IgE responses in mouse and man and the persistence of IgE memory

Staphylococcus aureus lysate induces an IgE response via memory B cells in nasal polyps

BACKGROUND

Locally increased IgE levels plays a pathologic role in chronic rhinosinusitis with nasal polyps (CRSwNP).

OBJECTIVE

This study aimed to investigate whether Staphylococcus aureus could induce aberrant IgE synthesis in CRSwNP and the potential mechanisms involved.

METHODS

Total IgE, IL-4, IL-5, and IL-13 concentrations in the supernatants of the cultures stimulated with S aureus lysate were assessed by ELISA. S aureus-induced cellular responses were investigated by single-cell RNA sequencing. Flow cytometry and quantitative reverse transcription PCR were used to analyze B-cell subsets and stimulated cell ε-germline transcript expression, respectively. IgE-positive B-cell and germinal center localization were assessed by immunohistochemistry and immunofluorescence.

RESULTS

S aureus lysate induced IgE production in the supernatants of nasal polyp (NP) tissues but not in those of healthy nasal mucosa. Moreover, IgE levels increased from days 2 to 4 after stimulation, paralleling the enhanced ε-germline transcript, IL-5, and IL-13 expression. Single-cell RNA sequencing revealed that there were increased IL-5 and IL-13 in group 2 innate lymphoid cells and identified a clonal overlap between unstimulated memory B cells and S aureus-stimulated plasma cells. The enriched IgE within NPs was mainly produced by IgE-negative memory B cells. Cellular evidence indicated that the IgE memory response to S aureus might also exist in the peripheral blood of CRSwNP patients. The S aureus-induced IgE memory response was associated with elevated IgE levels in NPs, asthma, and postoperative CRSwNP recurrence.

CONCLUSIONS

S aureus induced an IgE response via IgE-negative memory B cells in CRSwNP patients, possibly contributing to CRSwNP development.

A therapeutic strategy to target distinct sources of IgE and durably reverse allergy

Immunoglobulin E (IgE) is a key driver of type 1 hypersensitivity reactions and allergic disorders, which are globally increasing in number and severity. Although eliminating pathogenic IgE may be a powerful way to treat allergy, no therapeutic strategy reported to date can fully ablate IgE production. Interleukin-4 receptor α (IL-4Rα) signaling is required for IgE class switching, and IL-4Rα blockade gradually reduces, but does not eliminate, IgE. The persistence of IgE after IL-4Rα blockade may be due to long-lived IgE+ plasma cells that maintain serological memory to allergens and thus may be susceptible to plasma cell-targeted therapeutics. We demonstrate that transient administration of a B cell maturation antigen x CD3 (BCMAxCD3) bispecific antibody markedly depletes IgE, as well as other immunoglobulins, by ablating long-lived plasma cells, although IgE and other immunoglobulins rapidly rebound after treatment. Concomitant IL-4Rα blockade specifically and durably prevents the reemergence of IgE by blocking IgE class switching while allowing the restoration of other immunoglobulins. Moreover, this combination treatment prevented anaphylaxis in mice. Together with additional cynomolgus monkey and human data, our studies demonstrate that allergic memory is primarily maintained by both non-IgE+ memory B cells that require class switching and long-lived IgE+ plasma cells. Our combination approach to durably eliminate pathogenic IgE has potential to benefit allergy in humans while preserving antibody-mediated immunity.

We are memory: B-cell responses in allergy and tolerance

The significance of B-cell memory in sustaining IgE-mediated allergies but also ensuring the development of long-term allergen tolerance has remained enigmatic. However, well-thought murine and human studies have begun to shed more light on this highly disputed subject. The present mini review highlights important aspects, like the involvement of IgG1 memory B cells, the meaning of low- or high-affinity IgE antibody production, the impact of allergen immunotherapy, or the relevance of local memory established by ectopic lymphoid structures. Based on recent findings, future investigations should lead to deeper knowledge and the development of improved therapies treating allergic individuals.

Recombinant T-cell epitope conjugation: A new approach for Dermatophagoides hypoallergen design

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only clinical approach that can potentially cure some allergic diseases by inducing immunological tolerance. Dermatophagoides pteronyssinus is considered as the most important source of mite allergens worldwide, with high sensitization rates for the major allergens Der p 1, Der p 2 and Der p 23. The aim of this work is to generate a hypoallergenic hybrid molecule containing T-cell epitopes from these three major allergens.

METHODS

The hybrid protein termed Der p 2231 containing T-cell epitopes was purified by affinity chromatography. The human IgE reactivity was verified by comparing those with the parental allergens. The hybrid was also characterized immunologically through an in vivo mice model.

RESULTS

The hybrid rDer p 2231 stimulated in peripheral blood mononuclear cells (PBMCs) isolated from allergic patients with higher levels of IL- 2, IL-10, IL-15 and IFN-γ, as well as lower levels of IL-4, IL-5, IL-13, TNF-α and GM-CSF. The use of hybrid molecules as a therapeutic model in D. pteronyssinus allergic mice led to the reduction of IgE production and lower eosinophilic peroxidase activity in the airways. We found increased levels of IgG antibodies that blocked the IgE binding to the parental allergens in the serum of allergic patients. Furthermore, the stimulation of splenocytes from mice treated with rDer p 2231 induced higher levels of IL-10 and IFN-γ and decreased the secretion of IL-4 and IL-5, when compared with parental allergens and D. pteronyssinus extract.

