Characterisation of allergen-specific responses of IL-10-producing regulatory B cells (Br1) in Cow Milk Allergy

The pathogenesis of food allergy and protection offered by dietary compounds from the perspective of epigenetics

Food allergy is a global food safety concern, with an increasing prevalence in recent decades. However, the immunological and cellular mechanisms involved in allergic reactions remain incompletely understood, which impedes the development of effective prevention and treatment strategies. Current evidence supports those epigenetic modifications regulate the activation of immune cells, and their dysregulation can contribute to the development of food allergies. Patients with food allergy show epigenetic alterations that lead to the onset, duration and recovery of allergic disease. Moreover, many preclinical studies have shown that certain dietary components exert nutriepigenetic effects in changing the course of food allergies. In this review, we provide an up-to-date overview of DNA methylation, noncoding RNA and histone modification, with a focus on their connections to food allergies. Following this, we discuss the epigenetic mechanisms that regulate the activation and differentiation of innate and adapted immune cell in the context of food allergies. Subsequently, this study specifically focuses on the multidimensional epigenetic effects of dietary components in modulating the immune response, which holds promise for preventing food allergies in the future.

Regulatory B Cells-Immunopathological and Prognostic Potential in Humans

The aim of the following review is to shed light on the putative role of regulatory B cells (Bregs) in various human diseases and highlight their potential prognostic and therapeutic relevance in humans. Regulatory B cells are a heterogeneous group of B lymphocytes capable of suppressing inflammatory immune reactions. In this way, Bregs contribute to the maintenance of tolerance and immune homeostasis by limiting ongoing immune reactions temporally and spatially. Bregs play an important role in attenuating pathological inflammatory reactions that can be associated with transplant rejection, graft-versus-host disease, autoimmune diseases and allergies but also with infectious, neoplastic and metabolic diseases. Early studies of Bregs identified IL-10 as an important functional molecule, so the IL-10-secreting murine B10 cell is still considered a prototype Breg, and IL-10 has long been central to the search for human Breg equivalents. However, over the past two decades, other molecules that may contribute to the immunosuppressive function of Bregs have been discovered, some of which are only present in human Bregs. This expanded arsenal includes several anti-inflammatory cytokines, such as IL-35 and TGF-β, but also enzymes such as CD39/CD73, granzyme B and IDO as well as cell surface proteins including PD-L1, CD1d and CD25. In summary, the present review illustrates in a concise and comprehensive manner that although human Bregs share common functional immunosuppressive features leading to a prominent role in various human immunpathologies, they are composed of a pool of different B cell types with rather heterogeneous phenotypic and transcriptional properties.

The role of regulatory B cells in immune regulation and childhood allergic asthma

BACKGROUND

As the most common chronic disease in childhood, asthma displays a major public health problem worldwide with the incidence of those affected rising. As there is currently no cure for allergic asthma, it is mandatory to get a better understanding of the underlying molecular mechanism.

MAIN BODY

By producing IgE antibodies upon allergen contact, B cells play a pivotal role in allergic asthma. Besides that, IL-10-secreting B cell subsets, namely regulatory B cells (Bregs), are reported in mice and humans to play a role in allergic asthma. In humans, several Breg subsets with distinct phenotypic and functional properties are identified among B cells at different maturational and differentiation stages that exert anti-inflammatory functions by expressing several suppressor molecules. Emerging research has focused on the role of Bregs in allergic asthma as well as their role for future diagnostic and preventive strategies.

CONCLUSION

Knowledge about the exact function of human Bregs in allergic asthma is still very limited. This review aims to summarize the current knowledge on Bregs. We discuss different human Breg subsets, several ways of Breg induction as well as the mechanisms through which they exert immunoregulatory functions, and their role in (childhood) allergic asthma.

The dichotomy of regulatory B cells in cancer versus allergic disease

Regulatory B cells (Bregs) are an immunosuppressive cell phenotype that affects the immune system by limiting the inflammatory cascade. Dysregulation of Bregs can interestingly play a dichotomous role in the pathophysiology of many diseases and is especially highlighted when examining cancer pathology compared to allergic disease. This study reviews the existing literature on Bregs and compares their role in allergic disease in contrast to cancer development. Upregulation of Bregs in cancer states has been associated with poor prognostic outcomes across various cancer types, and Breg proliferation was associated with chronic interferon signaling, activation of the BCR-BTK (B cell receptor-Bruton's tyrosine kinase) pathway, and release of C-X-C motif ligand 13. In contrast, Breg dysfunction has been identified as a key mechanism in many allergic diseases, such as allergic asthma, allergic rhinitis, atopic dermatitis, and contact dermatitis. Development of Breg-targeted immunotherapies is currently at the preclinical level, but strategies differentially focus on Breg depletion in cancer versus Breg stimulation in allergy. Our review highlights the divergent functions that Bregs play in cancer compared to allergy. We conclude that natural homeostasis hinges on a fine balance between the dichotomous role of Bregs-over or underactivation can result in a pathological state.

B cells: The many facets of B cells in allergic diseases

B cells play a key role in our immune system through their ability to produce antibodies, suppress a proinflammatory state, and contribute to central immune tolerance. We aim to provide an in-depth knowledge of the molecular biology of B cells, including their origin, developmental process, types and subsets, and functions. In allergic diseases, B cells are well known to induce and maintain immune tolerance through the production of suppressor cytokines such as IL-10. Similarly, B cells protect against viral infections such as severe acute respiratory syndrome coronavirus 2 that caused the recent coronavirus disease 2019 pandemic. Considering the unique and multifaceted functions of B cells, we hereby provide a comprehensive overview of the current knowledge of B-cell biology and its clinical applications in allergic diseases, organ transplantation, and cancer.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease’s origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a “double-edged sword” in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

IL-10-producing memory B regulatory cells as a novel target for HLA-G to prolong human kidney allograft survival

