than at the end of the 12-month follow-up period.

RESULTS

Before initiation of anti-TNFα therapy, flow cytometry revealed increased percentages of naïve B cells whereas transitional B cells were reduced compared with those in the healthy control patients. The IL10-producing B cells of both ulcerative colitis and Crohn disease patients were reduced at the initiation of IFX therapy, whereas TNFα-producing transitional CD24hiCD38hi B cells in ulcerative colitis patients were increased compared with those in healthy control patients. After 12 months of therapy, we detected a significant increase of IL10-producing transitional B cells in responding patients.The IFX trough levels in the responding patients showed a significant increase until 6 months after IFX initiation, attaining mean values of 9.9 µg/mL, whereas the IFX dosage was significantly lower than that in the nonresponding patients. The IFX trough levels in AZA-treated patients reached earlier therapeutic levels than in patients without AZA comedication, whereas during the course of the IFX therapy, comedication with AZA had no significant effect on the outcome.

CONCLUSIONS

Attaining a normalization of IL10 production among CD24hiCD38hi B cells after 12 months of therapy may represent additional information about the reconstitution of a patient's immune system in responding patients. The achievement of an IFX trough level of ~10 µg/mL at 6 months of treatment is associated with a successful anti-TNFα therapy. In addition, AZA comedication supports an earlier achievement of therapeutic IFX trough levels.

B-Cell Commitment to IL-10 Production: The VertX Il10egfp Mouse

Although the inflammatory cytokine IL-10 is pivotal in regulatory B-cell function, detecting IL-10-producing B cells by intracellular IL-10 staining requires multiple steps and tedious preparation. In contrast, the Il10-eGFP reporter mouse model (VertX), generated in 2009, allows easier and quicker detection of IL-10-producing B cells with the possibility of sorting viable cells without membrane permeabilization and ex vivo activation. Even though detecting IL-10⁺ cells is simpler, several nuances are important. For example, methanol-containing buffers delete GFP signal, while long-term fixation can maintain GFP intensity but decreases other intracellular signals (FOXP3, etc.). Here, we provide optimized and improved protocols for GFP detection in intestinal B cells and isolation techniques of lamina propria, spleen, mesenteric lymph node, peritoneum, and blood cells from VertX mice.

Antigen presentation, autoantibody production, and therapeutic targets in autoimmune liver disease

The liver is an important immunological organ that controls systemic tolerance. The liver harbors professional and unconventional antigen-presenting cells that are crucial for tolerance induction and maintenance. Orchestrating the immune response in homeostasis depends on a healthy and well-toned immunological liver microenvironment, which is maintained by the crosstalk of liver-resident antigen-presenting cells and intrahepatic and liver-infiltrating leukocytes. In response to pathogens or autoantigens, tolerance is disrupted by unknown mechanisms. Intrahepatic parenchymal and nonparenchymal cells exhibit unique antigen-presenting properties. The presentation of microbial and endogenous lipid-, metabolite- and peptide-derived antigens from the gut via conventional and nonconventional mechanisms can educate intrahepatic immune cells and elicit effector responses or tolerance. Perturbation of this balance results in autoimmune liver diseases, such as autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis. Although the exact etiologies of these autoimmune liver diseases are unknown, it is thought that the disruption of tolerance towards self-antigens and microbial metabolites and lipids, as well as alterations in bile acid composition, may result in changes in effector cell activation and polarization and may reduce or impair protective anti-inflammatory regulatory T and B cell responses. Additionally, the canonical and noncanonical transmission of antigens and antigen:MHC complexes via trogocytosis or extracellular vesicles between different (non) immune cells in the liver may play a role in the induction of hepatic inflammation and tolerance. Here, we summarize emerging aspects of antigen presentation, autoantibody production, and the application of novel therapeutic approaches in the characterization and treatment of autoimmune liver diseases.

Role of regulatory B cells in autoimmune diseases of the digestive system

Recently, regulatory B cells (Breg), a subset of functional B cells, have been reported to participate in the negative regulation of immunity in autoimmune diseases by producing interleukin (IL)-10, IL-35, and transforming growth factor-β. However, a specific surface marker for Breg has not been identified and their potential therapeutic role requires further study. This review discusses the function of Breg in autoimmune diseases of the digestive system, with the purpose of highlighting their regulation of immune responses and their potential as a therapeutic target for the treatment of these diseases.