CONCLUSIONS

rDer p 2231 has the potential to be used in AIT in patients co-sensitized with D. pteronyssinus major allergens, once it was able to reduce IgE production, inducing allergen-specific blocking antibodies, restoring and balancing Th1/Th2 immune responses, and inducing regulatory T-cells.

Development of allergen-specific IgE in a food-allergy model requires precisely timed B cell stimulation and is inhibited by Fgl2

Immunoglobulin E (IgE) responses are a central feature of allergic disease. Using a well-established food-allergy model in mice, we show that two sensitizations with cognate B cell antigen (Ag) and adjuvant 7 days apart promotes optimal development of IgE+ germinal center (GC) B cells and high-affinity IgE production. Intervals of 3 or 14 days between Ag sensitizations lead to loss of IgE+ GC B cells and an undetectable IgE response. The immunosuppressive factors Fgl2 and CD39 are down-regulated in T follicular helper (TFH) cells under optimal IgE-sensitization conditions. Deletion of Fgl2 in TFH and T follicular regulatory (TFR) cells, but not from TFR cells alone, increase Ag-specific IgE levels and IgE-mediated anaphylactic responses. Overall, we find that Ag-specific IgE responses require precisely timed stimulation of IgE+ GC B cells by Ag. Furthermore, we show that Fgl2 is expressed by TFH cells and represses IgE. This work has implications for the development and treatment of food allergies.

Using a mouse food-allergy model, Chen et al. find that allergen-specific IgE responses require precisely timed stimulation of IgE+ germinal center B cells. The authors further show that Fgl2 expressed by T follicular helper cells represses IgE. This work has implications for the development and treatment of food allergy.

Short- and Long-Lived Autoantibody-Secreting Cells in Autoimmune Neurological Disorders

As B cells differentiate into antibody-secreting cells (ASCs), short-lived plasmablasts (SLPBs) are produced by a primary extrafollicular response, followed by the generation of memory B cells and long-lived plasma cells (LLPCs) in germinal centers (GCs). Generation of IgG4 antibodies is T helper type 2 (Th2) and IL-4, -13, and -10-driven and can occur parallel to IgE, in response to chronic stimulation by allergens and helminths. Although IgG4 antibodies are non-crosslinking and have limited ability to mobilize complement and cellular cytotoxicity, when self-tolerance is lost, they can disrupt ligand-receptor binding and cause a wide range of autoimmune disorders including neurological autoimmunity. In myasthenia gravis with predominantly IgG4 autoantibodies against muscle-specific kinase (MuSK), it has been observed that one-time CD20⁺ B cell depletion with rituximab commonly leads to long-term remission and a marked reduction in autoantibody titer, pointing to a short-lived nature of autoantibody-secreting cells. This is also observed in other predominantly IgG4 autoantibody-mediated neurological disorders, such as chronic inflammatory demyelinating polyneuropathy and autoimmune encephalitis with autoantibodies against the Ranvier paranode and juxtaparanode, respectively, and extends beyond neurological autoimmunity as well. Although IgG1 autoantibody-mediated neurological disorders can also respond well to rituximab induction therapy in combination with an autoantibody titer drop, remission tends to be less long-lasting and cases where titers are refractory tend to occur more often than in IgG4 autoimmunity. Moreover, presence of GC-like structures in the thymus of myasthenic patients with predominantly IgG1 autoantibodies against the acetylcholine receptor and in ovarian teratomas of autoimmune encephalitis patients with predominantly IgG1 autoantibodies against the N‐methyl‐d‐aspartate receptor (NMDAR) confers increased the ability to generate LLPCs. Here, we review available information on the short-and long-lived nature of ASCs in IgG1 and IgG4 autoantibody-mediated neurological disorders and highlight common mechanisms as well as differences, all of which can inform therapeutic strategies and personalized medical approaches.

Study of selective immunoglobulin A deficiency among Egyptian patients with food allergy

Introduction

IgA deficiency is one of the commonest primary antibody deficiencies. Although many affected individuals could be asymptomatic, selected patients suffer from recurrent mucosal infections, allergies, and autoimmune diseases.

Aim of the study

To investigate the prevalence of IgA deficiency among Egyptian patients with food allergy.

Material and methods

We studied 100 patients (62 males, 38 females; mean age, 28.6 years) with multiple food allergies who were recruited on the basis of adequate immunological assessment by history, skin prick test, and confirmed by open challenge test as well as 50 healthy controls. Measurement of levels of IgE and IgA using ELISA technique were performed for all patients and controls.

Results

Deficiency of IgA was detected in 67% of patients with food allergy. Serum IgA levels were significantly lower among patients with food allergy (67.3 µg/ml; range, 56.7-72.0 µg/ml) as compared to healthy control (78.6 µg/ml; range, 72.8-84 µg/ml). Both IgA and IgE levels were not statistically different between patients with food allergy only and those with combined food and aeroallergen. Among food allergic group, serum IgA levels were inversely correlated with serum IgE levels (r = –0.314, p < 0.001).