Despite the growing interest in the role of regulatory B cells (Bregs) in autoimmunity, their distinct role and function in kidney transplant outcomes remain elusive. Here, we retrospectively analyzed the proportion of Bregs, transitional Bregs (tBregs) and memory Bregs (mBregs) and their capacity to produce IL-10 in non-rejected (NR) versus rejected (RJ) kidney transplant recipients. In the NR group, we observed a significant increase in the proportion of mBregs (CD19⁺CD24^hiCD27⁺) but no difference in tBregs (CD19⁺CD24^hiCD38⁺), as compared to the RJ group. We also observed a significant increase in IL-10-producing mBregs (CD19⁺CD24^hiCD27⁺IL-10⁺) in the NR group. As our group and others have previously reported a potential role of the human leukocyte antigen G (HLA-G) in human renal allograft survival, notably through IL-10, we then investigated possible crosstalk between HLA-G and IL-10⁺ mBregs. Our ex vivo data suggest a role of HLA-G in enhancing IL-10⁺ mBreg expansion upon stimulation, which further decreased CD3⁺ T cell proliferation capability. Using RNA-sequencing (RNA-seq), we identified potential key signaling pathways involved in HLA-G-driven IL-10⁺ mBreg expansion, such as the MAPK, TNF and chemokine signaling pathways. Together, our study highlights a novel HLA-G-mediated IL-10-producing mBreg pathway that may serve as a therapeutic target to improve kidney allograft survival.

Alteration of the allergenicity of cow's milk proteins using different food processing modifications

Milk is an essential source of protein for infants and young children. At the same time, cow's milk is also one of the most common allergenic foods causing food allergies in children. Recently, cow's milk allergy (CMA) has become a common public health issue worldwide. Modern food processing technologies have been developed to reduce the allergenicity of milk proteins and improve the quality of life of patients with CMA. In this review, we summarize the main allergens in cow's milk, and introduce the recent findings on CMA responses. Moreover, the reduced effects and underlying mechanisms of different food processing techniques (such as heating, high pressure, γ-ray irradiation, ultrasound irradiation, hydrolysis, glycosylation, etc.) on the allergenicity of cow's milk proteins, and the application of processed cow's milk in clinical studies, are discussed. In addition, we describe the changes of nutritional value in cow's milk treated by different food processing technologies. This review provides an in-depth understanding of the allergenicity reduction of cow's milk proteins by various food processing techniques.

Leptin favors Th17/Treg cell subsets imbalance associated with allergic asthma severity

Background

Obesity has often been associated with severe allergic asthma (AA). Here, we analyzed the frequency of different circulating CD4⁺T‐cell subsets from lean, overweight and obese AA patients.

Methods

Mononuclear cells from peripheral blood were obtained from 60 AA patients and the frequency of different CD4⁺T‐cell subsets and type 1 regulatory B cells (Br1) was determined by cytometry. The effect of obese‐related leptin dose on cytokine production and Treg cell function in AA‐derived CD4⁺ T cell cultures was evaluated by ELISA and 3H thymidine uptake, respectively. Leptin levels were quantified in the plasma by ELISA. According to the BMI, patients were stratified as lean, overweight and obese.

Results

AA severity, mainly among obese patients, was associated with an expansion of hybrid Th2/Th17 and Th17‐like cells rather than classic Th2‐like cells. On the other hand, the frequencies of Th1‐like, Br1 cells and regulatory CD4⁺ T‐cell subsets were lower in patients with severe AA. While percentages of the hybrid Th2/Th17 phenotype and Th17‐like cells positively correlated with leptin levels, the frequencies of regulatory CD4⁺ T‐cell subsets and Br1 cells negatively correlated with this adipokine. Interestingly, the obesity‐related leptin dose not only elevated Th2 and Th17 cytokine levels, but also directly reduced the Treg function in CD4⁺ T cell cultures from lean AA patients.

Conclusion

In summary, our results indicated that obesity might increase AA severity by favoring the expansion of Th17‐like and Th2/Th17 cells and decreasing regulatory CD4⁺T cell subsets, being adverse effects probably mediated by leptin overproduction.

Autoimmunity and Cancer-Two Sides of the Same Coin

Autoimmune disease results from the immune response against self-antigens, while cancer develops when the immune system does not respond to malignant cells. Thus, for years, autoimmunity and cancer have been considered as two separate fields of research that do not have a lot in common. However, the discovery of immune checkpoints and the development of anti-cancer drugs targeting PD-1 (programmed cell death receptor 1) and CTLA-4 (cytotoxic T lymphocyte antigen 4) pathways proved that studying autoimmune diseases can be extremely helpful in the development of novel anti-cancer drugs. Therefore, autoimmunity and cancer seem to be just two sides of the same coin. In the current review, we broadly discuss how various regulatory cell populations, effector molecules, genetic predisposition, and environmental factors contribute to the loss of self-tolerance in autoimmunity or tolerance induction to cancer. With the current paper, we also aim to convince the readers that the pathways involved in cancer and autoimmune disease development consist of similar molecular players working in opposite directions. Therefore, a deep understanding of the two sides of immune tolerance is crucial for the proper designing of novel and selective immunotherapies.

Mesenchymal stem/stromal cell therapy in atopic dermatitis and chronic urticaria: immunological and clinical viewpoints

Allergic diseases are immune-mediated diseases. Allergies share a common immunopathogenesis, with specific differences according to the specific disease. Mesenchymal stem/stromal cells (MSCs) have been applied to people suffering from allergic and many other diseases. In this review, the immunologic roles of MSCs are systemically reviewed according to disease immunopathogenesis from a clinical viewpoint. MSCs seem to be a promising therapeutic modality not only as symptomatic treatments but also as causative and even preventive treatments for allergic diseases, including atopic dermatitis and chronic urticaria.

