The role of regulatory B cells in allergen immunotherapy

Allergen specific immunotherapy regulates macrophage property in the airways

BACKGROUND

Allergen specific immunotherapy (AIT) has been widely used in allergy clinics. The therapeutic effects of it are to be improved. Macrophages occupy the largest proportion of airway immune cells. The aim of this study is to measure the effects of nasal instillation AIT (nAIT) on airway allergy by regulating macrophage functions.

METHODS

An airway allergy mouse model was established with the ovalbumin-alum protocol. nAIT was conducted for mice with airway allergy through nasal instillation. The effects of nAIT were compared with subcutaneous injection AIT (SCIT) and sublingual AIT (SLIT).

RESULTS

Mice with airway allergy showed the airway allergic response, including lung inflammation, airway hyper responsiveness, serum specific IgE, increase in the amounts of eosinophil peroxidase, mouse mast cell protease-1, and Th2 cytokines in bronchoalveolar lavage fluid. nAIT had a much better therapeutic effect on the airway allergic response than SCIT and SLIT. Mechanistically, we observed better absorption of allergen in macrophages, better production of IL-10 by macrophages, and better immune suppressive functions in macrophages in mice received nAIT than SCIT and SLIT.

CONCLUSIONS

The nAIT has a much better therapeutic effect on suppressing the airway allergic response, in which macrophages play a critical role.

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.

Mechanisms of Allergen Immunotherapy and Potential Biomarkers for Clinical Evaluation

Allergen-immunotherapy (AIT) is an efficacious and disease-modifying treatment option for IgE-mediated diseases. Among these allergic rhinitis, insect venom allergy, food allergy, and allergic asthma are the most common candidates for AIT. AIT gives rise to clinical immunotolerance which may last for years after the treatment cessation. Mechanisms of AIT include suppression of allergic inflammation in target tissues and stimulation of the production of blocking antibodies, especially IgG4 and IgA. These mechanisms are followed by a reduction of underlying allergen-specific Th2 cell-driven responses to the allergens. Tolerance induction takes place through the desensitization of effector cells and stimulation of regulatory T cells that show their effects by mechanisms involving cell-cell cross-talk, but also other mechanisms, e.g., by the production of immunomodulatory cytokines such as, e.g., IL-10 and TGF-beta. From a personalized medical perspective, there is a need for clinical biomarkers of value in selecting responders and optimizing patient care during AIT. Also, a deeper understanding of underlying mechanistic processes will improve AIT's future outcomes. In this paper, the current knowledge of mechanisms in AIT is reviewed with a special focus on biomarkers of this therapy.

Clinical and experimental treatment of allergic asthma with an emphasis on allergen immunotherapy and its mechanisms

Allergen immunotherapy (AIT) is currently the only form of treatment that modifies allergic asthma. Pharmacotherapy alone seeks to control the symptoms of allergic asthma, allergic rhinitis, and other atopic conditions. In contrast, AIT can induce long-term physiological modifications through the immune system. AIT enables individuals to live improved lives many years after treatment ends, where they are desensitized to the allergen(s) used or no longer have significant allergic reactions upon allergen provocation. The leading forms of treatment with AIT involve injections of allergen extracts with increasing doses via the subcutaneous route or drops/tablets via the sublingual route for several years. Since the initial attempts at this treatment as early as 1911 by Leonard Noon, the mechanisms by which AIT operates remain unclear. This literature-based review provides the primary care practitioner with a current understanding of the mechanisms of AIT, including its treatment safety, protocols, and long-term efficacy. The primary mechanisms underlying AIT include changes in immunoglobulin classes (IgA, IgE, and IgG), immunosuppressive regulatory T-cell induction, helper T cell type 2 to helper T cell type 1 cell/cytokine profile shifts, decreased early-phase reaction activity and mediators, and increased production of IL-10, IL-35, TGF-β, and IFN-γ. Using the databases PubMed and Embase, a selective literature search was conducted searching for English, full-text, reviews published between 2015 and 2022 using the keywords (with wildcards) "allerg*," "immunotherap*," "mechanis*," and "asthma." Among the cited references, additional references were identified using a manual search.

Stimulation of naïve B cells with a fusion protein consisting of FlaA and Bet v 1 induces regulatory B cells ex vivo

BACKGROUND

The experimental fusion protein rFlaA:Betv1 was shown to efficiently suppress allergen-specific sensitization in mice. However, the detailed mechanism of rFlaA:Betv1-mediated immune modulation is not fully understood. In this study, we investigated the effect of rFlaA:Betv1 on naïve murine B cells.

METHODS

Immune modulating capacity of rFlaA:Betv1 was screened in IL-10 reporter mice. B cells were isolated from spleens of naïve C57Bl/6, TLR5^-/- , or MyD88^-/- mice, stimulated with rFlaA:Betv1 and controls, and monitored for the expression of the regulatory B cell markers CD1d, CD24, CD38, and surface IgM by flow cytometry. Secreted cytokines, antibodies, and reactivity of the induced antibodies were investigated by ELISA and intracellular flow cytometry. Suppressive capacity of rFlaA:Betv1-stimulated B cells was tested in mDC:CD4⁺ T cell:B cell triple cultures.

RESULTS

Upon in vivo application of rFlaA:Betv1 into IL-10-GFP reporter mice, CD19⁺ B cells were shown to produce anti-inflammatory IL-10, suggesting B cells to contribute to the immune-modulatory properties of rFlaA:Betv1. rFlaA:Betv1-induced IL-10 secretion was confirmed in human B cells isolated from buffy coats. In vitro stimulation of naïve murine B cells with rFlaA:Betv1 resulted in an mTOR- and MyD88-dependent production of IL-10 and rFlaA:Betv1 induced Bet v 1-reactive IgG production, which was not observed for IgA. rFlaA:Betv1-stimulated B cells formed a CD19⁺ CD24⁺ CD1d⁺ IgM⁺ CD38⁺ Breg subpopulation capable of suppressing Bet v 1-induced TH2 cytokine secretion in vitro.