H.pylori Infection Alleviates Acute and Chronic Colitis with the Expansion of Regulatory B Cells in Mice

Epidemiological studies showed that there was an inverse relationship between Helicobacter pylori (H. pylori) infection and the incidence of inflammatory bowel diseases (IBD). Our previous research indicated that the regulatory immune responses induced by H. pylori infection were not limited to gastric mucosa, and the balance of intestinal mucosal immunity was influenced. In this study, mice were infected with H. pylori SS1, and then colitis was induced by 3% dextran sulphate sodium (DSS), to investigate the role of the regulatory B cells in the effects of H. pylori infection on acute and chronic colitis. In acute and chronic colitis groups, DAI and colonic histological scores reduced significantly and colon length shorted less, the proinflammatory cytokines mRNA expression downregulated in colonic mucosa, and the percentages of CD19⁺IL-10⁺Breg cells were higher in the H. pylori/DSS co-treated groups compared with the DSS-treated groups. Our study suggests that H. pylori infection can alleviate the acute and chronic colitis induced by DSS, and CD19⁺IL-10⁺Breg cells may play a critical role in the alleviation of acute and chronic colitis following H. pylori infection.

B cells in Crohn's patients presented reduced IL-35 expression capacity

Interleukin (IL)-35 has capacity to ameliorate experimental colitis and is upregulated in immune cells from active Crohn's disease (CD) patients. Nonetheless, CD continues to be an incurable disease with characteristics of chronic relapsing-remitting inflammation. In this study, we investigated the production of IL-35 by B cells from active CD patients and non-CD controls. Immediately ex vivo, the mRNA transcription of IL-12/IL-35 subunit IL12A was significantly higher in CD B cells than in control B cells, and the mRNA transcription of IL-27/IL-35 subunit EBI3 was significantly higher in mild CD and moderate CD B cells than in control B cells. However, we also found that CpG-activated B cells and BCR + CD40-activated B cells from CD subjects presented significantly lower IL12A and lower EBI3 transcription than their counterparts from control subjects. We further evaluated IL-35 protein secretion and confirmed that B cell-mediated IL-35 protein secretion was lower in CD patients than in controls. However, IL-35-Fc preconditioning was able to significantly increase IL-35 production from B cells and to eliminate the difference in IL-35 production capacity between controls and CD patients. Furthermore, these IL-35-Fc-preconditioned B cells were able to suppress IFN-γ and IL-17 production from CD4⁺CD25^- T cells more potently than Fc control-preconditioned B cells. Rh IL-27Rα-Fc, a soluble form of B cell-specific IL-35 receptor, significantly increased IFN-γ and IL-17 production. Together, these data supported a role of B cell-mediated IL-35 in suppressing IFN-γ and IL-17 inflammation. However, despite the fact that CD B cells presented higher transcription of IL-35 subunits directly ex vivo, CD B cells also presented reduced capacity for further IL-35 production upon activation.

Mannose-capped lipoarabinomannan-induced B10 cells decrease severity of dextran sodium sulphate-induced inflammatory bowel disease in mice

Inflammatory bowel disease (IBD) is a chronic, non‐specific, inflammatory gastrointestinal disease that mainly consists of Crohn's disease and ulcerative colitis. However, the aetiology and pathogenesis of IBD are still unclear. B10 (IL‐10 producing regulatory B) cells, a subset of regulatory B cells, are known to contribute to intestinal homeostasis and the aberrant frequency of B10 cells is associated with IBD. We have recently reported that B10 cells can be induced by ManLAM (mannose‐capped lipoarabinomannan), a major cell‐wall lipoglycan of M tb (Mycobacterium tuberculosis). In the current study, the ManLAM‐induced B10 cells were adoptively transferred into IL(interleukin)‐10^−/− mice and the roles of ManLAM‐induced B10 cells were investigated in DSS (dextran sodium sulphate)‐induced IBD model. ManLAM‐induced B10 cells decrease colitis severity in the mice. The B10 cells downregulate Th1 polarization in spleen and MLNs (mesenteric lymph nodes) of DSS‐treated mice. These results suggest that IL‐10 production by ManLAM‐treated B cells contributes to keeping the balance between CD4⁺ T cell subsets and protect mice from DSS‐induced IBD.

Phosphoinositide 3-Kinase P110δ-Signaling Is Critical for Microbiota-Activated IL-10 Production by B Cells that Regulate Intestinal Inflammation

The phosphoinositide 3-kinase catalytic subunit p110δ (PI3Kδ) gene maps to a human inflammatory bowel diseases (IBD) susceptibility locus, and genetic deletion of PI3Kδ signaling causes spontaneous colitis in mice. However, little is known regarding the role of PI3Kδ on IL-10-producing B cells that help regulate mucosal inflammation in IBD. We investigated the role of PI3Kδ signaling in B cell production of IL-10, following stimulation by resident bacteria and B cell regulatory function against colitis. In vitro, B cells from PI3KδD910A/D910A mice or wild-type B cells treated with PI3K specific inhibitors secreted significantly less IL-10 with greater IL-12p40 following bacterial stimulation. These B cells failed to suppress inflammatory cytokines by co-cultured microbiota-activated macrophages or CD4+ T cells. In vivo, co-transferred wild-type B cells ameliorated T cell-mediated colitis, while PI3KδD910A/D910A B cells did not confer protection from mucosal inflammation. These results indicate that PI3Kδ-signaling mediates regulatory B cell immune differentiation when stimulated with resident microbiota or their components, and is critical for induction and regulatory function of IL-10-producing B cells in intestinal homeostasis and inflammation.