Conclusions

Manifestations of atopy, such as food allergy might be a present feature before diagnosis of primary immune deficiency diseases as IgA deficiency.

Deletion of IL-4Rα signaling on B cells limits hyperresponsiveness depending on antigen load

BACKGROUND

B cells play an important role in allergies through secretion of IgE. IL-4 receptor α (IL-4Rα) is key in allergic asthma and regulates type 2 cytokine production, IgE secretion, and airway hyperresponsiveness. IL-4 activation of B cells is essential for class switching and contributes to the induction of B effector 2 (Be2) cells. The role of Be2 cells and signaling via IL-4Rα in B cells is not clearly defined.

OBJECTIVE

We sought to find out whether IL-4Rα-responsive B cells or Be2 function was essential in experimental allergic asthma.

METHODS

Mice lacking IL-4Rα on B cells (mb1^creIL-4Rα^-/lox) or littermate controls (IL-4Rα^-/lox) and mice lacking IL-4 or IL-4/IL-13 on B cells were sensitized and challenged with high-dose house dust mite (>10 μg) or with low-dose house dust mite (<3 μg). We also adoptively transferred naive IL-4Rα^-/lox or IL-4Rα^-/- B cells into μMT^-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness.

RESULTS

We found that IL-4Rα signaling on B cells was important for optimal T_H2 allergic immune responses mainly when the load of antigen is limited. IL-4Rα signaling on B cells was essential for germinal centers and in the effector phase of allergic responses. Be2 cells were essential in airway hyperresponsiveness, but not in other parameters.

CONCLUSIONS

IL-4Rα signaling on B cells is deleterious in allergic asthma because it is required for optimal T_H2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.

IgE and mast cells: The endogenous adjuvant

Mast cells and IgE are most familiar as the effectors of type I hypersensitivity reactions including anaphylaxis. It is becoming clear however that this pair has important immunomodulatory effects on innate and adaptive cells of the immune system. In this purview, they act as endogenous adjuvants to ignite evolving immune responses, promote the transition of allergic disease into chronic illness and disrupt the development of active mechanisms of tolerance to ingested foods. Suppression of IgE-mediated mast cell activation can be exerted by molecules targeting IgE, FcɛRI or signaling kinases including Syk, or by IgG antibodies acting via inhibitory Fcγ receptors. In 2015 we reviewed the evidence for the adjuvant functions of mast cells. This update includes the original text, incorporates some important developments in the field over the past five years and discusses how interventions targeting these pathways might have promise in the development of strategies to treat allergic disease.

Chronic allergen exposure drives accumulation of long-lived IgE plasma cells in the bone marrow, giving rise to serological memory

Immunoglobulin E (IgE) plays an important role in allergic diseases. Nevertheless, the source of IgE serological memory remains controversial. We reexamined the mechanism of serological memory in allergy using a dual reporter system to track IgE⁺ plasma cells in mice. Short-term allergen exposure resulted in the generation of IgE⁺ plasma cells that resided mainly in secondary lymphoid organs and produced IgE that was unable to degranulate mast cells. In contrast, chronic allergen exposure led to the generation of long-lived IgE⁺ plasma cells that were primarily derived from sequential class switching of IgG1, accumulated in the bone marrow, and produced IgE capable of inducing anaphylaxis. IgE⁺ plasma cells were found in the bone marrow of human allergic, but not nonallergic donors, and allergen-specific IgE produced by these cells was able to induce mast cell degranulation when transferred to mice. These data demonstrate that long-lived IgE⁺ bone marrow plasma cells arise during chronic allergen exposure and establish serological memory in both mice and humans.

Mimicking Antigen-Driven Asthma in Rodent Models-How Close Can We Get?

Asthma is a heterogeneous disease with increasing prevalence worldwide characterized by chronic airway inflammation, increased mucus secretion and bronchial hyperresponsiveness. The phenotypic heterogeneity among asthmatic patients is accompanied by different endotypes, mainly Type 2 or non-Type 2. To investigate the pathomechanism of this complex disease many animal models have been developed, each trying to mimic specific aspects of the human disease. Rodents have classically been employed in animal models of asthma. The present review provides an overview of currently used Type 2 vs. non-Type 2 rodent asthma models, both acute and chronic. It further assesses the methods used to simulate disease development and exacerbations as well as to quantify allergic airway inflammation, including lung physiologic, cellular and molecular immunologic responses. Furthermore, the employment of genetically modified animals, which provide an in-depth understanding of the role of a variety of molecules, signaling pathways and receptors implicated in the development of this disease as well as humanized models of allergic inflammation, which have been recently developed to overcome differences between the rodent and human immune systems, are discussed. Nevertheless, differences between mice and humans should be carefully considered and limits of extrapolation should be wisely taken into account when translating experimental results into clinical use.

Associations of Th2, Th17, Treg cells, and IgA+ memory B cells with atopic disease in children: The Generation R Study

BACKGROUND

New insights into immune cells could contribute to treatment and monitoring of atopic disease. Because nongenetic factors shape the human immune system, we here studied these immune cells in a large cohort with atopic children with adjustment for prenatal and postnatal confounders.