CONCLUSION

rFlaA:Betv1 can act as a thymus-independent B cell antigen, stimulating the mTOR- and MyD88-dependent differentiation of B cells displaying a regulatory phenotype, IL-10 secretion, antigen-binding antibody production, and a suppressive capacity in vitro.

Current Insight into the Role of IL-35 and Its Potential Involvement in the Pathogenesis and Therapy of Atopic Dermatitis

Interleukin 35 (IL-35), a new member of the IL-12 family of heterodimeric cytokines, could induce two different types of regulatory cells including regulatory T and B cells such as IL-35-induced regulatory T cells and IL-10-producing regulatory B cells (IL-10+Bregs), and IL-35-producing regulatory B cells (IL-35+Bregs). These cells appear to play an important role in modulating the immune system in numerous diseases. Several findings suggested that the expression of IL-35 is dysregulated in many autoimmune, inflammatory, and allergic diseases. Due to the functions of IL-35, it seems that this cytokine may act as an efficient therapeutic strategy for numerous conditions including atopic dermatitis (AD). We aimed to provide a comprehensive overview of the role of IL-35 in modulating the immune system. Additionally, we highlight IL-35 as a specific immunological target, discuss its possible involvement in the pathogenesis of AD, and hypothesize that IL-35 may become a novel target for the treatment of AD. However, further studies are required to evaluate this hypothesis.

Sphingosine-1-phosphate/TGF-β axis drives epithelial mesenchymal transition in asthma-like disease

BACKGROUND AND PURPOSE

Airway remodelling is a critical feature of chronic lung diseases. Epithelial-mesenchymal transition (EMT) represents an important source of myofibroblasts, contributing to airway remodelling. Here, we investigated the sphingosine-1-phosphate (S1P) role in EMT and its involvement in asthma-related airway dysfunction.

EXPERIMENTAL APPROACH

A549 cells were used to assess the S1P effect on EMT and its interaction with TGF-β signalling. To assess the S1P role in vivo and its impact on lung function, two experimental models of asthma were used by exposing BALB/c mice to subcutaneous administration of either S1P or ovalbumin (OVA).

KEY RESULTS

Following incubation with TGF-β or S1P, A549 acquire a fibroblast-like morphology associated with an increase of mesenchymal markers and down-regulation of the epithelial. These effects are reversed by treatment with the TGF-β receptor antagonist LY2109761. Systemic administration of S1P to BALB/c mice induces asthma-like disease characterized by mucous cell metaplasia and increased levels of TGF-β, IL-33 and FGF-2 within the lung. The bronchi harvested from S1P-treated mice display bronchial hyperresponsiveness associated with overexpression of the mesenchymal and fibrosis markers and reduction of the epithelial.The S1P-induced switch from the epithelial toward the mesenchymal pattern correlates to a significant increase of lung resistance and fibroblast activation. TGF-β blockade, in S1P-treated mice, abrogates these effects. Finally, inhibition of sphingosine kinases by SK1-II in OVA-sensitized mice, abrogates EMT, pulmonary TGF-β up-regulation, fibroblasts recruitment and airway hyperresponsiveness.

CONCLUSION AND IMPLICATIONS

Targeting S1P/TGF-β axis may hold promise as a feasible therapeutic target to control airway dysfunction in asthma.

Clostridium leptum induces the generation of interleukin-10+ regulatory B cells to alleviate airway inflammation in asthma

BACKGROUND AND OBJECTIVE

Asthma is one of the most common chronic inflammatory diseases of the respiratory tract. Previous studies have shown that the reduction of regulatory B cells (Bregs) can increase inflammation of the body and promote the formation of chronic airway inflammation in asthma, but the detailed mechanisms have not been fully elucidated. The intestinal flora Clostridium leptum (CL) has been reported to modulate immune regulatory cells in the body, but the specific mechanisms are not clear. This study aimed to investigate the effects of CL on the differentiation of interleukin (IL)- 10⁺ Bregs and the regulation of the asthmatic inflammation-associated immune network.

METHODS

The abundances of CL and the frequencies of blood Bregs from asthmatic patients and healthy controls were compared. The house dust mite (HDM)-induced asthma model was established in mice. The effects of CL exposure and B cell infusion on Breg differentiation, T cell cytokine production, and inflammatory cell infiltration in mouse lungs were examined. Bregs were cocultured with regulatory T cells (Tregs) and CD4⁺ non-Tregs to evaluate their roles on Foxp3 expression and T cell differentiation, respectively.

RESULTS

Compared with healthy controls, asthmatic patients had significantly reduced frequencies of blood Bregs and abundances of fecal CL, and these two parameters were positively correlated. In the asthma model, the frequencies of Bregs in lungs were significantly reduced; while the infusion of Bregs isolated from CL- supplemented mice significantly reduced airway inflammation and hyperresponsiveness. In addition, Bregs inhibited the differentiation of cocultured non-Tregs into multiple effector cells and enhanced Foxp3 expression in cocultured Tregs.

CONCLUSION

Bregs contribute to the alleviation of airway inflammation, which provides insight on implementing CL-based microbial induction of Bregs in asthma therapy.