Potential role of regulatory B cells in immunological diseases

Regulatory B cells (Bregs) are immune-modulating cells that affect the immune system by producing cytokines or cellular interactions. These cells have immunomodulatory effects on the immune system by cytokine production. The abnormalities in Bregs could be involved in various disorders such as autoimmunity, chronic infectious disease, malignancies, allergies, and primary immunodeficiencies are immune-related scenarios. Ongoing investigation could disclose the biology and the exact phenotype of these cells and also the assigned mechanisms of action of each subset, as a result, potential therapeutic strategies for treating immune-related anomalies. In this review, we collect the findings of human and mouse Bregs and the therapeutic efforts to change the pathogenicity of these cells in diverse disease.

Human Mesenchymal Stem Cell-Treated Regulatory CD23+CD43+ B Cells Alleviate Intestinal Inflammation

Rationale: Mesenchymal stem cells (MSCs) have been demonstrated to ameliorate inflammatory bowel disease by their actions on multiple immune cells, especially on regulatory B cells (Breg cells). However, the phenotypes and functions of human MSCs (hMSCs)-treated Breg cell subsets are not yet clear.

Methods: Purified B cells were cocultured with MSCs and the phenotypes and immunomodulatory functions of the B cells were analyzed by FACS and proliferation assays in vitro. Also, a trinitrobenzenesulfonic acid-induced mouse colitis model was employed to detect the function of MSC-treated Breg cells in vivo.

Results: We demonstrated that coculturing with hMSCs significantly enhanced the immunomodulatory activity of B cells by up-regulating IL-10 expression. We then identified that a novel regulatory B cell population characterized by CD23 and CD43 phenotypic markers could be induced by hMSCs. The CD23⁺CD43⁺ Breg cells substantially inhibited the inflammatory cytokine secretion and proliferation of T cells through an IL-10-dependent pathway. More significantly, intraperitoneal injection of hMSCs ameliorated the clinical and histopathological severity in the mouse experimental colitis model, accompanied by an increase in the number of CD23⁺CD43⁺ Breg cells. The adoptive transfer of CD23⁺CD43⁺ B cells effectively alleviated murine colitis, as compared with the CD23^-CD43^- B cells. Treatment with CD23⁺CD43⁺ B cells, and not hMSCs, substantially improved the symptoms of colitis in B cell-depleted mice.

Conclusion: the novel CD23⁺CD43⁺ Breg cell subset appears to be involved in the immunomodulatory function of hMSCs and sheds new light on elucidating the therapeutic mechanism of hMSCs for the treatment of inflammation-related diseases.

IL-33 Protects Mice against DSS-Induced Chronic Colitis by Increasing Both Regulatory B Cell and Regulatory T Cell Responses as Well as Decreasing Th17 Cell Response

BACKGROUND

Previously, we have reported that IL-33 functioned as a protective modulator in dextran sulfate sodium- (DSS-) induced chronic colitis by suppressing Th17 cell response in colon lamina propria and IL-33 induced both regulatory B cells (Bregs) and regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) of mice with DSS-induced acute colitis. Moreover, we speculated that IL-33 would promote the Treg or Breg responses leading to the attenuation of DSS-induced chronic colitis. So, we investigated the role of IL-33 on Bregs and Tregs in the MLN of DSS-induced chronic colitis mice.

METHODS

IL-33 was administered by intraperitoneal injection to mice with DSS-induced chronic colitis. Clinical symptoms, colon length, and histological changes were determined. The production of cytokines was measured by ELISA. The T and B cell subsets were measured by flow cytometry. The expression of mRNA of transcription factors was measured by quantitative real-time PCR.

RESULTS

We show that IL-33 treatment increases both Breg and Treg responses in the MLN of mice with DSS-induced chronic colitis. Moreover, IL-33 treatment also decreases Th17 cell response in the MLN of mice with DSS-induced chronic colitis.

CONCLUSION

Our data provide clear evidence that IL-33 plays a protective role in DSS-induced chronic colitis, which is closely related to increasing Breg and Treg responses in the MLN of mice as well as suppressing Th17 cell responses.

Glucocorticoid-Induced Leucine Zipper Inhibits Interferon-Gamma Production in B Cells and Suppresses Colitis in Mice

Glucocorticoid-induced leucine zipper (GILZ) is transcriptionally upregulated by glucocorticoids (GCs) and mediates many of the anti-inflammatory effects of GCs. Since B cell activity has been linked to cytokine production and modulation of inflammatory responses, we herein investigated the role of GILZ in B cells during colitis development. B cell-specific gilz knock-out (gilz B cKO) mice exhibited increased production of the pro-inflammatory cytokine IFN-γ in B cells, and consequently CD4⁺ T cell activation. Increased IFN-γ production in B cells was associated with enhanced transcriptional activity of the transcription factor activator protein-1 (AP-1) on the IFN-γ promoter. Moreover, GILZ deficiency in B cells was linked to enhanced susceptibility to experimental colitis in mice, and this was reversed by administering GILZ protein. Interestingly, we observed increased production of IFN-γ in both B and T cells infiltrating the lamina propria (LP) of gilz B cKO mice. Together, these findings indicate that GILZ controls IFN-γ production in B cells, which also affects T cell activity, and increased production of IFN-γ by B and T cells in LP is associated with predisposition to inflammatory colitis in mice.