METHODS

Information on atopic dermatitis, inhalant- and food-allergic sensitization, asthma lung function scores was obtained from 855 10-year-old children within the Generation R cohort. 11-color flow cytometry was performed to determine CD27⁺ and CD27^- IgG⁺ , IgE⁺ and IgA⁺ memory B cells, Th1, Th2, Th17, and Treg-memory cells from venous blood. Associations between any atopic disease, the individual atopic diseases, and immune cell numbers were determined.

RESULTS

Children with any atopic disease had higher Th2, Treg, Treg-memory, and CD27⁺ IgA⁺ memory B-cell numbers compared to children without atopic disease. When studying the individual diseases compared to children without the individual diseases, children with atopic dermatitis, inhalant-, and food-allergic sensitization had higher memory Treg cell numbers 12.3% (95% CI 4.2; 21.0), (11.1% (95% CI 3.0; 19.8), (23.7% (95% CI 7.9; 41.8), respectively. Children with food-allergic sensitization had higher total B and CD27⁺ IgA⁺ memory B-cell numbers (15.2% [95% CI 3.2; 28.7], 22.5% [95% CI 3.9; 44.3], respectively). No associations were observed between asthma and B- or T-cell numbers.

CONCLUSION

Children with any atopic disease and children with inhalant- and food-allergic sensitization or atopic dermatitis had higher circulating memory Treg cells, but not higher IgE⁺ B-cell numbers. The associations of higher Treg and CD27⁺ IgA⁺ B-cell numbers in children with food-allergic sensitization are suggestive of TGF-β-mediated compensation for chronic inflammation.

Anaphylaxis for Internists: Definition, Evaluation, and Management, with a Focus on Commonly Encountered Problems

Anaphylaxis is an acute systemic allergic reaction that can be life threatening. In adults, the most common causes of anaphylaxis are foods, drugs, and insect stings. This article reviews the definition, classification, evaluation, differential diagnosis, prognosis, complications, and management of anaphylaxis. Tailored for internists, the article focuses on anaphylactic medication allergies. It provides a guide to optimally evaluate and manage patients with antibiotic allergy using a simple, rapid risk stratification technique, graded antibiotic challenge (test dose), and/or allergist-guided drug desensitization. It also reviews other causes of anaphylaxis that internists are likely to encounter, and an approach to their management.

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses

BACKGROUND

IgE is the least abundant immunoglobulin and tightly regulated, and IgE-producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood.

OBJECTIVE

The cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT) were investigated.

METHODS

In a randomized double-blind, placebo-controlled, time course SLIT study, PBMCs and nasal biopsy samples were collected from 40 adults with seasonal allergic rhinitis at baseline and at 4, 8, 16, 28, and 52 weeks. RNA was extracted from PBMCs, sorted B cells, and nasal biopsy samples for heavy chain variable gene repertoire sequencing. Moreover, mAbs were derived from single B-cell transcriptomes.

RESULTS

Combining heavy chain variable gene repertoire sequencing and single-cell transcriptomics yielded direct evidence of a parallel boost of 2 clonally and functionally related B-cell subsets of short-lived IgE⁺ plasmablasts and IgG⁺ memory B cells. Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgG_E repertoires. These were extensively mutated and appeared relatively stable as per heavy chain isotype, somatic hypermutations, and clonal composition. Single IgG_E⁺ memory B-cell and IgE⁺ preplasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and able to elicit basophil activation at very low allergen concentrations.

CONCLUSION

For the first time, we have shown that on mucosal allergen exposure, human IgE memory resides in allergen-specific IgG⁺ memory B cells. These cells rapidly switch isotype, expand into short-lived IgE⁺ plasmablasts, and serve as a potential target for therapeutic intervention.

Preventive effects of "ovalbumin-conjugated celastrol-loaded nanomicelles'' in a mouse model of ovalbumin-induced allergic airway inflammation

Allergies affect a significant proportion of the world's population, and existing vaccination strategies to restrict their adverse pathologies often render side-effects. The aim of this study was to design a new vaccine for allergen-specific immunotherapy (SIT), and to investigate its preventive effects during allergic inflammation. We constructed ovalbumin (OVA)-conjugated celastrol-loaded nanomicelles (OVA-NMs-celastrol), wherein celastrol (a bioactive anti-inflammatory compound) was loaded into carboxyl-functioned polymeric nanomicelles using a thin-film hydration method. OVA was used as a model allergen and conjugated on nanomicelles. The OVA-NMs-celastrol obtained were characterized based on particle size, morphology, drug encapsulation efficiency, and drug loading percentage. Further, the preventive effect of OVA-NMs-celastrol was evaluated in a mouse model of allergic asthma. Our results showed that OVA-NMs-celastrol possessed valuable characteristics such as small particle size (50.72 ± 0.98 nm) and spherical-like shape, with celastrol encapsulation efficiency of 99.89 ± 0.85% and a drug loading percentage of 4.76 ± 0.03%. Further, in vivo results showed that treatment with OVA-NMs-celastrol could decrease OVA specific IgE and histamine levels, Th2 cytokine (IL-4, IL-5) levels, and inflammatory cell infiltration in the lung tissues. Moreover, it could enhance the OVA specific IgG1 and IgG2a levels and decrease the IgE / IgG2a ratio. These results demonstrate the successful construction of OVA-NMs-celastrol as a potential vaccine candidate for use in SIT for allergic inflammation.