Identification of Robust Biomarkers for Early Predicting Efficacy of Subcutaneous Immunotherapy in Children With House Dust Mite-Induced Allergic Rhinitis by Multiple Cytokine Profiling

Background

Subcutaneous immunotherapy (SCIT) is an effective treatment for children with allergic rhinitis (AR), but its efficacy fluctuates among patients. There are no reliable candidate biomarkers for monitoring and predicting the response to SCIT. The present study aims to identify novel biomarkers for early predicting the efficacy of SCIT in pediatric AR patients based on multiple cytokine profiling.

Methods

We prospectively recruited 72 children with house dust mite (HDM)-induced AR who were assigned to receive SCIT. The serum samples were collected and multiple cytokine profiling was conducted by Luminex assay at baseline. All patients were followed-up for 1 year and then categorized into effective and ineffective group based on their efficacy, and levels of 48 selected cytokines were tested and compared between the two groups. The potential cytokines were further validated by enzyme-linked immunosorbent assay (ELISA) in a cohort with 54 responders and 26 non-responders.

Results

Sixty-nine of 72 children completed one-year follow-up schedule with 46 included in effective group and 23 in ineffective group. The results of multiple cytokine profiling showed that 15 cytokines (eotaxin, G-CSF, GM-CSF, IFN-γ, IL-12(p40), IL-13, IL-15, IL-16, IL-4, MIF, MIP-1α, RANTES, SCF, SDF-1α and VEGF) were dysregulated between effective and ineffective group (all P < 0.05). Unadjusted and adjusted multivariate analysis models highlighted that serum eotaxin, IFN-γ, IL-4 and MIF levels closely associated with the efficacy of SCIT in pediatric HDM-induced AR patients. In addition, receiver operating characteristic (ROC) curves revealed potential values of these four biomarkers in predicting the response to SCIT. Further ELISA validation results in the cohort of 80 pediatric patients demonstrated that serum eotaxin and IL-4 levels were elevated in responders while IFN-γ levels decreased in responders (all P < 0.05). ROC curves demonstrated that serum IL-4 exhibited more reliable accuracy in predicting SCIT efficacy than eotaxin and IFN-γ.

Conclusion

Our discover–validation study suggested that cytokines including IL-4, eotaxin and IFN- γ may serve as robust biomarkers for early predicting response of SCIT in children with HDM-induced AR. These results strengthen the evidence that cytokines were associated with the response of SCIT and contributed to understand its underlying therapeutic mechanisms.

Basics of immunotherapy for epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most lethal of all gynecological cancers. Despite excellent responses to standard treatment in approximately 70% of patients, most of them will relapse within 5 years of initial treatment and many of them will develop chemotherapy-resistant disease. It is then important to find other means of treatment for these patients such as immunotherapy or targeted therapy. To understand immunotherapy, it is important to explain the dynamic interplay between cancer and the immune system. Compared to traditional tumor therapies, immunotherapy acts primarily on the immune system or the tumor microenvironment but not directly on the tumor cells, and it may also promote synergistic anti-tumor actions as part of a combined treatment. The aim of this narrative review is to provide a basic understanding of immunotherapy the interest of this treatment in EOC, and to present the main ongoing studies that could change patient management in the future.

Immunotherapy With Recombinant Alt a 1 Suppresses Allergic Asthma and Influences T Follicular Cells and Regulatory B Cells in Mice

Background

Alternaria is a major source of asthma-inducing allergens. Allergen-specific immunotherapy improves the progression of allergic asthma. The current treatment is based on crude Alternaria extracts. Alt a 1 is the predominant allergen in Alternaria. However, the treatment efficacy of recombinant Alt a 1 (rAlt a 1) in an asthmatic animal model and its influence on Tfh and Breg cells are unknown.

Objective

To explore the therapeutic treatment effects of rAlt a 1 on the progress of an asthmatic mouse model and its effect on Tfh and Breg cells.

Methods

We synthesized and purified rAlt a 1. Alternaria-sensitized and challenged mice received subcutaneous immunotherapy (SCIT) with four different rAlt a 1 dosages (5, 50, 100, and 150 µg) or PBS only. Finally, lung and airway inflammation, mouse mast cell protease 1 (MMCP-1), serum immunoglobulin responses, Tfh and Breg cell levels, and the correlation between asthmatic features (inflammation grades and IL-4 and IL-10 levels) and these two cell types were measured after Alternaria rechallenge.

Results

High purity and allergenic potency of rAlt a 1 protein were obtained. Following treatment with four different rAlt a 1 dosages, both lung and airway inflammation ameliorated, including lung pathology, serum MMCP-1 levels, inflammatory cell numbers, and cytokine levels in bronchoalveolar lavage fluid (BALF). Additionally, rAlt a 1-SCIT increased the expression of Alternaria-sIgG1, rAlt a 1-sIgG1, rAlt a 1-sIgG2a, and rAlt a 1-sIgG2b in serum. Moreover, the number and percentage of CXCR5⁺PD-1⁺Tfh cells were increased in the PC control, while they decreased in the rAlt a 1-SCIT groups. Meanwhile, the absolute numbers and proportions of Breg cells were evaluated after administration of rAlt a 1. A positive correlation was observed between CXCR5⁺PD-1⁺Tfh cells and inflammation grades (r = 0.50, p = 0.01), as well as a slightly strong positive relationship with IL-4 (r = 0.55, p = 0.005) and IL-10 (r = 0.58, p = 0.003) levels; Breg cells showed an opposite correlation with the grades of inflammation (r = -0.68, p = 0.0003), along with a negative correlation to IL-4 (r = -0.61, p = 0.001) and IL-10 (r = -0.53, p = 0.008) levels.