Regulation of Intestinal Epithelial Cells Properties and Functions by Amino Acids

Intestinal epithelial cells (IECs) line the surface of intestinal epithelium, where they play important roles in the digestion of food, absorption of nutrients, and protection of the human body from microbial infections, and others. Dysfunction of IECs can cause diseases. The development, maintenance, and functions of IECs are strongly influenced by external nutrition, such as amino acids. Amino acids play important roles in regulating the properties and functions of IECs. In this article, we briefly reviewed the current understanding of the roles of amino acids in the regulation of IECs' properties and functions in physiological state, including in IECs homeostasis (differentiation, proliferation, and renewal), in intestinal epithelial barrier structure and functions, and in immune responses. We also summarized some important findings on the effects of amino acids supplementation (e.g., glutamine and arginine) in restoring IECs' and intestine functions in some diseased states. These findings will further our understanding of the important roles of amino acids in the homeostasis of IECs and could potentially help identify novel targets and reagents for the therapeutic interventions of diseases associated with dysfunctional IECs.

Old and New Lymphocyte Players in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, is a chronic intestinal inflammatory disorder characterized by diffuse accumulation of lymphocytes in the gut mucosa as a consequence of over-expression of endothelial adhesion molecules. The infiltrating lymphocytes have been identified as subsets of T cells, including T helper (Th)1 cells, Th17 cells, and regulatory T cells. The function of these lymphocyte subpopulations in the development of IBD is well-known, since they produce a number of pro-inflammatory cytokines, such as interferon-γ and interleukin-17A, which in turn activate mucosal proteases, thus leading to the development of intestinal lesions, i.e., ulcers, fistulas, abscesses, and strictures. However, the immune mechanisms underlying IBD are not yet fully understood, and knowledge about the function of newly discovered lymphocytes, including Th9 cells, innate lymphoid cells, mucosal-associated invariant T cells, and natural killer T cells, might add new pieces to the complex puzzle of IBD pathogenesis. This review summarizes the recent advances in the understanding of the role of mucosal lymphocytes in chronic intestinal inflammation and deals with the therapeutic potential of lymphocyte-targeting drugs in IBD patients.

Expression of Antisense Long Noncoding RNAs as Potential Regulators in Rainbow Trout with Different Tolerance to Plant-Based Diets

Reformulation of aquafeeds in salmonid diets to include more plant proteins is critical for sustainable aquaculture. However, increasing plant proteins can lead to stunted growth and enteritis. Toward an understanding of the regulatory mechanisms behind plant protein utilization, directional RNA sequencing of liver tissues from a rainbow trout strain selected for growth on an all plant-protein diet and a control strain, both fed a plant diet for 12 weeks, were utilized to construct long noncoding RNAs. Antisense long noncoding RNAs were selected for differential expression and functional analyses since they have been shown to have regulatory actions within a genome. A total of 142 unique antisense long noncoding RNAs were differentially expressed between strains, 60 of which could be mapped to a gene. Genes underlying these noncoding RNAs are indicated in lipid metabolism and immunity. Six noncoding transcripts were also found to overlap with differentially expressed protein-coding genes, all of which were co-expressed. Associating variation in regulatory elements between rainbow trout strains with differing tolerance to plant-protein diets will assist in future studies toward increased gains throughout carnivorous aquaculture.

miR-155 Regulates IL-10-Producing CD24hiCD27+ B Cells and Impairs Their Function in Patients with Crohn's Disease