Regulatory B cells, A to Z

B cells play a central role in the immune system through the production of antibodies. During the past two decades, it has become increasingly clear that B cells also have the capacity to regulate immune responses through mechanisms that extend beyond antibody production. Several types of human and murine regulatory B cells have been reported that suppress inflammatory responses in autoimmune disease, allergy, infection, transplantation, and cancer. Key suppressive molecules associated with regulatory B-cell function include the cytokines IL-10, IL-35, and TGF-β as well as cell membrane-bound molecules such as programmed death-ligand 1, CD39, CD73, and aryl hydrocarbon receptor. Regulatory B cells can be induced by a range of different stimuli, including microbial products such as TLR4 or TLR9 ligands, inflammatory cytokines such as IL-6, IL-1β, and IFN-α, as well as CD40 ligation. This review provides an overview of our current knowledge on regulatory B cells. We discuss different types of regulatory B cells, the mechanisms through which they exert their regulatory functions, factors that lead to induction of regulatory B cells and their role in the alteration of inflammatory responses in different diseases.

B Cell Functions in the Development of Type I Allergy and Induction of Immune Tolerance

B cells are key players in the mechanisms underlying allergic sensitization, allergic reactions, and tolerance to allergens. Allergen-specific immune responses are initiated when peptide:MHCII complexes on dendritic cells are recognized by antigen-specific receptors on T cells followed by interactions between costimulatory molecules on the surfaces of B and T cells. In the presence of IL-4, such T-B cell interactions result in clonal expansion and isotype class-switching to IgE in B cells, which will further differentiate into either memory B cells or PCs. Allergic reactions are then triggered upon cross-linking of IgE-FcɛRI complexes on basophils and mast cells, leading to cell degranulation and the release of pro-inflammatory mediators.Mechanisms underlying effective allergen-specific immunotherapy (AIT) involve the induction of Tregs and the secretion of blocking IgG4 antibodies, which together mediate the onset and maintenance of immune tolerance towards non-hazardous environmental antigens. However, the importance of regulatory B cells (Breg) for tolerance induction during AIT has gained more attention lately. Studies in grass pollen- and house dust mite-allergic patients undergoing SCIT reported increased frequencies of IL-10+ Breg cells and a positive correlation between their number and the improvement of clinical symptoms. Thus, Breg are emerging as biomarkers for monitoring tolerance to allergens under natural exposure conditions and during AIT. Further research on the role of other anti-inflammatory cytokines secreted by Breg will help to understand their role in disease development and tolerance induction.

Regulatory and IgE+ B Cells in Allergic Asthma

Allergic asthma is triggered by inhalation of environmental allergens resulting in bronchial constriction and inflammation, which leads to clinical symptoms such as wheezing, coughing, and difficulty breathing. Asthmatic airway inflammation is initiated by inflammatory mediators released by granulocytic cells. However, the immunoglobulin E (IgE) antibody is necessary for the initiation of the allergic cascade, and IgE is produced and released exclusively by memory B cells and plasma cells. Acute allergen exposure has also been shown to increase IgE levels in the airways of patients diagnosed with allergic asthma; however, more studies are needed to understand local airway inflammation. Additionally, regulatory B cells (B_regs) have been shown to modulate IgE-mediated inflammatory processes in allergic asthma pathogenesis, particularly in mouse models of allergic airway disease. However, the levels and function of these IgE⁺ B cells and B_regs remain to be elucidated in human models of asthma. The overall objective for this chapter is to provide detailed methodological, and insightful technological advances to study the biology of B cells in allergic asthma pathogenesis. Specifically, we will describe how to investigate the frequency and function of IgE⁺ B cells and B_regs in allergic asthma, and the kinetics of these cells after allergen exposure in a human asthma model.

Use of Toll-Like Receptor (TLR) Ligation to Characterize Human Regulatory B-Cells Subsets

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs), which constitute key components in the recognition of pathogens, thereby initiating innate immune responses and promoting adaptive immune responses. In B cells, TLR ligation is important for their activation and, together with CD40, for their differentiation. TLR ligands are also strong promoters of regulatory B (Breg)-cell development, by enhancing the production of IL-10 and their capacity to induce tolerance. In inflammatory diseases, such as autoimmunity or allergies, Breg-cell function is often impaired, while in chronic infections, such as with helminths, or cancer, Breg-cell function is boosted. Following pathogen exposure, B cells can respond directly by producing cytokines and/or IgM (innate response) and develop into various memory B (Bmem)-cell subsets with class-switched immunoglobulin receptors. Depending on the disease state or chronic infection conditions, various Breg subsets can be recognized as well. Currently, a large array of surface markers is known to distinguish between these large range of B-cell subsets. In recent years, the development of mass cytometers and spectral flow cytometry has allowed for high-dimensional detection of up to 48 markers, including both surface and intracellular/intranuclear markers. Therefore, this novel technology is highly suitable to provide a comprehensive overview of Bmem/Breg-cell subsets in different disease states and/or in clinical intervention trials. Here, we provide detailed instructions of the steps necessary to obtain high-quality data for high-dimensional analysis of multiple human Breg-cell subsets using various TLR ligands.

B regulatory cells in allergy

B cells have classically been recognized for their unique and indispensable role in the production of antibodies. Their potential as immunoregulatory cells with anti-inflammatory functions has received increasing attention during the last two decades. Herein, we highlight pioneering studies in the field of regulatory B cell (Breg) research. We will review the literature on Bregs with a particular focus on their role in the regulation of allergic inflammation.