Conclusions

We verified that treatment with rAlt a 1 can alleviate asthma progression and further have a regulatory effect on Tfh and Breg cells in an Alternaria-induced asthmatic mouse model.

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.

Hymenoptera Venom Immunotherapy: Immune Mechanisms of Induced Protection and Tolerance

Hymenoptera venom allergy is one of the most severe allergic diseases, with a considerable prevalence of anaphylactic reaction, making it potentially lethal. In this review, we provide an overview of the current knowledge and recent findings in understanding induced immune mechanisms during different phases of venom immunotherapy. We focus on protection mechanisms that occur early, during the build-up phase, and on the immune tolerance, which occurs later, during and after Hymenoptera venom immunotherapy. The short-term protection seems to be established by the early desensitization of mast cells and basophils, which plays a crucial role in preventing anaphylaxis during the build-up phase of treatment. The early generation of blocking IgG antibodies seems to be one of the main reasons for the lower activation of effector cells. Long-term tolerance is reached after at least three years of venom immunotherapy. A decrease in basophil responsiveness correlates with tolerated sting challenge. Furthermore, the persistent decline in IgE levels and, by monitoring the cytokine profiles, a shift from a Th2 to Th1 immune response, can be observed. In addition, the generation of regulatory T and B cells has proven to be essential for inducing allergen tolerance. Most studies on the mechanisms and effectiveness data have been obtained during venom immunotherapy (VIT). Despite the high success rate of VIT, allergen tolerance may not persist for a prolonged time. There is not much known about immune mechanisms that assure long-term tolerance post-therapy.

Biology and dynamics of B cells in the context of IgE-mediated food allergy

An increasing number of people suffer from IgE-mediated food allergies. The immunological mechanisms that cause IgE-mediated food allergy have been extensively studied. B cells play a key role in the development of IgE-mediated food allergies through the production of allergen-specific antibodies. While this particular function of B cells has been known for many years, we still do not fully understand the mechanisms that regulate the induction and maintenance of allergen-specific IgE production. It is still not fully understood where in the body IgE class switch recombination of food allergen-specific B cells occurs, and what processes are involved in the immunological memory of allergen-specific IgE responses. B cells can also contribute to the regulation of allergen-specific immune responses through other mechanisms such as antigen presentation and cytokine production. Recent technological advances have enabled highly detailed analysis of small subsets of B cells down to the single-cell level. In this review, we provide an overview of the current knowledge on the biology of B cells in relation to IgE-mediated food allergies.

TGF-β-secreting regulatory B cells: unsung players in immune regulation

Regulatory B cells contribute to the regulation of immune responses in cancer, autoimmune disorders, allergic conditions and inflammatory diseases. Although most studies focus on regulatory B lymphocytes expressing interleukin-10, there is growing evidence that B cells producing transforming growth factor β (TGF-β) can also regulate T-cell immunity in inflammatory diseases and promote the emergence of regulatory T cells that contribute to the induction and maintenance of natural and induced immune tolerance. Most research on TGF-β⁺ regulatory B cells has been conducted in models of allergy, cancer and autoimmune diseases, but there has, as yet, been limited scrutiny of their role in the transplant setting. Herein, we review recent investigations seeking to understand how TGF-β-producing B cells direct the immune response in various inflammatory diseases and whether these regulatory cells may have a role in fostering tolerance in transplantation.

Immunological Responses and Biomarkers for Allergen-Specific Immunotherapy Against Inhaled Allergens

Long-term efficacy that occurs with allergen immunotherapy of proven value is associated with decreases in IgE-dependent activation of mast cells and tissue eosinophilia. This suppression of type 2 immunity is accompanied by early induction of regulatory T cells, immune deviation in favor of T_H1 responses, and induction of local and systemic IgG, IgG₄, and IgA antibodies. These "protective" antibodies can inhibit allergen-IgE complex formation and consequent mast cell triggering and IgE-facilitated T_H2-cell activation. Recent studies have highlighted the importance of innate responses mediated by type 2 dendritic cells and innate lymphoid cells in allergic inflammation. These cell types are under the regulation of cytokines such as thymic stromal lymphopoietin and IL-33 derived from the respiratory epithelium. Novel subsets of regulatory cells induced by immunotherapy include IL-35-producing regulatory T cells, regulatory B cells, a subset of T follicular regulatory cells, and IL-10-producing group 2 innate lymphoid cells. These mechanisms point to biomarkers that require testing for their ability to predict clinical response to immunotherapy and to inform novel approaches for better efficacy, safety, and long-term tolerance.

Mechanisms of Drug Desensitization: Not Only Mast Cells

Drug desensitization (DD) allows transient clinical tolerance to the drug in reactive patients and it is frequently and successfully used in the management of both IgE and non IgE-mediated hypersensitivity reactions (HRs). The underlying mechanisms behind this process is not well understood. The desensitization procedure is associated with the inhibition of mast cells degranulation and cytokine production, that, is attributable, at least partially, to the abrogation of Ca2+ mobilization; in vitro findings and in vivo mouse models of rapid desensitization show that the organization and spatial distribution of actin is critical for Ca2+ mobilization. Some clinical observations may suggest the induction of a longer memory of tolerance by DD and they raise the suspicion that other cells and mechanisms are involved in DD. Some data are emerging about the modifications of immune responses during DD in patients with previous immediate HRs. In particular, an increase of regulatory cytokines, mainly represented by IL-10, has been shown, and more importantly, the appearance of IL-35 producing T regulatory cells has been described during DD. The release of controlled cellular mediators by mast cells over time and the development of the antigen-specific regulation of adaptive response allow to safely and successfully reach the target dose of a first line drug during DD.