Regulatory interleukin-10 (IL-10)-producing B cells (B10 cells) play a critical role in preventing and curing autoimmune diseases in experimental mouse models. However, the precise cellular and molecular mechanisms of action of B10 cells in humans, especially in patients with Crohn's disease (CD), remain to be determined. miR-155 regulates many physiological and pathological conditions, including inflammation such as that in CD. In this study, we aimed to explore the effect of miRNA-155 on IL-10 production by B cells in healthy controls (HCs) and CD patients. Interestingly, we found that CD24^hiCD27⁺ B cells express high levels of miRNA-155 and IL-10, which are positively correlated. Additionally, CD24^hiCD27⁺ B cells express higher levels of Toll-like receptor 9 than those found in other B cell subsets. Overexpression of miRNA-155 promotes IL-10 production, while inhibition of miRNA-155 decreases IL-10 production. We determined that miR-155 directly inhibits the expression of Jarid2, which reduces H3K27me3 binding to the IL10 promoter and increases IL-10 gene expression. In coculture systems, the CD24^hiCD27⁺ B cells from HCs suppressed the secretion of TNFα and IFNγ by monocytes and T cells, respectively. However, the number and function of CD24^hiCD27⁺ B cells from CD patients were decreased. Moreover, we found that miR-155 induces CD24^hiCD27⁺ B cells to produce higher levels of TNFα instead of IL-10 in CD patients than in the controls and that the increased number of IL-10⁺TNFα⁺ B cells reduces the induction of Foxp3 expression and the inhibition of IFNγ production by CD4⁺CD25^- T cells, as well as TNFα production by monocytes. Our study demonstrates the critical role of miRNA-155 in the regulation of IL-10 production by B cells and reveals the novel molecular mechanism underlying the functional impairment of B10 cells in CD patients. Our study has the potential to drive the development of B10 cell-based strategies to ameliorate disease progression in CD patients.

Human regulatory B cells in health and disease: therapeutic potential

Regulatory B cells (Bregs) modulate immune responses predominantly, although not exclusively, via the release of IL-10. The importance of human Bregs in the maintenance of immune homeostasis comes from a variety of immune-related pathologies, such as autoimmune diseases, cancers, and chronic infections that are often associated with abnormalities in Breg numbers or function. A continuous effort toward understanding Breg biology in healthy individuals will provide new opportunities to develop Breg immunotherapy that could prove beneficial in treating various immune-mediated pathologies. In this Review, we discuss findings regarding human Bregs, including their mechanisms of suppression and role in different disease settings. We also propose several therapeutic strategies targeting Bregs for better management of immune disorders.

A higher frequency of IL-10-producing B cells in Hepatitis B virus-associated membranous nephropathy

The purpose of this study is to elucidate the potential role of interleukin (IL)-10(+) regulatory B cells and other B cell subsets in the development of hepatitis B virus-associated membranous nephropathy (HBV-MN). A total of 14 patients with new onset HBV-MN, 12 individuals with immune-tolerant HBV infection (HBV-IT), and 12 healthy controls (HC) were examined for the percentages of CD38(+) , CD86(+) , CD27(+) , CD95(+) and IL-10(+) B cells by flow cytometry. Serum IL-10 concentration was examined by enzyme-linked immunosorbent assay (ELISA). The percentages of CD38(+) CD19(+) , CD86(+) CD19(+) , CD38(+) CD86(+) CD19(+) , and CD95(+) CD19(+) B cells were significantly higher in HBV-MN patients than the HBV-IT and HC. The percentages of CD5(+) CD19(+) , IL-10(+) CD19(+) B cells and serum IL-10 level in HBV-MN patients were significantly higher than the HC, and lower than the HBV-IT. Percentages of CD38(+) CD19(+) , and CD86(+) CD19(+) B cells were reduced after treatment, while the percentages of CD5(+) CD1d(+) CD19(+) , CD5(+) CD1d(+) IL-10(+) CD19(+) , and IL-10(+) CD19(+) B cells were increased. The 24 h urinary protein concentration was positively correlated with the percentage of CD38(+) CD19(+) , and negatively correlated with the percentage of IL-10(+) CD19(+) B cells and serum IL-10 level. Similarly, the value of eGFR was negatively correlated with the percentage of CD38(+) CD19(+) , and positively correlated with the percentage of IL-10(+) CD19(+) B cells and serum IL-10 level. Serum IL-10 level and the percentage of IL-10(+) CD19(+) were negatively correlated with the percentages of CD38(+) CD19(+) , and CD86(+) CD19(+) B cells. These results suggest that CD86(+) CD19(+) , CD38(+) CD86(+) CD19(+) , CD95(+) CD19(+) , and especially CD38(+) CD19(+) and IL-10(+) CD19(+) cells may participate in the pathogenesis of HBV-MN.

Ulcerative Colitis Is Characterized by a Decrease in Regulatory B Cells

BACKGROUND AND AIMS

Ulcerative colitis (UC) is characterized by Th2-polarized, B cell responses. However, neither size, composition, nor activity of the Breg compartment in active UC has been evaluated.

METHODS

Peripheral blood of 25 patients with UC, 5 patients with Crohn's disease (CD) and 15 control subjects was examined for Bregs subsets by flow cytometry. Intestinal tissue of 5 patients with UC, 3 patients with CD and 5 control subjects was also examined for Bregs. The levels of serum interleukin (IL)-10, immunoglobulin (Ig), and C-reactive protein (CRP), and the erythrocyte sedimentation rate (ESR) in individual subjects were measured. Interleukin-10 production in B cells isolated from patients with UC was examined. Potential associations between the values of the different measures were analysed by the Spearman correlation test.