A pilot study towards the immunological effects of omalizumab treatment used to facilitate oral immunotherapy in peanut-allergic adolescents

Anti-IgE treatments, such as omalizumab, have shown promising effects in allergy treatment. Our previous work has shown that individualized omalizumab treatment (OT) allows a safe initiation and rapid up-dosing of peanut oral immunotherapy (OIT) in peanut-allergic adolescents. However, the broader immunological effects of this OT are incompletely understood. In this pilot study, we longitudinally followed the total B- and T-cell immunity during OT, using flow cytometry, ELISpot and ELISA. Peripheral blood mononuclear cells (PBMCs) and plasma were collected from participants (n = 17) at several timepoints during treatment, before starting OT (baseline), prior to starting OIT during OT (start OIT) and at maintenance dose OIT prior to OT reduction (maintenance). OT did not affect the total B-cell compartment over treatment time, but our results suggest an association between the OT dosage scheme and the B-cell compartment. Further, in vitro polyclonal T-cell activation at the different timepoints suggests a cytokine skewing towards the Th1 phenotype at the expense of Th2- and Th9-related cytokines during treatment. No differences in the frequencies or phenotype of regulatory T cells (Tregs) over treatment time were observed. Finally, plasma chemokine levels were stable over treatment time, but suggest elevated gut homing immune responses in treatment successes during the treatment as compared to treatment failures. The novel and explorative results of this pilot study help to improve our understanding on the immunological effects of OT used to facilitate OIT and provide guidance for future immunological investigation in large clinical trials.

Heterogeneous subsets of B-lineage regulatory cells (Breg cells)

B cells represent a key cellular component of humoral immunity. Besides antigen presentation and antibody production, B cells also play a role in immune regulation and induction of tolerance through several mechanisms. Our understanding of B-lineage cells with regulatory ability has been revolutionized by the delineation of heterogeneous subsets of these cells. Specific environmental signals may further determine the polarization and function of B-lineage regulatory cells. With the availability of new genetic, molecular and pharmacological tools, considerable advances have been made toward our understanding of the surface phenotype, developmental processes and functions of these cells. These exciting discoveries, some of which are still controversial, also raise many new questions, which makes the inhibitory function of B cells a rapidly growing field in immunopathology. Here we review highlights of the regulatory activity of B cells and the recent advances in the function and phenotype of these B-cell subsets in healthy and diseased states.

A Potential Role for Epigenetically Mediated Trained Immunity in Food Allergy

The prevalence of IgE-mediated food allergy is increasing at a rapid pace in many countries. The association of high food allergy rates with Westernized lifestyles suggests the role of gene-environment interactions, potentially underpinned by epigenetic variation, in mediating this process. Recent studies have implicated innate immune system dysfunction in the development and persistence of food allergy. These responses are characterized by increased circulating frequency of innate immune cells and heightened inflammatory responses to bacterial stimulation in food allergic patients. These signatures mirror those described in trained immunity, whereby innate immune cells retain a “memory” of earlier microbial encounters, thus influencing subsequent immune responses. Here, we propose that a robust multi-omics approach that integrates immunological, transcriptomic, and epigenomic datasets, combined with well-phenotyped and longitudinal food allergy cohorts, can inform the potential role of trained immunity in food allergy.

Lactobacillus Casei Zhang Alleviates Shrimp Tropomyosin-Induced Food Allergy by Switching Antibody Isotypes through the NF-κB-Dependent Immune Tolerance

SCOPE

Shellfish allergy is an important cause of food allergy, and tropomyosin (TM) is the major allergen within shellfish. Probiotics are safe bacteria that benefit host health and nutrition and is proposed as a novel approach for treating immunological diseases, including food allergies.

METHODS AND RESULTS

The probiotic strain Lactobacillus casei Zhang (LcZ) isolated from koumiss is investigated for its capacity to modulate food allergy induced by TM in BALB/c mice. Oral administration of LcZ attenuated allergy symptoms and intestinal epithelial damage. Furthermore, flow cytometry, real-time quantitative PCR, and ELISA demonstrated that LcZ administration altered the development and function of dendritic cells (DCs), T cells, and B cells, finally resulting in the change of TM-specific antibody isotypes into a tolerogenic pattern. Moreover, an in vitro spleen cell culture model reveals that LcZ directly modulates regulatory tolerogenic DC and T cell development, dependent on the activation of the nuclear factor kappa B (NF-κB) signaling pathway.

CONCLUSION

This work indicates the ability of LcZ to alleviate TM-induced food allergy and demonstrates the involvement of the tolerogenic immune cells and NF-κB signaling pathway, indicating LcZ to be a potential immunomodulator and immunotherapy assistor.

Regulatory B cells and transplantation: almost prime time?

PURPOSE OF REVIEW

Regulatory B cells (Bregs) are potent inhibitors of the immune system with the capacity to suppress autoimmune and alloimmune responses. Murine transplant models showing that Bregs can promote allograft tolerance are now supported by clinical data showing that patients who develop operational tolerance have higher frequency of Bregs. Breg function has been widely studied resulting in improved understanding of their biology and effector mechanisms. However, our overall understanding of Bregs remains poor due the lack of specific marker, limited knowledge of how and where they act in vivo, and whether different Breg subpopulations exhibit different functions.

RECENT FINDINGS

In this review we detail murine and human phenotypic markers used to identify Bregs, their induction, maintenance, and mechanisms of immune suppression. We highlight recent advances in the field including their use as biomarkers to predict allograft rejection, in-vitro expansion of Bregs, and the effects of commonly used immunosuppressive drugs on their induction and frequency.

SUMMARY

Clinical data continue to emerge in support of Bregs playing an important role in preventing transplant rejection. Hence, it is necessary for the transplant field to better comprehend the mechanisms of Breg induction and approaches to preserve or even enhance their activity to improve long-term transplant outcomes.