The Potential Role of Regulatory B Cells in Idiopathic Membranous Nephropathy

Regulatory B cells (Breg) are widely regarded as immunomodulatory cells which play an immunosuppressive role. Breg inhibits pathological autoimmune response by secreting interleukin-10 (IL-10), transforming growth factor-β (TGF-β), and adenosine and through other ways to prevent T cells and other immune cells from expanding. Recent studies have shown that different inflammatory environments induce different types of Breg cells, and these different Breg cells have different functions. For example, Br1 cells can secrete IgG4 to block autoantigens. Idiopathic membranous nephropathy (IMN) is an autoimmune disease in which the humoral immune response is dominant and the cellular immune response is impaired. However, only a handful of studies have been done on the role of Bregs in this regard. In this review, we provide a brief overview of the types and functions of Breg found in human body, as well as the abnormal pathological and immunological phenomena in IMN, and propose the hypothesis that Breg is activated in IMN patients and the proportion of Br1 can be increased. Our review aims at highlighting the correlation between Breg and IMN and proposes potential mechanisms, which can provide a new direction for the discovery of the pathogenesis of IMN, thus providing a new strategy for the prevention and early treatment of IMN.

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.

Regulatory B cells control airway hyperreactivity and lung remodeling in a murine asthma model

BACKGROUND

Asthma is a widespread, multifactorial chronic airway disease. The influence of regulatory B cells on airway hyperreactivity (AHR) and remodeling in asthma is poorly understood.

OBJECTIVE

Our aim was to analyze the role of B cells in a house dust mite (HDM)-based murine asthma model.

METHODS

The influence of B cells on lung function, tissue remodeling, and the immune response were analyzed by using wild-type and B-cell-deficient (μMT) mice and transfer of IL-10-proficient and IL-10-deficient B cells to μMT mice.

RESULTS

After HDM-sensitization, both wild-type and μMT mice developed AHR, but the AHR was significantly stronger in μMT mice, as confirmed by 2 independent techniques: invasive lung function measurement in vivo and examination of precision-cut lung slices ex vivo. Moreover, airway remodeling was significantly increased in allergic μMT mice, as shown by enhanced collagen deposition in the airways, whereas the numbers of FoxP3⁺ and FoxP3^- IL-10-secreting regulatory T cells were reduced. Adoptive transfer of IL-10-proficient but not IL-10-deficient B cells into μMT mice before HDM-sensitization attenuated AHR and lung remodeling. In contrast, FoxP3⁺ regulatory T cells were equally upregulated by transfer of IL-10-proficient and IL-10-deficient B cells.

CONCLUSION

Our data in a murine asthma model illustrate a central role of regulatory B cells in the control of lung function and airway remodeling and may support future concepts for B-cell-targeted prevention and treatment strategies for allergic asthma.

Tolerance mechanisms in allergen immunotherapy

PURPOSE OF REVIEW

Allergen immunotherapy is the only treatment modality which alters the natural course of allergic diseases by restoring immune tolerance against allergens. Deeper understanding of tolerance mechanisms will lead to the development of new vaccines, which target immune responses and promote tolerance.

RECENT FINDINGS

Successful allergen immunotherapy (AIT) induces allergen-specific peripheral tolerance, characterized mainly by the generation of allergen-specific Treg cells and reduction of Th2 cells. At the early phase, AIT leads to a decrease in the activity and degranulation of mast cells and basophils and a decrease in inflammatory responses of eosinophils in inflamed tissues. Treg cells show their effects by secreting inhibitory cytokines including interleukin (IL)-10, transforming growth factor-β, interfering with cellular metabolisms, suppressing antigen presenting cells and innate lymphoid cells (ILCs) and by cytolysis. AIT induces the development of regulatory B cells producing IL-10 and B cells expressing allergen-specific IgG4. Recent investigations have demonstrated that AIT is also associated with the formation of ILC2reg and DCreg cells which contribute to tolerance induction.

SUMMARY

Research done so far, has shown that multiple molecular and cellular factors are dysregulated in allergic diseases and modified by AIT. Studies should now focus on finding the best target and ideal biomarkers to identify ideal candidates for AIT.

B-cell responses in allergen immunotherapy

PURPOSE OF REVIEW

The establishment of long-term clinical tolerance in AIT requires the involvement of basophils, mast cells, allergen-specific regulatory T and B cells, downregulation of effector type 2 responses, and increase in production of specific IgG, particularly immunglobulin G4 (IgG4) antibodies. This review aims to provide an overview of the role of B cells in AIT, their mechanism of action, and their potential for improving AIT.

RECENT FINDINGS

In-depth research of B cells has paved the way for improved diagnosis and research on allergic diseases. B cells play a central role in allergy and allergen tolerance through the production of immunglobulin E (IgE)-blocking antibodies. However, an increasing body of evidence has emerged supporting a role for B cells in regulating immune responses that extends beyond the production of antibodies. Regulatory B cells play an important role in immunosuppression, mediated by secretion of anti-inflammatory cytokines.

SUMMARY

Successful AIT establishes the reinstatement of immune tolerance toward allergens, reduces allergic symptoms, and improves clinical treatments in patients. B cells play a central role in this process through antibody-independent immune regulatory processes in addition to the production of IgE-blocking antibodies.

Regulatory B Cells: Dark Horse in Pregnancy Immunotherapy?