The Intersection of IgE Autoantibodies and Eosinophilia in the Pathogenesis of Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized by autoantibodies targeting cellular adhesion molecules. While IgE autoantibodies are occasionally reported in other autoimmune blistering diseases, BP is unique in that most BP patients develop an IgE autoantibody response. It is not known why BP patients develop self-reactive IgE and the precise role of IgE in BP pathogenesis is not fully understood. However, clinical evidence suggests an association between elevated IgE antibodies and eosinophilia in BP patients. Since eosinophils are multipotent effector cells, capable cytotoxicity and immune modulation, the putative interaction between IgE and eosinophils is a primary focus in current studies aimed at understanding the key components of disease pathogenesis. In this review, we provide an overview of BP pathogenesis, highlighting clinical and experimental evidence supporting central roles for IgE and eosinophils as independent mediators of disease and via their interaction. Additionally, therapeutics targeting IgE, the Th2 axis, or eosinophils are also discussed.

Species Specificity on Interaction between IgE and FcεRI

Allergic diseases are one of the most prevalent diseases at present, it is imperative to understanding the pathophysiology and treatment strategies for allergic diseases. In this process, the binding of IgE and FcεRI on effector cells plays a critical role in triggering allergic reactions. However, the species specificity of the interaction between IgE and FcεRI has not been clearly explained. This review described the characteristics and the interaction mechanism in the allergic reaction of IgE and FcεRI and summarized the species specificity between IgE and FcεRI.

Serum leptin levels correlate negatively with the capacity of vitamin D to modulate the in vitro cytokines production by CD4+ T cells in asthmatic patients

Both obesity and low vitamin D levels have been associated with allergic asthma (AA) severity. In the present study, severity of AA was associated with obesity but to the in vitro IgE production. In those patients, higher levels of IL-5, IL-6 and IL-17 were quantified in CD4⁺ T-cell cultures as compared with patients with mild and moderate AA. In addition, the lowest IL-10 levels were detected in the cell cultures from patients with a worse prognosis. Interestingly, the occurrence of AA elevates the plasma levels of leptin, and this adipokine was positively correlated with the release of IL-5, IL-6 and IL-17, but inversely correlated with IL-10 production, by CD4⁺ T-cells from patients. In AA-derived CD4⁺ T-cell cultures, 1,25(OH)2D3 was less efficient at inhibiting IL-5, IL-6 and IL-17 production, and up regulating IL-10 release, as those from healthy subjects. Interestingly, the in vitro immunomodulatory effects of vitamin D were inversely correlated with serum leptin levels. In summary, our findings suggested that obesity, probably due to the overproduction of leptin, negatively impacts AA as it favors imbalance between Th2/Th17 and regulatory phenotypes. The deleterious effects of leptin may also be due to its ability to counter-regulate the immunosuppressive effects of vitamin D.

Transcriptional Analysis of the Human IgE-Expressing Plasma Cell Differentiation Pathway

IgE is secreted by plasma cells (PCs) and is central to allergic disease. Using an ex vivo tonsil B cell culture system, which mimics the Th2 responses in vivo, we have recently characterized the development pathway of human IgE-expressing PCs. In this system, as in mice, we reported the predisposition of IgE-expressing B cells to differentiate into PCs. To gain a comprehensive understanding of the molecular events involved in the differentiation of human IgE⁺ B cells into PCs we have used the Illumina HumanHT-12 v4 Expression BeadChip array to analyse the gene expression profile of ex vivo generated human IgE⁺ B cells at various stages of their differentiation into PCs. We also compared the transcription profiles of IgE⁺ and IgG1⁺ cells to discover isotype-specific patterns. Comparisons of IgE⁺ and IgG1⁺ cell transcriptional profiles revealed molecular signatures specific for IgE⁺ cells, which diverge from their IgG1⁺ cell counterparts upon differentiation into PCs. At the germinal center (GC) stage of development, unlike in some mouse studies of IgE biology, we observed similar rates of apoptosis and no significant differences in the expression of apoptosis-associated genes between the IgE⁺ and IgG1⁺ B cells. We identified a gene interaction network associated with early growth response 1 (EGR1) that, together with the up-regulated IRF4, may account for the predisposition of IgE⁺ B cells to differentiate into PCs. However, despite their swifter rates of PC differentiation, the transcription profile of IgE⁺ PCs is more closely related to IgE⁺ and IgG1⁺ plasmablasts (PBs) than to IgG1⁺ PCs, suggesting that the terminal differentiation of IgE⁺ cells is impeded. We also show that IgE⁺ PCs have increased levels of apoptosis suggesting that the IgE⁺ PCs generated in our in vitro tonsil B cell cultures, as in mice, are short-lived. We identified gene regulatory networks as well as cell cycle and apoptosis signatures that may explain the diverging PC differentiation programme of these cells. Overall, our study provides a detailed analysis of the transcriptional pathways underlying the differentiation of human IgE-expressing B cells and points to molecular signatures that regulate IgE⁺ PC differentiation and function.

