Germinal center formation and local immunoglobulin E (IgE) production in the lung after an airway antigenic challenge

Decoding the genetic and epigenetic basis of asthma

Asthma is a complex and heterogeneous chronic inflammatory disease of the airways. Alongside environmental factors, asthma susceptibility is strongly influenced by genetics. Given its high prevalence and our incomplete understanding of the mechanisms underlying disease susceptibility, asthma is frequently studied in genome-wide association studies (GWAS), which have identified thousands of genetic variants associated with asthma development. Virtually all these genetic variants reside in non-coding genomic regions, which has obscured the functional impact of asthma-associated variants and their translation into disease-relevant mechanisms. Recent advances in genomics technology and epigenetics now offer methods to link genetic variants to gene regulatory elements embedded within non-coding regions, which have started to unravel the molecular mechanisms underlying the complex (epi)genetics of asthma. Here, we provide an integrated overview of (epi)genetic variants associated with asthma, focusing on efforts to link these disease associations to biological insight into asthma pathophysiology using state-of-the-art genomics methodology. Finally, we provide a perspective as to how decoding the genetic and epigenetic basis of asthma has the potential to transform clinical management of asthma and to predict the risk of asthma development.

Role of tertiary lymphoid organs in the regulation of immune responses in the periphery

Tertiary lymphoid organs (TLOs) are collections of immune cells resembling secondary lymphoid organs (SLOs) that form in peripheral, non-lymphoid tissues in response to local chronic inflammation. While their formation mimics embryologic lymphoid organogenesis, TLOs form after birth at ectopic sites in response to local inflammation resulting in their ability to mount diverse immune responses. The structure of TLOs can vary from clusters of B and T lymphocytes to highly organized structures with B and T lymphocyte compartments, germinal centers, and lymphatic vessels (LVs) and high endothelial venules (HEVs), allowing them to generate robust immune responses at sites of tissue injury. Although our understanding of the formation and function of these structures has improved greatly over the last 30 years, their role as mediators of protective or pathologic immune responses in certain chronic inflammatory diseases remains enigmatic and may differ based on the local tissue microenvironment in which they form. In this review, we highlight the role of TLOs in the regulation of immune responses in chronic infection, chronic inflammatory and autoimmune diseases, cancer, and solid organ transplantation.

CXCL13 is expressed in a subpopulation of neuroendocrine cells in the murine trachea and lung

The conducting airways are lined by distinct cell types, comprising basal, secretory, ciliated, and rare cells, including ionocytes, solitary cholinergic chemosensory cells, and solitary and clustered (neuroepithelial bodies) neuroendocrine cells. Airway neuroendocrine cells are in clinical focus since they can give rise to small cell lung cancer. They have been implicated in diverse functions including mechanosensation, chemosensation, and regeneration, and were recently identified as regulators of type 2 immune responses via the release of the neuropeptide calcitonin gene-related peptide (CGRP). We here assessed the expression of the chemokine CXCL13 (B cell attracting chemokine) by these cells by RT-PCR, in silico analysis of publicly available sequencing data sets, immunohistochemistry, and immuno-electron microscopy. We identify a phenotype of neuroendocrine cells in the naïve mouse, producing the chemokine CXCL13 predominantly in solitary neuroendocrine cells of the tracheal epithelium (approx. 70% CXCL13⁺) and, to a lesser extent, in the solitary neuroendocrine cells and neuroepithelial bodies of the intrapulmonary bronchial epithelium (< 10% CXCL13⁺). In silico analysis of published sequencing data of murine tracheal epithelial cells was consistent with the results obtained by immunohistochemistry as it revealed that neuroendocrine cells are the major source of Cxcl13-mRNA, which was expressed by 68–79% of neuroendocrine cells. An unbiased scRNA-seq data analysis of overall gene expression did not yield subclusters of neuroendocrine cells. Our observation demonstrates phenotypic heterogeneity of airway neuroendocrine cells and points towards a putative immunoregulatory role of these cells in bronchial-associated lymphoid tissue formation and B cell homeostasis.

Repeated exposure to inactivated Streptococcus pneumoniae induces asthma-like pathological changes in mice in the presence of IL-33

While environmental aeroallergens and epithelial alarmins such as IL-33 are firmly implicated in asthma, the possible role of Streptococcus pneumoniae (S. pneumoniae) antigens is less clear. To explore this, wild-type BALB/c mice were repeatedly challenged per-nasally with IL-33 and inactivated S. pneumoniae, either agent alone or diluent control. Some animals were rested then later re-challenged with inactivated S. pneumoniae alone. Serum concentrations of S. pneumoniae lysates-specific IgE were measured in patients with asthma and control subjects. Interestingly, in the presence of IL-33, repeated exposure to inactivated S. pneumoniae induced asthma-like pathological changes accompanied by a systemic adaptive immune response. Subsequent re-exposure of the sensitized animals to inactivated S. pneumoniae alone was able to induce such changes. The concentration of S. pneumoniae lysates-specific IgE was significantly elevated in the asthma patients. These data suggest that antigens derived from infectious microorganisms may participate in generating the mucosal inflammation which characterizes asthma.