There are many unanswered questions surrounding the function of immune cells and how they interact with the reproductive system to support successful pregnancy or contribute to pregnancy pathologies. While the role of immune cells such as uterine natural killer and dendritic cells, and more recently regulatory T cells has been established, the role of another major immune cell population, the B cell, and particularly the regulatory B cells, is relatively poorly understood. This review outlines what is known about B-cell subsets in the context of pregnancy, what constitutes a regulatory B cell and what role they may play, particularly during early pregnancy. Lastly, we discuss why immunotherapies for the treatment of pregnancy disorders is not widely progressed clinically and speculate on the potential of functional regulatory B cells as the basis of novel immunotherapeutic approaches for the treatment of immune-based pregnancy pathologies.

Asthma immunotherapy and treatment approaches with mesenchymal stem cells

Asthma is a chronic inflammatory disease of the airways where exaggerated T helper 2 immune responses and inflammatory mediators play a role. Current asthma treatment options can effectively suppress symptoms and control the inflammatory process; however, cannot modulate the dysregulated immune response. Allergen-specific immunotherapy is one of the effective treatments capable of disease modification. Injecting allergens under the skin in allergen-specific immunotherapy can reduce asthma and improve the sensitivity of the lungs, however, has a risk of severe reactions. Mesenchymal stem cells have immunoregulatory activity with their soluble mediators and contact dependent manner. In this review, we focus on the current treatment strategies with mesenchymal stem cells in asthma as a new therapeutic tool and compare those with immunotherapy.

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.

Induction of IgG2 and IgG4 B-cell memory following sublingual immunotherapy for ryegrass pollen allergy

BACKGROUND

While treatment for atopic rhinitis is aimed mostly to relieve symptoms, only allergen-specific immunotherapy (AIT) is targeted to modify the natural history of allergic diseases. This results in sustained clinical tolerance, even when treatment has stopped. The immunomodulatory effects of AIT are attributed mainly to increased regulatory T-cell function and increased allergen-specific IgG₄ , yet little is known about the effect on the memory B-cell compartment.

OBJECTIVE

We aimed to examine the effects of AIT on the IgE- and IgG subclass-expressing memory B cells.

METHODS

We recruited 29 patients with atopic seasonal rhinoconjunctivitis and performed a longitudinal analysis of the peripheral immune compartment before, during, and after sublingual immunotherapy (SLIT) for allergy to temperate grass pollen, predominantly to ryegrass pollen (RGP; Lolium perenne). Using flow cytometry on peripheral blood mononuclear cells and serum immunoassays, we analyzed the effects of a 4 months preseasonal treatment regimen comprising two or three courses in consecutive years on circulating IgE⁺ and IgG⁺ memory B cells and allergen-specific Ig levels.

RESULTS

SLIT increased RGP-specific serum IgG₂ and IgG₄ , as well as the frequencies of IgG₂ ⁺ and IgG₄ ⁺ memory B cells, whereas no effect was observed on the IgE⁺ memory B-cell compartment. Furthermore, SLIT enhanced proportions of regulatory T cells specific to RGP. These changes were associated with clinical improvement.

CONCLUSION

Our data provide evidence for immunological effects of SLIT on B-cell memory. Skewing responses toward IgG₂ and IgG₄ subclasses might be a mechanism to suppress IgE-mediated allergic responses.

Approaches to inducing antigen-specific immune tolerance in allergy and autoimmunity: Focus on antigen-presenting cells and extracellular vesicles

Increasing prevalence of allergic and autoimmune diseases urges clinicians and researchers to search for new and efficient treatments. Strategies that activate antigen-specific immune tolerance and simultaneously maintain immune reactivity to all other antigens deserve special attention. Accordingly, antigen-presenting cells (APCs) seem to be the best suited for orchestrating these mechanisms by directing T cell immune responses towards a tolerant subtype. Recent advances in understanding cell-to-cell communication via extracellular vesicles (EVs) make the latter promising candidates for reprogramming APCs towards a tolerant phenotype, and for mediating tolerogenic APC function. Thus, comprehensive studies have been undertaken to describe the interactions of APCs and EVs naturally occurring during immune tolerance induction, as well as to develop EV-based manoeuvres enabling the induction of immune tolerance in an antigen-specific manner. In this review, we summarize the findings of relevant studies, with a special emphasis on future perspectives on their translation to clinical practice.

Lactococcus lactis harbouring Ara h 2.02 alleviates allergen-specific Th2-associated responses in sensitized mice

AIM

To study the prophylactic effect of recombinant Lactococcus lactis (rLl) harbouring Ara h 2.02 peanut allergen, in sensitized and challenged mice.

METHODS AND RESULTS

Ara h 2.02 cDNA was cloned into pNZ8048 for heterologous expression in L. lactis. The purified recombinant allergen showed IgE binding comparable with native Ara h 2. Balb/c mice were fed with either recombinant (rLl), nonrecombinant L. lactis (Ll) or NaHCO₃ (Sham) prior to sensitization and challenged with rAra h 2.02, whereas the baseline group was only fed with Ll. Allergen-specific immunoglobulin and splenocyte cytokines responses were determined for each mouse. Mice fed with either Ll or rLl showed significant alleviation of IgE and IgG₁ compared to the Sham group. Despite no significant decrease in Th2 (IL-4, IL-13, IL-6) or increase in Th1 (IFN-γ) cytokines, both groups showed lower IL-10 level, while the IL-4 : IFN-γ ratio was significantly lower for rLl compared to Ll group.

CONCLUSIONS

Oral administration of rLl harbouring Ara h 2.02 demonstrated alleviation of Th2-associated responses in allergen-challenged mice and a possible added allergen-specific prophylactic effect.

SIGNIFICANCE AND IMPACT OF THE STUDY

Ara h 2.02 coupled with the intrinsic properties of probiotic L. lactis as a delivery vehicle can be explored for the development of a commercially scalable vaccine.