Gut Mucosal Antibody Responses and Implications for Food Allergy

The gastrointestinal mucosa is a critical environmental interface where plasma cells and B cells are exposed to orally-ingested antigens such as food allergen proteins. It is unclear how the development of B cells and plasma cells in the gastrointestinal mucosa differs between healthy humans and those with food allergy, and how B cells contribute to, or are affected by, the breakdown of oral tolerance. In particular, the antibody gene repertoires associated with symptomatic allergy have only begun to be characterized in full molecular detail. Here, we review literature concerning B cells and plasma cells in the gastrointestinal system in the context of food allergy, with a focus on human studies.

Nanoemulsion adjuvant-driven redirection of TH2 immunity inhibits allergic reactions in murine models of peanut allergy

BACKGROUND

Immunotherapy for food allergies involves progressive increased exposures to food that result in desensitization to food allergens in some subjects but not tolerance to the food. Therefore new approaches to suppress allergic immunity to food are necessary. Previously, we demonstrated that intranasal immunization with a nanoemulsion (NE) adjuvant induces robust mucosal antibody and T_H17-polarized immunity, as well as systemic T_H1-biased cellular immunity with suppression of pre-existing T_H2-biased immunity.

OBJECTIVE

We hypothesized that immunization with food in conjunction with the nanoemulsion adjuvant could lead to modulation of allergic reactions in food allergy by altering pre-existing allergic immunity and enhancing mucosal immunity.

METHODS

Mice were sensitized to peanut with aluminum hydroxide or cholera toxin. The animals were then administered 3 monthly intranasal immunizations with peanut in the nanoemulsion adjuvant or saline. Mice were then challenged with peanut to examine allergen reactivity.

RESULTS

The NE intranasal immunizations resulted in marked decreases in T_H2 cytokine, IgG₁, and IgE levels, whereas T_H1 and mucosal T_H17 immune responses were increased. After allergen challenge, these mice showed significant reductions in allergic hypersensitivity. Additionally, the NE immunizations significantly increased antigen-specific IL-10 production and regulatory T-cell counts, and the protection induced by NE was dependent in part on IL-10. Control animals immunized with intranasal peanut in saline had no modulation of their allergic response.

CONCLUSIONS

NE adjuvant-mediated induction of mucosal T_H17 and systemic T_H1-biased immunity can suppress T_H2-mediated allergy through multiple mechanisms and protect against anaphylaxis. These results suggest the potential therapeutic utility of this approach in the setting of food allergy.

Mechanisms of allergen immunotherapy for inhaled allergens and predictive biomarkers

Allergen immunotherapy is effective in patients with IgE-dependent allergic rhinitis and asthma. When immunotherapy is given continuously for 3 years, there is persistent clinical benefit for several years after its discontinuation. This disease-modifying effect is both antigen-specific and antigen-driven. Clinical improvement is accompanied by decreases in numbers of effector cells in target organs, including mast cells, basophils, eosinophils, and type 2 innate lymphoid cells. Immunotherapy results in the production of blocking IgG/IgG₄ antibodies that can inhibit IgE-dependent activation mediated through both high-affinity IgE receptors (FcεRI) on mast cells and basophils and low-affinity IgE receptors (FcεRII) on B cells. Suppression of T_H2 immunity can occur as a consequence of either deletion or anergy of antigen-specific T cells; induction of antigen-specific regulatory T cells; or immune deviation in favor of T_H1 responses. It is not clear whether the altered long-term memory resides within the T-cell or the B-cell compartment. Recent data highlight the role of IL-10-producing regulatory B cells and "protective" antibodies that likely contribute to long-term tolerance. Understanding mechanisms underlying induction and persistence of tolerance should identify predictive biomarkers of clinical response and discover novel and more effective strategies for immunotherapy.

Correlation between cell aggregation and antibody production in IgE-producing plasma cells

Allergic conditions result in the increase of immunoglobulin (Ig)E-producing plasma cells (IgE-PCs); however, it is unclear how IgE production is qualitatively controlled. In this study, we found that IgE-PCs in spleen of immunized mice formed homotypic cell aggregates. By employing IgE-producing hybridomas (IgE-hybridomas) as a model of IgE-PCs, we showed that these cells formed aggregates in the presence of specific antigens (Ags). The formation of the Ag-induced cell aggregation involved secreted IgE and Fcγ receptor (FcγR)II/FcγRIII, but not FcεRs. Ag-induced cell aggregation plus lipopolysaccharide signaling resulted in an enhancement of IgE production in aggregated IgE-hybridomas. Furthermore, the administration of anti-FcγRII/FcγRIII antagonistic monoclonal antibody to immunized mice tended to reduce the splenic IgE-PC aggregation as well as the serum IgE levels. Taken together, our results suggested that Ag-IgE complexes induced IgE-PCs aggregation via FcγRII/FcγRIII, leading to the enhancement of IgE production. These findings suggest the presence of a novel mechanism for regulation of IgE production.

Positive allergen reaction in allergic and nonallergic rhinitis: a systematic review

BACKGROUND

The diagnosis of allergic rhinitis (AR) is based on cutaneous and serological assessment to determine immunoglobulin E (IgE)-mediated disease. However, discrepancies between these tests and nasal provocation exist. Patients diagnosed as non-allergic rhinitis (NAR) but with positive nasal allergen provocation test (NAPT) may represent a local allergic condition or entopy, still suitable to allergy interventions. The objective of this study was to determine the frequency of nasal reactivity toward allergens among AR and NAR patients, and to describe the diagnostic characteristics of NAPT methodologies.