RESULTS

Compared with controls, the UC patients had significantly reduced frequencies of CD24(high)CD38(high) and CD5(+) Bregs in peripheral blood as well as in intestinal tissues, accompanied by lower serum IL-10 levels. Interleukin-10 production was significantly decreased in stimulated B cells from patients with UC, whereas patient IL-10(+) B cells were found to be enriched in CD24(high)CD38(high) and CD5(+) B cells. However, increased percentages of CD95(+)-exhausted Bregs were encountered in subsets. Furthermore, Mayo clinic scores, CRP, and ESR in UC patients was negatively correlated with the frequency of Bregs and the IL-10 concentration, whereas these parameters were positively correlated with the frequency of CD95(+)-exhausted Bregs and the IgG levels.

CONCLUSIONS

Active UC is characterized by exhaustion of regulatory control in the B cell compartment.

Cytokine-producing B cells: a translational view on their roles in human and mouse autoimmune diseases

B-cell depletion therapy has beneficial effects in autoimmune diseases. This is only partly explained by an elimination of autoantibodies. How does B-cell depletion improve disease? Here, we review preclinical studies showing that B cells can propagate autoimmune disorders through cytokine production. We also highlight clinical observations indicating the relevance of these B-cell functions in human autoimmunity. Abnormalities in B-cell cytokine production have been observed in rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, and systemic lupus erythematosus. In the first two diseases, B-cell depletion erases these abnormalities, and improves disease progression, suggesting a causative role for defective B-cell cytokine expression in disease pathogenesis. However, in the last two disorders, the pathogenic role of B cells and the effect of B-cell depletion on cytokine-producing B cells remain to be clarified. A better characterization of cytokine-expressing human B-cell subsets, and their modulation by B cell-targeted therapies might help understanding both the successes and failures of current B cell-targeted approaches. This may even lead to the development of novel strategies to deplete or amplify selectively pathogenic or protective subsets, respectively, which might be more effective than global depletion of the B-cell compartment.

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.

Downregulation of serotonin reuptake transporter gene expression in healing colonic mucosa in presence of remaining low-grade inflammation in ulcerative colitis

BACKGROUND AND AIM

The serotonin reuptake transporter (SERT) terminates serotonin activity by removing it from interstitial space. Downregulated colonic SERT expression has been reported in irritable bowel disease (IBS), and symptoms resembling IBS occur in cases of inflammatory bowel disease (IBD) in remission; thus, a common pathogenesis for IBS and IBD is possible. However, little is known regarding SERT expression in colonic mucosa of IBD patients during healing.

METHODS

Twenty-two ulcerative colitis (UC) patients underwent colonoscopy examinations, during which inflamed mucosa was distinguished from that undergoing healing. Healing mucosa was classified into regular and irregular vessel patterns by narrowband imaging magnifying colonoscopy. Expressions of SERT and various inflammation-related genes in biopsy samples were assessed using a polymerase chain reaction array system and real-time polymerase chain reaction. Colitis model mice were established by administration of dextran sodium sulfate or transfer of CD4(+) T cells isolated from SAMP1 mice, then time-course changes of SERT and inflammatory gene expressions were observed in colonic mucosa.

RESULTS

In UC patients, SERT expression in inflamed mucosa was significantly lower than in healing mucosa. SERT expression was decreased in healing mucosa with an irregular vessel pattern with mildly increased levels of inflammatory gene expression. In mice, SERT expression was suppressed in inflamed mucosa and continuously observed with low-grade mucosal inflammation during colitis healing.

CONCLUSIONS

Sserotonin reuptake transporter expression is downregulated in healing colonic mucosa of UC patients and that suppression may be dependent on the presence of remaining low-grade colonic inflammation.

Beneficial Effects of Fecal Microbiota Transplantation on Ulcerative Colitis in Mice

BACKGROUND

Ulcerative colitis (UC) is a chronic condition and the most common form of inflammatory bowel disease. The goal of standard treatment is mainly to induce and maintain remission with anti-inflammatory, immunosuppressive agents, and/or colectomy. Fecal microbiota transplantation (FMT) has been used successfully to treat relapsing or refractory Clostridium difficile infection. The alteration of microbiota in mouse models of UC as well as in patients suggested the possibility of treating UC with FMT.

AIMS

To study the effects of FMT on dextran sodium sulfate (DSS)-induced UC model in mice.

METHODS

Littermates of BALB/c and C57BL/6J were randomized into four groups: normal control , treatment with DSS for 7 days (DSS - FMT), treatment with DSS followed by FMT for another 8 days (DSS + FMT), and treatment with DSS and FMT followed by another 5 days for recovery (remission). Body weight, survival rate, and DAI scores of mice in each group were recorded. Changes in distal colon were studied by histopathology. Alterations of spleen and lamina propria regulatory lymphocytes, major bacterial species in feces and inflammatory cytokines in colon were also studied.