CD9+ Regulatory B Cells Induce T Cell Apoptosis via IL-10 and Are Reduced in Severe Asthmatic Patients

CD9 was recently identified as a marker of murine IL-10-competent regulatory B cells. Functional impairments or defects in CD9⁺ IL-10-secreting regulatory B cells are associated with enhanced asthma-like inflammation and airway hyperresponsiveness. In mouse models, all asthma-related features can be abrogated by CD9⁺ B cell adoptive transfer. We aimed herein to decipher the profiles, features, and molecular mechanisms of the regulatory properties of CD9⁺ B cells in human and mouse. The profile of CD9⁺ B cells was analyzed using blood from severe asthmatic patients and normal and asthmatic mice by flow cytometry. The regulatory effects of mouse CD9⁺ B cells on effector T cell death, cell cycle arrest, apoptosis, and mitochondrial depolarization were determined using yellow dye, propidium iodide, Annexin V, and JC-1 staining. MAPK phosphorylation was analyzed by western blotting. Patients with severe asthma and asthmatic mice both harbored less CD19⁺CD9⁺ B cells, although these cells displayed no defect in their capacity to induce T cell apoptosis. Molecular mechanisms of regulation of CD9⁺ B cells characterized in mouse showed that they induced effector T cell cycle arrest in sub G0/G1, leading to apoptosis in an IL-10-dependent manner. This process occurred through MAPK phosphorylation and activation of both the intrinsic and extrinsic pathways. This study characterizes the molecular mechanisms underlying the regulation of CD9⁺ B cells to induce effector T cell apoptosis in mice and humans via IL-10 secretion. Defects in CD9⁺ B cells in blood from patients with severe asthma reveal new insights into the lack of regulation of inflammation in these patients.

Regulatory and Effector B Cells: A New Path Toward Biomarkers and Therapeutic Targets to Improve Transplant Outcomes?

B cells shape the alloimmune response through polarized subsets. These cells inhibit or promote immune responses by expressing suppressive or proinflammatory cytokines. Their summed activity dictates the influence of B cells on the alloimmune response. We review the evidence for regulatory B cells and effector B cells in mice and humans, discuss current limitations in their phenotypic identification, and discuss regulatory B cells as a signature for clinical renal allograft tolerance and predictive markers for allograft outcomes. We discuss the effects of therapeutic agents on regulatory B cells and potential approaches to augment their numbers as a therapeutic tool.

Interleukin-13 suppresses interleukin-10 via inhibiting A20 in peripheral B cells of patients with food allergy

The regulatory B cells (Breg) are important in the body immunity. The differentiation process of Breg is not fully understood yet. Ubiquitin A20 has immune regulatory functions. This study aims to investigate the role of A20 in the regulation of interleukin (IL)-10 in B cells. In this study, B cells were isolated from the peripheral blood samples of healthy subjects and patients with food allergy (FA). The B cells were analyzed by flow cytometry, real time RT-PCR, Western blotting and chromatin immunoprecipitation. We observed that the frequency of Breg and the levels of A20 in B cells were markedly lower in FA patients than in healthy controls. In vitro deletion of A20 compromised the expression of IL-10. B cells in FA patients showed higher levels of histone deacetylase (HDAC)-11 than in healthy subjects. Exposure to IL-13 in the culture induced high levels of HDAC11 in B cells. IL-13 also repressed the expression of A20 in B cells, in which HDAC11 played a critical role via inducing the chromatin remoldeling at the IL-10 promoter locus. Mice with A20-deficient B cells are prone to FA. In summary, ubiquitin A20 can increase the IL-10 expression in B cells, which can be affected by the IL-13-induced HDAC11. To inhibit HDAC11 may have therapeutic potential for FA.

Micro RNA-155 plays a critical role in the initiation of food allergen-related inflammation in the intestine

The pathogenesis of food allergy (FA) is to be further investigated. Regulatory B cells (B10 cell) play a critical in the maintenance of the homeostasis in the intestine. Deregulation of B10 cell is associated with immune inflammation. Micro RNA (miR) 155 is involved in affecting immune cell function. This study tests a hypothesis that miR-155 affects the B10 cell function to facilitate the initiation of FA. In this study, BALB/c mice were sensitized to ovalbumin (OVA) to induce FA-like inflammation in the intestine. B cells were isolated from the intestine by magnetic cell sorting. The expression of miR-155 and IL-10 in B cells was assessed by real time RT-PCR. The results showed that mice sensitized to OVA showed FA-like inflammation and lower frequency of B10 cell in the intestine. B cells isolated from the intestine of FA mice showed higher levels of miR-155 and lower levels of IL-10. Although all the three T helper (Th)2 cytokines, including interleukin (IL)-4, IL-5 and IL-13, were higher in the serum, only IL-13 was positively correlated with the levels of miR-155 in the intestinal B cells. Exposure to IL-13 in the culture markedly increased the expression of miR-155 and suppressed the expression of IL-10 in B cells. Blocking miR-155 abolished the IL-13-induced IL-10 suppression in B cells and inhibited FA response in mice. In conclusion, miR-155 plays a critical role in the initiation of FA in mice. Blocking miR-155 has therapeutic potential in the treatment of FA.

Application of the adverse outcome pathway (AOP) concept to structure the available in vivo and in vitro mechanistic data for allergic sensitization to food proteins

BACKGROUND

The introduction of whole new foods in a population may lead to sensitization and food allergy. This constitutes a potential public health problem and a challenge to risk assessors and managers as the existing understanding of the pathophysiological processes and the currently available biological tools for prediction of the risk for food allergy development and the severity of the reaction are not sufficient. There is a substantial body of in vivo and in vitro data describing molecular and cellular events potentially involved in food sensitization. However, these events have not been organized in a sequence of related events that is plausible to result in sensitization, and useful to challenge current hypotheses. The aim of this manuscript was to collect and structure the current mechanistic understanding of sensitization induction to food proteins by applying the concept of adverse outcome pathway (AOP).

MAIN BODY

The proposed AOP for food sensitization is based on information on molecular and cellular mechanisms and pathways evidenced to be involved in sensitization by food and food proteins and uses the AOPs for chemical skin sensitization and respiratory sensitization induction as templates. Available mechanistic data on protein respiratory sensitization were included to fill out gaps in the understanding of how proteins may affect cells, cell-cell interactions and tissue homeostasis. Analysis revealed several key events (KE) and biomarkers that may have potential use in testing and assessment of proteins for their sensitizing potential.