Bronchus-Associated Lymphoid Tissue (BALT) Histology and Its Role in Various Pathologies

The lower respiratory tract is in direct communication with the external environment for gas exchange to occur. Therefore, it is constantly exposed to allergens, antigens, bacteria, viruses, and a wide variety of airborne foreign bodies. Bronchus-associated lymphoid tissue (BALT), which develops in response to these exposures and is one of the most prominent representatives of mucosa-associated lymphoid tissue (MALT), is important for generating rapid and specific bronchopulmonary adaptive immune responses. Therefore, this chapter focuses on the lymphoid architecture of BALT, which was first discovered in the bronchial wall of rabbits, its inducible form called inducible BALT (iBALT), its immunological response mechanisms, and its roles in certain pathologies including infectious and autoimmune diseases as well as in allergic and malignant conditions. In conclusion, it is hypothesized that BALT plays an important role in maintaining health and in the development of lower respiratory tract diseases; thanks to the pulmonary immune system in which it functions as a functional lymphoid tissue.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.

Regulatory and IgE+ B Cells in Allergic Asthma

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

Presence of Tertiary Lymphoid Organ in Nasal Inverted Papilloma Is Correlated with Eosinophil Infiltration and Local Immunoglobulin Production

INTRODUCTION

Nasal inverted papilloma (NIP) is a benign tumour with multiple inflammatory cell infiltration. Tertiary lymphoid organs (TLOs) support local antibody production and play important roles in airway inflammation. However, the evidence of TLOs and local immunoglobulins in NIP has not been reported yet. We investigated the presence of TLOs and immunoglobulins in NIP tissues and their association with the clinical-pathological characteristics of NIPs.

METHODS

We analyzed the occurrence and composition of TLOs and local immunoglobulins by immunohistochemistry and evaluated the lymph organogenesis associated genes and cytokines by quantitative qPCR and Luminex assays, respectively, in papilloma tissues from 84 NIP cases.

RESULTS

TLOs were present in 54% (45/84) of the NIP patients but not in control subjects. TLOs were composed of T cells, B cells, follicular dendritic cells, macrophages, and natural killer cells. Compared to NIP tissues without TLOs, tissues with TLOs showed significantly higher eosinophil infiltration levels (3.5-fold), elevation of lymphorganogenic genes (CXCL12, CXCL13, CCL20, CCL21, CD21L, and lymphotoxin alpha and beta), and increased Th17 (IL-21, IL-22, and GM-CSF) and Th2 (IL-5 and IL-13) cytokine production. Moreover, NIP with TLOs demonstrated a higher number of follicular T helper cells and immunoglobulin-producing plasma cells (CD138+ IgA+, CD138+ IgM+, CD138+ IgE+, and CD138+ IgG+) than those without TLOs, and these antibody-producing cells were positively correlated with the eosinophil number.

CONCLUSION

The high frequency of TLOs and excess local immunoglobulin production are associated with an eosinophilic and Th2 skew microenvironment in the NIP mucosa, which would contribute to an important immunopathogenic response during NIP pathogenesis.

Serum immunoglobulin E responses to aeroallergens in cats with naturally occurring airway eosinophilia compared to unaffected control cats

BACKGROUND

Eosinophilic airway disease in cats is sometimes described as allergic in origin, but controversy exists in the documentation of allergy in cats and the utility of allergy testing for respiratory tract diseases.

OBJECTIVE

To examine serum immunoglobulin E (IgE) response to aeroallergens in cats with airway eosinophilia.

ANIMALS

Fifteen cats with idiopathic eosinophilic airway inflammation and 9 control cats.

METHODS

Prospective, case-control study. Surplus serum from cats with airway eosinophilia documented by bronchoscopic bronchoalveolar lavage was submitted for IgE measurement using ELISA polyclonal antibody methodology. Responses for regional allergens (fungal organisms, weeds, grasses, trees, mites, insects) were assessed. Results were reported as ELISA absorbance units with scores 0 to 79 considered negative, scores between 80 and 300 considered intermediate, and scores >300 considered positive.

RESULTS

Cats with airway eosinophilia had significantly more positive serum IgE responses (25/720) than did healthy controls (5/432, P = .02); however, the number of cats with positive IgE responses (5/15) did not differ from controls (1/9, P = .35). The allergen that most commonly resulted in positive serum IgE response in cats with airway eosinophilia was dust mite (n = 4) followed by 2 types of storage mites (n = 3 each). No control cat tested positive for these allergens.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum IgE production against aeroallergens was found in some cats with eosinophilic airway inflammation, but the number of affected cats with positive results did not differ from controls. Further investigation in cats with eosinophilic, mixed, and neutrophilic airway disease in comparison to control cats is warranted.