RESULTS

C57BL/6J mice experienced more significant weight loss than BALB/c mice after DSS treatment, regardless of whether the two strains of mice were co-housed or not. FMT caused reversal of DAI scores in BALB/c but not in C57BL/6J mice. In BALB/c mice, FMT also reduced colon inflammation that was paralleled by decreased inflammatory cytokine levels, altered bacterial microbiota, and regulatory lymphocyte proportions.

CONCLUSIONS

FMT is effective in a mouse model of UC through its modulation on gut microbiota and the host immune system.

Oral tolerance is inducible during active dextran sulfate sodium-induced colitis

AIM: To investigate whether oral tolerance is inducible during the active phase of dextran sulfate sodium (DSS)-induced colitis.

METHODS: Colitis was induced in 6- to 8-wk-old female BALB/c mice by the administration of 2% DSS. To induce oral tolerance, mice that received water with DSS [DSS (+)] and mice that received autoclaved water [DSS (-)] were intragastrically (i.g.) administered ovalbumin (OVA) as a tolerogen before systemic challenge with OVA. Following this, serum levels of OVA-specific IgE antibodies were measured. In mice with active colitis, CD4⁺CD25⁺Foxp3⁺ cell and B10 cell frequencies were evaluated using flow cytometry. Cytokine mRNA expression profiles were evaluated by reverse transcription real-time polymerase chain reaction.

RESULTS: Regardless of the presence of DSS colitis, OVA-specific immunoglobulin E concentrations were significantly reduced in mice that were i.g. administered OVA compared to mice that were i.g. administered PBS [DSS (+): 4.4 (4.2-9.5) ng/mL vs 83.9 (66.1-123.2) ng/mL, P < 0.01; DSS (-): 27.7 (0.1-54.5) ng/mL vs 116.5 (80.6-213.6) ng/mL, P < 0.01]. These results demonstrated that oral tolerance was induced in both the presence and absence of colitis. In the spleen and mesenteric lymph nodes (MLN), the frequencies of CD4⁺CD25⁺Foxp3⁺ cells and B10 cells, both of which are associated with oral tolerance, did not significantly change. In the spleen, interferon-γ mRNA expression significantly decreased in mice with colitis [DSS (+): 0.42 (0.31-0.53) vs DSS (-): 1.00 (0.84-1.39), P < 0.01]. The expression levels of other cytokines did not significantly change.

CONCLUSION: Oral tolerance is inducible during active DSS colitis. The stability of regulatory cell populations in the spleen and MLN in colitis might correlate with these results.

Decreased Frequency of Intestinal Regulatory CD5+ B Cells in Colonic Inflammation

Background

CD5⁺ B cells are a type of regulatory immune cells, though the involvement of this B cell subset in intestinal inflammation and immune regulation is not fully understood.

Methods

We examined the distribution of CD5⁺ B cells in various mouse organs. Expression levels of CD11b, IgM, and toll-like receptor (TLR)-4 and -9 in B cells were evaluated. In vitro, TLR-stimulated IL-10 production by colonic lamina propria (LP) CD5⁺ and CD5^- B cells was measured. In vivo, mice with acute or chronic dextran sulfate sodium (DSS)-induced colonic injury were examined, and the frequency of colonic LP CD5⁺ B cells in those was assessed by flow cytometry.

Results

The expression level of TLR9 was higher in colonic LP CD5⁺ B cells as compared to CD5^- B cells. Colonic LP CD5⁺ B cells produced greater amounts of IL-10 following stimulation with TLR ligands, especially TLR9, as compared with the LP CD5^- B cells. Acute intestinal inflammation transiently decreased the frequency of colonic LP CD5⁺ B cells, while chronic inflammation induced a persistent decrease in colonic LP CD5⁺ B cells and led to a CD5^- B cell-dominant condition.

Conclusion

A persistent altered mucosal B cell population caused by chronic gut inflammation may be involved in the pathogenesis of inflammatory bowel diseases.

Regulatory immune cells in regulation of intestinal inflammatory response to microbiota

The intestinal lumen harbors nearly 100 trillion commensal bacteria that exert crucial function for health. An elaborate balance between immune responses and tolerance to intestinal microbiota is required to maintain intestinal homeostasis. This process depends on diverse regulatory mechanisms, including both innate and adaptive immunity. Dysregulation of the homeostasis between intestinal immune systems and microbiota has been shown to be associated with the development of inflammatory bowel diseases (IBD) in genetically susceptible populations. In this review, we discuss the recent progress reported in studies of distinct types of regulatory immune cells in the gut, including intestinal intraepithelial lymphocytes, Foxp3(+) regulatory T cells, regulatory B cells, alternatively activated macrophages, dendritic cells, and innate lymphoid cells, and how dysfunction of this immune regulatory system contributes to intestinal diseases such as IBD. Moreover, we discuss the manipulation of these regulatory immune cells as a potential therapeutic method for management of intestinal inflammatory disorders.

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.