Mechanism(s) of prolonged attenuation of allergic responses after modulation of idiotypic regulatory network

BACKGROUND

We showed previously that allergic reactivity to ovalbumin (OVA) could be regulated in mice following perturbation of immune networks using combinations of an immune Ig along with anti-idiotypic Ig. We have explored features of this regulation including: its persistence after cessation of administration of combined Igs; the ability of heterologous Igs to produce immunoregulation; a role for Treg induction in regulation; and the ability to attenuate responses in mice pre-sensitized to an allergic stimulus.

METHODS

BALB/c mice were sensitized to OVA. Mice also received 5 weekly injections of immune Ig or anti-idiotype Ig (at separate sites) from either homologous (mouse) or heterologous (human) sources. In the latter case pooled IVIG (given IM, hence hereafter IMIG) was used as a source of anti-idiotype Ig, and human anti-Tet as immune Ig. Injections of the Ig were given from the time of OVA sensitization (to attenuate development of immunity), or after pre-sensitization of mice (to attenuate existing allergic responses). All mice were assayed for development of OVA-specific serum IgE and IgG, as well as the production of OVA-induced IL-2, IL-4, IL-13, IL-31 and IL-33 in splenocytes cultured for 72 h. In studies examining possible mechanism(s) responsible for inhibition of immunity mice received, in addition to the Ig treatments described, infusion of depleting anti-CD4, and/or anti-CD8 antibodies, or a mAb to TNFSFR25, known to expand Tregs implicated in regulation of Allo immunity.

RESULTS

Combinations of both heterologous and homologous immune Igs and anti-idiotype Igs attenuated OVA allergic responses in both naïve and pre-sensitized mice. This attenuation persisted in mice greater than 14 weeks after cessation of treatment with the Igs used. Finally, depletion of either CD4 or CD8 cells ameliorated the suppressive effect seen, while the combination of anti-CD4 and anti-CD8 essentially abolished suppression. Suppression was further enhanced by anti-TNFSFR25 mAb.

CONCLUSIONS

We conclude that the combine Ig treatment protocols used produced a long-lasting suppression of allergic immunity, even in pre-sensitized animals. The effects seem to depend upon induction and expansion of Tregs and represents a novel approach to treatment of allergic disease in humans and other animals.

Il-10 producing T and B cells in allergy

The molecular and cellular mechanisms of allergen tolerance in humans have been intensively studied in the past few decades. The demonstration of epitope-specific T cell tolerance, particularly mediated by the immune suppressor functions of IL-10 led to a major conceptual change in this area more than 20 years ago. Currently, the known essential components of allergen tolerance include the induction of allergen-specific regulatory of T and B cells, the immune suppressive function of secreted factors, such as IL-10, IL-35, IL-1 receptor antagonist and TGF-β, immune suppressive functions of surface molecules such as CTLA-4 and PD-1, the production IgG4 isotype allergen-specific blocking antibodies, and decreased allergic inflammatory responses by mast cells, basophils, and eosinophils in inflamed tissues. In this review, we explain the importance of the role of IL-10 in allergen tolerance.

Mechanisms of Subcutaneous and Sublingual Aeroallergen Immunotherapy: What Is New?

Allergen immunotherapy (AIT) is considered to be the only treatment option with the promise of healing and induction of long-lasting allergen tolerance, persisting even after discontinuation of therapy. Despite a more than 100-year-long history, still only a minority of patients are being treated with AIT. Substantial developments took place in the last decade to overcome problems in standardization, efficacy, safety, high costs, long duration of treatment; and new guidelines have also been implemented. Major advancements in the understanding of AIT mechanisms with the focus on recent findings of subcutaneous and sublingual AIT have been summarized.

The use of biologics for immune modulation in allergic disease

The rising prevalence of allergies represents an increasing socioeconomic burden. A detailed understanding of the immunological mechanisms that underlie the development of allergic disease, as well as the processes that drive immune tolerance to allergens, will be instrumental in designing therapeutic strategies to treat and prevent allergic disease. Improved characterization of individual patients through the use of specific biomarkers and improved definitions of disease endotypes are paving the way for the use of targeted therapeutic approaches for personalized treatment. Allergen-specific immunotherapy and biologic therapies that target key molecules driving the Th2 response are already used in the clinic, and a wave of novel drug candidates are under development. In-depth analysis of the cells and tissues of patients treated with such targeted interventions provides a wealth of information on the mechanisms that drive allergies and tolerance to allergens. Here, we aim to deliver an overview of the current state of specific inhibitors used in the treatment of allergy, with a particular focus on asthma and atopic dermatitis, and provide insights into the roles of these molecules in immunological mechanisms of allergic disease.

Low Expression of IL-10 in Circulating Bregs and Inverted IL-10/TNF-α Ratio in Tears of Patients with Perennial Allergic Conjunctivitis: A Preliminary Study

Allergic conjunctivitis (AC) is one of the most common ophthalmological disorders seen in clinical practice. Growing evidence from recent years suggests that a subset of IL-10-expressing B cells is involved in inflammatory allergic diseases. In this study, we aimed to evaluate the potential involvement of blood Bregs cells in perennial allergic conjunctivitis (PAC), and interleukins (IL)-1β, IL-6, IL-8, IL-10, and IL-12, and tumor necrosis factor (TNF)-α, were measured in tear samples and compared with healthy controls (HC) using flow cytometry. Non-significant differences in CD19⁺IL-10⁺ cell frequency between PAC patients and healthy controls (HC) were observed. Nevertheless, when we analyzed the mean fluorescence intensity (MFI) of IL-10 on CD19⁺CD38^Lo/Med/Hi-gated cells, we observed a significant decrease in MFI in all Bregs subsets in PAC patients. Additionally, tear cytokines showed 2.8 times lower levels of IL-10 than TNF-α in PAC patients when compared to HC. Our findings demonstrate an immunological dysregulation in patients with allergic conjunctivitis, characterized by the low expression of IL-10 in circulating CD19⁺CD38⁺ Bregs subsets and an inverted tear IL-10/TNF-α ratio, promoting a local pro-inflammatory microenvironment. These findings highlight the novel pathologic changes involved in ocular allergic diseases. Understanding systemic and local mechanisms will aid the design of immunomodulating therapeutics at different levels.