CONCLUSION

The application of the AOP concept to structure mechanistic in vivo and in vitro knowledge has made it possible to identify a number of methods, each addressing a specific KE, that provide information about the food allergenic potential of new proteins. When applied in the context of an integrated strategy these methods may reduce, if not replace, current animal testing approaches. The proposed AOP will be shared at the www.aopwiki.org platform to expand the mechanistic data, improve the confidence in each of the proposed KE and key event relations (KERs), and allow for the identification of new, or refinement of established KE and KERs.

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.

Curcumin ameliorates experimental autoimmune myasthenia gravis by diverse immune cells

Curcumin is a traditional Asian medicine with diverse immunomodulatory properties used therapeutically in the treatment of many autoimmune diseases. However, the effects of curcumin on myasthenia gravis (MG) remain undefined. Here we investigated the effects and potential mechanisms of curcumin in experimental autoimmune myasthenia gravis (EAMG). Our results demonstrated that curcumin ameliorated the clinical scores of EAMG, suppressed the expression of T cell co-stimulatory molecules (CD80 and CD86) and MHC class II, down-regulated the levels of pro-inflammatory cytokines (IL-17, IFN-γ and TNF-α) and up-regulated the levels of the anti-inflammatory cytokine IL-10, shifted the balance from Th1/Th17 toward Th2/Treg, and increased the numbers of NKR-P1(+) cells (natural killer cell receptor protein 1 positive cells, including NK and NKT cells). Moreover, the administration of curcumin promoted the differentiation of B cells into a subset of B10 cells, increased the anti-R97-166 peptide IgG1 levels and decreased the relative affinity indexes of anti-R97-116 peptide IgG. In summary, curcumin effectively ameliorate EAMG, indicating that curcumin may be a potential candidate therapeutic agent for MG.

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.

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

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

A regulatory CD9(+) B-cell subset inhibits HDM-induced allergic airway inflammation

BACKGROUND

Exposure to respiratory allergens triggers airway hyperresponsiveness and inflammation characterized by the expansion of TH 2 cells and the production of allergen specific IgE. Allergic asthma is characterized by an alteration in immune regulatory mechanisms leading to an imbalance between pro- and anti-inflammatory components of the immune system.

AIMS

Recently B cells have been described as central regulators of exacerbated inflammation, notably in the case of autoimmunity. However, to what extent these cells can regulate airway inflammation and asthma remains to be elucidated.

MATERIALS & METHODS

We took advantage of a allergic asthma model in mice induced by percutaneous sensitization and respiratory challenge with an extract of house dust mite.

RESULTS

In this study, we showed that the induction of allergic asthma alters the homeostasis of IL-10(+) Bregs and favors the production of inflammatory cytokines by B cells. Deeper transcriptomic and phenotypic analysis of Bregs revealed that they were enriched in a CD9(+) B cell subset. In asthmatic mice the adoptive transfer of CD9(+) B cells normalized airway inflammation and lung function by inhibiting TH 2- and TH 17-driven inflammation in an IL-10-dependent manner, restoring a favorable immunological balance in lung tissues. Indeed we further showed that injection of CD9(+) Bregs controls the expansion of lung effector T cells allowing the establishment of a favorable regulatory T cells/effector T cells ratio in lungs.

CONCLUSION

This finding strengthens the potential for Breg-targeted therapies in allergic asthma.

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

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

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.

Regulatory B cells in allergic airways disease and asthma

B cells have long been known to participate in both innate and adaptive immune responses by contributing to antigen presentation and by producing antigen-specific antibodies. Recent evidence shows that certain B-cell subsets can also inhibit T-cell immune responses. Like regulatory T cells (Treg), these regulatory B cells (Breg) appear to comprise several subpopulations. How Breg cells are generated and how they control immune responses in vivo are just beginning to be elucidated. Here, we provide detailed instructions for the identification, isolation, and functional characterization of Breg cells in a murine model of allergic airway disease.

CD24(hi)CD27(+) B cells from patients with allergic asthma have impaired regulatory activity in response to lipopolysaccharide

BACKGROUND

Regulatory B cells have been identified that strongly reduce allergic and auto-immune inflammation in experimental models by producing IL-10. Recently, several human regulatory B-cell subsets with an impaired function in auto-immunity have been described, but there is no information on regulatory B cells in allergic asthma.

OBJECTIVE

In this study, the frequency and function of IL-10 producing B-cell subsets in allergic asthma were investigated.

METHODS

Isolated peripheral blood B cells from 13 patients with allergic asthma and matched healthy controls were analyzed for the expression of different regulatory B-cell markers. Next, the B cells were activated by lipopolysaccharide (LPS), CpG or through the B-cell receptor, followed by co-culture with endogenous memory CD4(+) T cells and house dust mite allergen DerP1.

RESULTS

Lower number of IL-10 producing B cells were found in patients in response to LPS, however, this was not the case when B cells were activated through the B-cell receptor or by CpG. Further dissection showed that only the CD24(hi)CD27(+) B-cell subset was reduced in number and IL-10 production to LPS. In response to DerP1, CD4(+) T cells from patients co-cultured with LPS-primed total B cells produced less IL-10 compared to similar cultures from controls. These results are in line with the finding that sorted CD24(hi)CD27(+) B cells are responsible for the induction of IL-10(+) CD4(+) T cells.

CONCLUSIONS

Taken together, these data indicate that CD24(hi)CD27(+) B cells from allergic asthma patients produce less IL-10 in response to LPS leading to a weaker IL-10 induction in T cells in response to DerP1, which may play a role in allergic asthma.

Impaired function of CD19(+) CD24(hi) CD38(hi) regulatory B cells in patients with pemphigus

BACKGROUND

Pemphigus is an organ-specific autoimmune bullous disease.

OBJECTIVES

To determine the role of regulatory B cells (Bregs) in patients with pemphigus.

METHODS

The frequency of the occurrence of CD19(+) CD24(hi) CD38(hi) Bregs was detected from 34 patients with pemphigus and 20 healthy controls. Interleukin (IL)-10 secretion was processed after stimulating B cells. Specific antidesmoglein antibody (Ab) titres and their subclasses were also measured. Ab response and cytokine production from peripheral blood mononuclear cells (PBMCs) with or without Bregs were analysed.