Peripheral CD5+ B cells in antineutrophil cytoplasmic antibody-associated vasculitis

OBJECTIVE

CD5+ B cells have been conceptualized as a possible surrogate for Breg cells. The aim of the present study was to determine the utility of CD5+ B cells as biomarkers in antineutrophil cytoplasmic antibody-associated vasculitis (AAV).

METHODS

The absolute and relative numbers (percentages) of CD5+ B cells (explanatory variables) were measured longitudinally during 18 months in 197 patients randomized to receive either rituximab (RTX) or cyclophosphamide (CYC) followed by azathioprine (AZA) for the treatment of AAV (Rituximab in ANCA-Associated Vasculitis [RAVE] trial). Outcome variables included disease activity (status of active disease versus complete remission), responsiveness to induction therapy, disease relapse, disease severity, and, in RTX-treated patients, relapse-free survival according to the percentage of CD5+ B cells detected upon B cell repopulation.

RESULTS

CD5+ B cell numbers were comparable between the treatment groups at baseline. After an initial decline, absolute CD5+ B cell numbers progressively increased in patients in the RTX treatment arm, but remained low in CYC/AZA-treated patients. In both groups, the percentage of CD5+ B cells increased during remission induction and slowly declined thereafter. During relapse, the percentage of CD5+ B cells correlated inversely with disease activity in RTX-treated patients, but not in patients who received CYC/AZA. No significant association was observed between the numbers of CD5+ B cells and induction treatment failure or disease severity. The dynamics of the CD5+ B cell compartment did not anticipate disease relapse. Following B cell repopulation, the percentage of CD5+ B cells was not predictive of time to flare in RTX-treated patients.

CONCLUSION

The percentage of peripheral CD5+ B cells might reflect disease activity in RTX-treated patients. However, sole staining for CD5 as a putative surrogate marker for Breg cells did not identify a subpopulation of B cells with clear potential for meaningful clinical use. Adequate phenotyping of Breg cells is required to further explore the value of these cells as biomarkers in AAV.

Apoptotic cells ameliorate chronic intestinal inflammation by enhancing regulatory B-cell function

Apoptosis is a programmed physiological death of unwanted cells, and handling of apoptotic cells (ACs) is thought to have profound effects on immune-mediated disorders. However, there is scant information regarding the role of ACs in intestinal inflammation, in which immune homeostasis is a major concern. To investigate this, we injected ACs into a severe combined immunodeficiency adoptive transfer model of chronic colitis in the presence and absence of cotransferred whole B or regulatory B cell (Breg)-depleted B cells. We also injected syngeneic ACs into AKR/N mice as a control and into milk fat globule-epidermal growth factor 8 knockout mice deficient of phagocytic function. Chronic colitis severity was significantly reduced in the AC as opposed to the phosphate-buffered saline group with cotransferred whole B cells. The AC-mediated effect was lost in the absence of B cells or presence of Breg-depleted B cells. In addition, ACs induced splenic B cells to secrete significantly increased levels of interleukin 10 in AKR/N mice but not milk fat globule-epidermal growth factor 8 knockout mice. Apoptotic leukocytes were induced by reactive oxygen species during granulocyte/monocyte apheresis therapy in rabbits and H2O2-induced apoptotic neutrophils ameliorated mice colitis. Our results indicate that ACs are protective only in the presence of B cells and phagocytosis of ACs induced interleukin 10 producing Bregs. Thus, the ameliorative effect seen in this study might have been exerted by AC-induced Bregs through increased production of the immunosuppressive cytokine interleukin 10, whereas an AC-mediated effect may contribute to the anti-inflammatory effect of granulocyte/monocyte apheresis as a novel therapeutic mechanism for inflammatory bowel disease.

Dynamic analysis of tumor-associated immune cells in DEN-induced rat hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an aggressive disease with poor prognosis and limited methods to predict patient survival. Immune cells infiltrating tumors are known to impact tumor progression. Here, we analyzed the phenotype and function of dendritic cells (DCs), and the frequency of IL-10-producing regulatory B cells (Breg) and Foxp3(+) regulatory T cells (Treg) in different stages of N-nitrosodiethylamine (DEN)-induced rat HCC in order to understand their roles in this disease. 4weeks following DEN treatment, no significant differences in CD80 and CD86 expression were found on DCs from HCC rats and normal rats but 12 and 16weeks following DEN treatment, the expression of CD80, CD86 and MHCII on DCs of HCC rats was significantly decreased. We also found that the frequency of IL-10-producing Breg and CD4(+)CD25(+)Foxp3(+) Treg in HCC rats was obviously increased during all of these three stages. In addition, the bone-marrow derived DCs (BMDCs) from HCC rats displayed lower ability in activating T cells and an increase in IL-10 secretion. No differences in IL-12 level and endocytosis ability were found on BMDCs from HCC rats and normal rats. Our results suggest that the dysfunction of DCs and the increase of IL-10-producing Breg and Foxp3(+) Treg might play important roles in HCC progression.