Regulatory B and T lymphocytes in multiple sclerosis: friends or foes?

Current clinical experience with immunomodulatory agents and monoclonal antibodies in principle has established the benefit of depleting lymphocytic populations in relapsing–remitting multiple sclerosis (RRMS). B and T cells may exert multiple pro-inflammatory actions, but also possess regulatory functions making their role in RRMS pathogenesis much more complex. There is no clear correlation of Tregs and Bregs with clinical features of the disease. Herein, we discuss the emerging data on regulatory T and B cell subset distributions in MS and their roles in the pathophysiology of MS and its murine model, experimental autoimmune encephalomyelitis (EAE). In addition, we summarize the immunomodulatory properties of certain MS therapeutic agents through their effect on such regulatory cell subsets and their relevance to clinical outcomes.

Unstimulated Adult Human B Cells Include an IL-10+ Population with Suppressive Properties and an Activated Phenotype

B cells with regulatory properties have been recently identified and described in different immune disorders, including autoimmunity, infection, cancer, and allergy. in vitro studies of regulatory B cells are usually performed following prolonged cell culture and stimulation in order to obtain B cells capable of IL-10 secretion. We describe the isolation of viable IL-10-positive B cells directly from ex vivo unstimulated samples using the IL-10 secretion assay from Miltenyi Biotec, which was originally designed for IL-10-positive T cell analysis and isolation. IL-10-positive B cells from unstimulated samples represented approximately 2% of all B cells in healthy individuals, suppressed T cell proliferation and were enriched for surface markers of B cell activation. This tool has a potential to boost functional studies of IL-10-secreting B cells in health and disease. © 2018 International Society for Advancement of Cytometry.

The Multifaceted B Cell Response in Allergen Immunotherapy

While allergen immunotherapy (AIT) for IgE-mediated diseases holds curative potential, the considerable heterogeneity in clinical outcomes may relate to the complex mechanisms of tolerance. The regulation of humoral immunity by AIT contributes to the suppression of allergic responses. Recent findings have revealed novel roles for IgA and IgG antibodies in the induction of tolerance. These mechanisms synergize with their ability to block allergen-IgE binding and mediate inhibitory signaling of effector cells of the allergic response. In addition, the regulatory activity of B cells in AIT extends beyond IL-10 secretion and induction of IgG₄. Here, we review the evolution of the B cell response during AIT with special emphasis on the novel protective mechanisms entailing humoral immunity.

Differential Influence on Regulatory B Cells by TH2 Cytokines Affects Protection in Allergic Airway Disease

The role of regulatory B cells (Bregs) in modulating immune responses and maintaining tolerance are well established. However, how cytokines present during immune responses affect Breg growth and function are not as well defined. Previously, our laboratory reported IL-5- and mCD40L-expressing fibroblast (mCD40L-Fb) stimulation induced IL-10 production from murine B cells. The current study investigated the phenotype and functional relevance of IL-10- producing B cells from this culture. We found IL-5/mCD40L-Fb stimulation induced IL-10 production exclusively from CD5⁺ splenic B cells of naive mice. After stimulation, the resulting IL-10⁺ B cells displayed markers of multiple reported Breg phenotypes. Interestingly, when investigating effects of IL-4 (a critical T_H2 cytokine) on IL-5/mCD40L-Fb-induced IL-10 production, we found IL-4 inhibited IL-10 production in a STAT6-dependent manner. Upon adoptive transfer, CD5⁺ B cells previously stimulated with IL-5/mCD40L-Fb were able to reduce development of OVA-induced allergic airway disease in mice. Using B cells from IL-10 mutant mice differentiated by IL-5/mCD40L-Fb, we found protection from allergic airway disease development was dependent on the IL-10 production from the transferred B cells. Bregs have been shown to play crucial roles in the immune tolerance network, and understanding stimuli that modulate their growth and function may be key in development of future treatments for diseases of immune dysregulation.

Immunological Mechanisms in Allergic Diseases and Allergen Tolerance: The Role of Treg Cells

The immune system regulates itself to establish an appropriate immune response to potentially harmful pathogens while tolerating harmless environmental antigens and self-antigens. A central role in this balance is played by regulatory T cells (Tregs) through various ways of actions. By means of molecule secretion and cell-cell contact mechanisms, Tregs may have the capacity to modulate effector T cells and suppress the action of proinflammatory cytokines across a broad range of cell types. As a result, abnormal regulatory T cell function has been pointed as a main cause in the development of allergic diseases, a major public health problem in industrialized countries, with a high socioeconomic impact. This prevalence and impact have created an international interest in improving the allergy diagnosis and therapy. Additionally, research has sought to gain a better understanding of the molecular mechanisms underlining this kind of disease, in order to a better management. At this respect, the role of Treg cells is one of the most promising areas of research, mainly because of their potential use as new immunotherapeutical approaches. Therefore, the aim of this review is to update the existing knowledge of the role of Tregs in this pathology deepening in their implication in allergen-specific therapy (AIT).