RESULTS

The number of Bregs was significantly increased in patients with pemphigus compared with healthy controls (15 ± 7% vs. 9 ± 3%; P < 0·01) and the proportion of Bregs in the active groups (newly diagnosed and chronic active patients) was significantly higher than in remittent individuals (16 ± 7% vs. 13 ± 8%; P = 0·04). The IL-10-producing B cells were significantly increased upon stimulation both in patients and in healthy controls. However, the increase ratio of IL-10-producing B cells between short- and long-term stimulation was significantly lower in patients with pemphigus (1·0-fold vs. 2·6-fold increase in control group; P < 0·01). Strikingly, Bregs from the controls were able to suppress interferon (IFN)-γ expression and T helper cell 1 (Th1) immune response (26% inhibition rate), while the suppressive function of Bregs from patients with pemphigus was significantly decreased (9% inhibition rate). There was no difference in Ab levels from PBMCs with or without Bregs after stimulation.

CONCLUSIONS

Bregs in patients with pemphigus are elevated but with defective regulatory function on Th1 cells.

Regulatory functions of B cells in allergic diseases

B cells are essentially described for their capacity to produce antibodies ensuring anti-infectious immunity or deleterious responses in the case of autoimmunity or allergy. However, abundant data described their ability to restrain inflammation by diverse mechanisms. In allergy, some regulatory B-cell subsets producing IL-10 have been recently described as potent suppressive cells able to restrain inflammatory responses both in vitro and in vivo by regulatory T-cell differentiation or directly inhibiting T-cell-mediated inflammation. A specific deficit in regulatory B cells participates to more severe allergic inflammation. Induction of allergen tolerance through specific immunotherapy induces a specific expansion of these cells supporting their role in establishment of allergen tolerance. However, the regulatory functions carried out by B cells are not exclusively IL-10 dependent. Indeed, other regulatory mechanisms mediated by B cells are (i) the production of TGF-β, (ii) the promotion of T-cell apoptosis by Fas-Fas ligand or granzyme-B pathways, and (iii) their capacity to produce inhibitory IgG4 and sialylated IgG able to mediate anti-inflammatory mechanisms. This points to Bregs as interesting targets for the development of new therapies to induce allergen tolerance. In this review, we highlight advances in the study of regulatory mechanisms mediated by B cells and outline what is known about their phenotype as well as their suppressive role in allergy from studies in both mice and humans.

Regulatory T cells and immune regulation of allergic diseases: roles of IL-10 and TGF-β

The prevalence of allergic diseases has significantly increased in industrialized countries. Allergen-specific immunotherapy (AIT) remains as the only curative treatment. The knowledge about the mechanisms underlying healthy immune responses to allergens, the development of allergic reactions and restoration of appropriate immune responses to allergens has significantly improved over the last decades. It is now well-accepted that the generation and maintenance of functional allergen-specific regulatory T (Treg) cells and regulatory B (Breg) cells are essential for healthy immune responses to environmental proteins and successful AIT. Treg cells comprise different subsets of T cells with suppressive capacity, which control the development and maintenance of allergic diseases by various ways of action. Molecular mechanisms of generation of Treg cells, the identification of novel immunological organs, where this might occur in vivo, such as tonsils, and related epigenetic mechanisms are starting to be deciphered. The key role played by the suppressor cytokines interleukin (IL)-10 and transforming growth factor (TGF)-β produced by functional Treg cells during the generation of immune tolerance to allergens is now well established. Treg and Breg cells together have a role in suppression of IgE and induction of IgG4 isotype allergen-specific antibodies particularly mediated by IL-10. Other cell types such as subsets of dendritic cells, NK-T cells and natural killer cells producing high levels of IL-10 may also contribute to the generation of healthy immune responses to allergens. In conclusion, better understanding of the immune regulatory mechanisms operating at different stages of allergic diseases will significantly help the development of better diagnostic and predictive biomarkers and therapeutic interventions.

Anti-tuberculosis treatment enhances the production of IL-22 through reducing the frequencies of regulatory B cell

IL-22 has been suggested to play an important role in immune response against Mycobacterium tuberculosis infection. However, the exact role of IL-22 in human tuberculosis (TB) infection remains unclear and the regulatory mechanism of IL-22 response in human TB is unknown. In this study, we observed that successful anti-tuberculosis treatment induced an enhanced and sustained M. tuberculosis antigen-specific IL-22 response, correlated with the decrease of the frequencies of CD19(+)CD5(+)CD1d(+) regulatory B cells. We also found that depletion of CD19(+) B cells significantly enhanced M. tuberculosis antigen-specific IL-22 production by peripheral blood mononuclear cells. More importantly, we observed that purified CD19(+) B cells, and more efficiently, CD19(+)CD5(+)CD1d(+) regulatory B cells, suppressed IL-22 production. In summary, we showed here for the first time that effective anti-tuberculosis treatment restores M. tuberculosis antigen-specific IL-22 response through a novel mechanism by reducing the frequencies of CD19(+)CD5(+)CD1d(+) regulatory B cells in human TB.

Toll-like receptor ligation for the induction of regulatory B cells

Toll-like receptors (TLRs) are key components for the recognition of microorganisms, for the initiation of innate immunity, and for promoting adaptive immune responses. TLR signaling in B cells, in addition to B cell receptor or CD40 ligation, plays an important role in B cell differentiation and activation. In contrast, various infectious agents and/or TLR ligands can also prime B cells to induce tolerance and downregulate inflammatory reactions; those B cells are called regulatory B (Breg) cells and are characterized by a dominant IL-10 production. Several studies have suggested that Breg cells are impaired in patients with autoimmune diseases and allergic asthma. However, the role for TLR ligands in the induction of Breg cells as a potential therapy for some of these inflammatory diseases has not yet been investigated. Here, we provide detailed instructions on how to analyze and validate cytokine production in human and mouse B cells in response to various TLR ligands. Furthermore, we describe an assay to investigate the suppressive properties of TLR-induced B cells to confirm their regulatory B cell status.