METHODS

EMBASE (1947-) and Medline (1946-) were searched until December 8, 2015. A search strategy was used to identify studies on AR or NAR patients subjected to diagnostic local nasal provocation. All studies providing original NAPT data among the AR or NAR population were included. Meta-analysis of proportion data was presented as a weighted probability % (95% confidence interval [CI]).

RESULTS

The search yielded 4504 studies and 46 were included. The probability of nasal allergen reactivity for the AR population was 86.3% (95% CI, 84.4 to 88.1) and in NAR was 24.7% (95% CI, 22.3 to 27.2). Reactivity was high with pollen for both AR 97.1% (95% CI, 94.2 to 99.2) and NAR 47.5% (95% CI, 34.8 to 60.4), and lowest with dust for both AR 79.1% (95% CI, 76.4 to 81.6) and NAR 12.2% (95% CI, 9.9 to 14.7). NAPT yielded high positivity when defined by subjective end-points: AR 91.0% (95% CI, 86.6 to 94.8) and NAR 30.2% (95% CI, 22.9 to 37.9); and lower with objective end-points: AR 80.8% (95% CI, 76.8 to 84.5) and NAR 14.1% (95% CI, 11.2 to 17.2).

CONCLUSION

Local allergen reactivity is demonstrated in 26.5% of patients previously considered non-allergic. Similarly, AR, when defined by skin-prick test (SPT) or serum specific IgE (sIgE), may lead to 13.7% of patients with inaccurate allergen sensitization or non-allergic etiologies.

BCG and protection against inflammatory and auto-immune diseases

INTRODUCTION

Bacillus Calmette-Guérin (BCG) is the only available vaccine against tuberculosis. Although its protective efficacy against pulmonary tuberculosis is still under debate, it provides protection against other mycobacterial diseases. BCG is also an effective therapy against superficial bladder cancer and potentially decreases overall childhood mortality. Areas covered: The purpose of this paper is to provide a state-of-the-art summary of the beneficial effects of BCG in inflammatory and auto-immune diseases. As a strong inducer of Th1 type immunity, BCG has been reported to protect against atopic conditions, such as allergic asthma, a Th2-driven disorder. Its protective effect has been well documented in mice, but still awaits definitive evidence in humans. Similarly, murine studies have shown a protective effect of BCG against auto-immune diseases, such as multiple sclerosis and insulin-dependent diabetes, but studies in humans have come to conflicting conclusions. Expert commentary: Studies in mice have shown a beneficial effect of the BCG vaccine against allergic asthma, multiple sclerosis and diabetes. However, the understanding of its mechanism is still fragmentary and requires further in depth research. Some observational or intervention studies in humans have also suggested a beneficial effect, but definitive evidence for this requires confirmation in carefully conducted prospective studies.

Nonallergic rhinitis and lower airway disease

In the past years, several investigators have demonstrated the existence of local nasal responses in some patients with typical allergic rhinitis symptoms but without atopy and have defined a new phenotype called local allergic rhinitis (LAR) or 'entopy'. In a percentage of LAR subjects, the upper airway disease is also associated with lower airway symptoms. After the description of this phenotype, the differential diagnosis between LAR and nonallergic rhinitis (NAR) has become a challenge for the clinician. To correctly identify LAR patients is of high importance for treatment and management of these patients, and for an appropriate inclusion of patients in clinical trials and genetics studies. The treatment of LAR patients, in contrast with NAR, is oriented to allergen avoidance and specific treatment. Allergen immunotherapy, the aetiological treatment for allergic respiratory diseases, has demonstrated to be an effective and safe treatment in LAR, increasing immunological tolerance, and reducing the clinical symptoms and the use of medication. In this article, the important and novel aspects of LAR in terms of mechanisms, diagnosis and treatment will be discussed. Also, the involvement of the lower airway and the potential role of IgE in the bronchial disease will be also reviewed.

Ontogeny of human IgE-expressing B cells and plasma cells

Background

IgE‐expressing (IgE⁺) plasma cells (PCs) provide a continuous source of allergen‐specific IgE that is central to allergic responses. The extreme sparsity of IgE⁺ cells in vivo has confined their study almost entirely to mouse models.

Objective

To characterize the development pathway of human IgE⁺PCs and to determine the ontogeny of human IgE⁺PCs.

Methods

To generate human IgE⁺ cells, we cultured tonsil B cells with IL‐4 and anti‐CD40. Using FACS and RT‐PCR, we examined the phenotype of generated IgE⁺ cells, the capacity of tonsil B‐cell subsets to generate IgE⁺PCs and the class switching pathways involved.

Results

We have identified three phenotypic stages of IgE⁺PC development pathway, namely (i) IgE⁺germinal centre (GC)‐like B cells, (ii) IgE⁺PC‐like ‘plasmablasts’ and (iii) IgE⁺PCs. The same phenotypic stages were also observed for IgG1⁺ cells. Total tonsil B cells give rise to IgE⁺PCs by direct and sequential switching, whereas the isolated GC B‐cell fraction, the main source of IgE⁺PCs, generates IgE⁺PCs by sequential switching. PC differentiation of IgE⁺ cells is accompanied by the down‐regulation of surface expression of the short form of membrane IgE (mIgE_S), which is homologous to mouse mIgE, and the up‐regulation of the long form of mIgE (mIgE_L), which is associated with an enhanced B‐cell survival and expressed in humans, but not in mice.