Mechanisms of peripheral tolerance to allergens

The immune system is regulated to protect the host from exaggerated stimulatory signals establishing a state of tolerance in healthy individuals. The disequilibrium in immune regulatory vs effector mechanisms results in allergic or autoimmune disorders in genetically predisposed subjects under certain environmental conditions. As demonstrated in allergen-specific immunotherapy and in the healthy immune response to high-dose allergen exposure models in humans, T regulatory cells are essential in the suppression of Th2-mediated inflammation, maintenance of immune tolerance, induction of the two suppressive cytokines interleukin-10 and transforming growth factor-β, inhibition of allergen-specific IgE, and enhancement of IgG4 and IgA. Also, suppression of dendritic cells, mast cells, and eosinophils contributes to the construction of peripheral tolerance to allergens. This review focuses on mechanisms of peripheral tolerance to allergens with special emphasis on recent developments in the area of immune regulation.

Regulatory B cells from hilar lymph nodes of tolerant mice in a murine model of allergic airway disease are CD5+, express TGF-β, and co-localize with CD4+Foxp3+ T cells

In a biphasic, ovalbumin (OVA)-induced murine asthma model where allergic airway disease is followed by resolution and the development of local inhalational tolerance (LIT), transforming growth factor (TGF)-β-expressing CD5(+) B cells were selectively expanded locally in hilar lymph nodes (HLN) of LIT mice. LIT HLN CD5(+) B cells, but not LIT HLN CD5(-) B cells, induced expression of Foxp3 in CD4(+)CD25(-) T cells in vitro. These CD5(+) regulatory B cells (Breg) and CD4(+)Foxp3(+) T cells demonstrated similar increases in expression of chemokine receptors (CXCR4 and CXCR5) and co-localized in HLN B cell zones of LIT mice. The adoptive transfer of LIT HLN CD5(+) B cells, but not LIT HLN CD5(-) B cells, increased the number of CD4(+)Foxp3(+) T cells in the lung and inhibited airway eosinophilia in this OVA model. Thus, Breg in HLNs of LIT mice reside in a CD5(+) TGF-β-producing subpopulation and co-localize with CD4(+)Foxp3(+) T cells.

In Vitro Induction of Allergen-Specific Interleukin-10-Producing Regulatory B Cell Responses by Interferon-γ in Non-Immunoglobulin E-Mediated Milk Allergy

PURPOSE

Specific oral immunotherapy (SOIT) using interferon-γ (IFN-γ) has been successful as a food allergy treatment. Interleukin-10 (IL-10)-producing regulatory B cells (Br1s) play a role in immune tolerance to food allergens. In addition, IFN-γ shows tolerogenic effects on allergen-induced Br1 responses.

METHODS

Eleven patients that were allergic to cow's milk and 12 milk-tolerant subjects were selected by double-blind placebo-controlled food challenge (DBPCFC) and clinical characteristics. The immunomodulatory effects of IFN-γ on allergen-specific Br1 responses were evaluated in 6 milk allergy patients and 8 milk-tolerant subjects. Peripheral blood mononuclear cells (PBMCs) from subjects were stimulated with casein and/or IFN-γ and analyzed by flow cytometry.

RESULTS

IFN-γ had no effect on total cell counts or the proportion of Br1 cells in PBMCs. IFN-γ stimulation did not change total Br1 cell counts or the percentage of Br1s among CD5(+) B cells in the milk allergy or the milk-tolerant groups. In the milk allergy group, Br1 counts were not different between the control and the casein stimulation but significantly increased in the IFN-γ + casein stimulated cells, and the Br1 fractions were decreased after casein stimulation and recovered in the addition of IFN-γ for stimulation. In the milk-tolerant group, Br1 counts increased in the casein stimulated cells and in the IFN-γ + casein stimulated cells, but the increase was significantly less when IFN-γ was added, and the Br1 fractions were increased after casein stimulation and IFN-γ + casein stimulation, that was not significant when IFN-γ was added.

CONCLUSIONS

IFN-γ-induced allergen-specific Br1 responses in the PBMCs of milk allergy patients play a role in milk allergen-specific tolerance induction in vitro. Further investigations into the molecular immunological mechanisms underlying the induction of allergen-specific Br1 responses are needed.

Allergen-specific responses of CD19(+)CD5(+)Foxp3(+) regulatory B cells (Bregs) and CD4(+)Foxp3(+) regulatory T cell (Tregs) in immune tolerance of cow milk allergy of late eczematous reactions

Foxp3-expressing cells among CD19(+)CD5(+) B cells were identified as regulatory B cells. Food allergy manifesting as late eczematous reactions is regarded as a non-IgE-mediated food allergy. The diagnosis for milk allergy manifesting as late eczematous reactions was made on the basis of the findings obtained from a double-blind placebo-controlled food challenge in patients with atopic dermatitis. Twelve patients with milk allergy and 12 patients who could tolerate milk were selected. On casein stimulation, the CD19(+)CD5(+)Foxp3(+) B cell (Breg) fraction in CD5(+) B cells decreased from 4.4±1.1% to 3.1±0.7% (P=0.047, n=12) in the milk allergy group and increased from 4.4±1.3% to 5.2±1.4% (P=0.001, n=10) in the milk-tolerant group. On the other hand, on allergen stimulation, the number of CD4(+)Foxp3(+) regulatory T cells (Tregs) in the milk allergy group and milk-tolerant group increased from 2.6±0.7% to 3.4±0.6% (P=0.014, n=9) and from 2.7±1.0% to 3.5±1.0% (P=0.038, n=10), respectively. In conclusion, allergen-specific responses of Bregs, rather than those of Tregs, seem to influence the immune responses (i.e., allergy or tolerance) to a food allergen.