Conclusion

Generation of IgE⁺PCs from tonsil GC B cells occurs mainly via sequential switching from IgG. The mIgE_L/mIgE_S ratio may be implicated in survival of IgE⁺ B cells during PC differentiation and allergic disease.

Intrinsic transcriptional heterogeneity in B cells controls early class switching to IgE

Combining novel mouse reporters and single-cell transcriptomic analyses, Wu et al. uncover differential activation thresholds for the transcripts that direct antibody class switching to IgE versus IgG1 in response to IL-4 and explain how cell-intrinsic transcriptional heterogeneity governs CSR.

Noncoding transcripts originating upstream of the immunoglobulin constant region (I transcripts) are required to direct activation-induced deaminase to initiate class switching in B cells. Differential regulation of Iε and Iγ1 transcription in response to interleukin 4 (IL-4), hence class switching to IgE and IgG1, is not fully understood. In this study, we combine novel mouse reporters and single-cell RNA sequencing to reveal the heterogeneity in IL-4–induced I transcription. We identify an early population of cells expressing Iε but not Iγ1 and demonstrate that early Iε transcription leads to switching to IgE and occurs at lower activation levels than Iγ1. Our results reveal how probabilistic transcription with a lower activation threshold for Iε directs the early choice of IgE versus IgG1, a key physiological response against parasitic infestations and a mediator of allergy and asthma.

The Developmental History of IgE and IgG4 Antibodies in Relation to Atopy, Eosinophilic Esophagitis, and the Modified TH2 Response

A common reaction from anyone confronted with allergy is the question: what prevents universal allergy? We will discuss recent findings in the mouse system that have provided us with clues on why allergy is not more common. We will also address one crucial aspect of atopic allergy in humans, which is absent in most mouse model systems, an IgG/IgE ratio <10. We consider the typical mouse IgE response to be more closely related to the "modified TH2" response in humans. We will discuss the similarities and differences between the IgE and IgG4 response to allergens and an update on the IgG4 B cell, partly derived from studies on eosinophilic esophagitis and IgG4-related diseases.

Diagnostic Utility of Total IgE in Foods, Inhalant, and Multiple Allergies in Saudi Arabia

Objective. To assess the diagnostic significance of total IgE in foods, inhalant, and multiple allergies. Methods. Retrospective review of the laboratory records of patients who presented with clinical suspicion of food or inhalant allergy between January 2013 and December 2014. Total IgE level was defined as positive for a value >195 kU/L; and diagnosis was confirmed by the detection of specific IgE (golden standard) for at least one food or inhalant allergen and at least two allergens in multiple allergies. Results. A total of 1893 (male ratio = 0.68, mean age = 39.0 ± 19.2 years) patients were included. Total IgE had comparable sensitivity (55.8% versus 59.6%) and specificity (83.9% versus 84.4%) in food versus inhalant allergy, respectively, but a superior PPV in inhalant allergy (79.1% versus 54.4%). ROC curve analysis showed a better diagnostic value in inhalant allergies (AUC = 0.817 (95% CI = 0.796-0.837) versus 0.770 (95% CI = 0.707-0.833)). In multiple allergies, total IgE had a relatively good sensitivity (78.6%), while negative IgE testing (<195 kU/L) predicted the absence of multiple allergies with 91.5% certitude. Conclusion. Total IgE assay is not efficient as a diagnostic test for foods, inhalant, or multiple allergies. The best strategy should refer to specific IgE testing guided by a comprehensive atopic history.

Intrinsic properties of germinal center-derived B cells promote their enhanced class switching to IgE

BACKGROUND

Research on the origins and development of human IgE-expressing (IgE(+) ) cells is required for understanding the pathogenesis of allergy and asthma. These studies have been thwarted by the rarity of IgE(+) cells in vivo and the low frequency of class switch recombination (CSR) to IgE ex vivo. To determine the main source of IgE(+) cells, we investigated the relation between the phenotypic composition of tonsil B cells and the CSR to IgE ex vivo.

METHODS

Human tonsil B cells were analyzed by flow cytometry (FACS) and cultured with IL-4 and anti-CD40 to induce CSR to IgE. Naïve, germinal center (GC), early GC (eGC), and memory tonsil B cells were isolated by FACS, and their capacities for IL-4 and anti-CD40 signaling, cell proliferation, and de novo class switching to IgE were analyzed by RT-PCR and FACS.

RESULTS

B cells from different tonsils exhibited varying capacities for CSR to IgE ex vivo. This was correlated with the percentage of eGC B cells in the tonsil at the outset of the culture. Despite relatively poor cell viability, eGC and GC B-cell cultures produced the highest yields of IgE(+) cells compared to naïve and memory B-cell cultures. The main factors accounting for this result were the strength of IL-4R and CD40 signaling and relative rates of cell proliferation.

CONCLUSIONS

This study shows that the maturation state of tonsil B cells determines their capacity to undergo class switching to IgE ex vivo, with the GC-derived B cells yielding the highest percentage of IgE(+) cells.