Lung transcriptomic clock predicts premature aging in cigarette smoke-exposed mice

BACKGROUND

Lung aging is characterized by a number of structural alterations including fibrosis, chronic inflammation and the alteration of inflammatory cell composition. Chronic exposure to cigarette smoke (CS) is known to induce similar alterations and may contribute to premature lung aging. Additionally, aging and CS exposure are associated with transcriptional alterations in the lung. The current work aims to explore the interaction between age- and CS- associated transcriptomic perturbations and develop a transcriptomic clock able to predict the biological age and the impact of external factors on lung aging.

RESULTS

Our investigations revealed a substantial overlap between transcriptomic response to CS exposure and age-related transcriptomic alterations in the murine lung. Of particular interest is the strong upregulation of immunoglobulin genes with increased age and in response to CS exposure, indicating an important implication of B-cells in lung inflammation associated with aging and smoking. Furthermore, we used a machine learning approach based on Lasso regression to build a transcriptomic age model that can accurately predict chronological age in untreated mice and the deviations associated with certain exposures. Interestingly, CS-exposed-mice were predicted to be prematurely aged in contrast to mice exposed to fresh air or to heated tobacco products (HTPs). The accelerated aging rate associated with CS was reversed upon smoking cessation or switching to HTPs. Additionally, our model was able to predict premature aging associated with thoracic irradiation from an independent public dataset.

CONCLUSIONS

Aging and CS exposure share common transcriptional alteration patterns in the murine lung. The massive upregulation of B-cell restricted genes during these processes shed light on the contribution of cell composition and particularly immune cells to the measured transcriptomic signal. Through machine learning approach, we show that gene expression changes can be used to accurately monitor the biological age and the modulations associated with certain exposures. Our findings also suggest that the premature lung aging is reversible upon the reduction of harmful exposures.

Friend or Foe: The Protective and Pathological Roles of Inducible Bronchus-Associated Lymphoid Tissue in Pulmonary Diseases

Inducible bronchus-associated lymphoid tissue (iBALT) is a tertiary lymphoid structure that resembles secondary lymphoid organs. iBALT is induced in the lung in response to Ag exposure. In some cases, such as infection with Mycobacterium tuberculosis, the formation of iBALT structure is indicative of an effective protective immune response. However, with persistent exposure to Ags during chronic inflammation, allergy, or autoimmune diseases, iBALT may be associated with exacerbation of inflammation. iBALT is characterized by well-organized T and B areas enmeshed with conventional dendritic cells, follicular dendritic cells, and stromal cells, usually located surrounding airways or blood vessels. Several of the molecular signals and cellular contributors that mediate formation of iBALT structures have been recently identified. This review will outline the recent findings associated with the formation and maintenance of iBALT and their contributions toward a protective or pathogenic function in pulmonary disease outcome.

Immunological association of inducible bronchus-associated lymphoid tissue organogenesis in Ag85B-rHPIV2 vaccine-induced anti-tuberculosis mucosal immune responses in mice

We previously reported that Ag85B-expressing human parainfluenza type 2 virus (Ag85B-rHPIV2) was effective as a nasal vaccine against tuberculosis in mice; however, the mechanism by which it induces an immune response remains to be investigated. In the present study, we found that organogenesis of inducible bronchus-associated lymphoid tissue (iBALT) played a role in the induction of antigen-specific T cells and IgA antibody responses in the lung of mice intra-nasally administered Ag85B-rHPIV2. We found that expression of Ag85B was dispensable for the development of iBALT, suggesting that HPIV2 acted as an iBALT-inducing vector. When iBALT organogenesis was disrupted in Ag85B-rHPIV2-immunized mice, either by neutralization of the lymphotoxin pathway or depletion of CD11b⁺ cells, Ag85B-specific immune responses (i.e. IFN γ-producing T cells and IgA antibody) were diminished in the lung. Furthermore, we found that immunization with Ag85B-rHPIV2 induced neutrophil and eosinophil infiltration temporally after the immunization in the lung. Thus, our results show that iBALT organogenesis contributes to the induction of antigen-specific immune responses by Ag85B-rHPIV2 and that Ag85B-rHPIV2 provokes its immune responses without inducing long-lasting inflammation.

Immune Cell-Epithelial/Mesenchymal Interaction Contributing to Allergic Airway Inflammation Associated Pathology

The primary function of the lung is efficient gas exchange between alveolar air and alveolar capillary blood. At the same time, the lung protects the host from continuous invasion of harmful viruses and bacteria by developing unique epithelial barrier systems. Thus, the lung has a complex architecture comprising a mixture of various types of cells including epithelial cells, mesenchymal cells, and immune cells. Recent studies have revealed that Interleukin (IL-)33, a member of the IL-1 family of cytokines, is a key environmental cytokine that is derived from epithelial cells and induces type 2 inflammation in the barrier organs, including the lung. IL-33 induces allergic diseases, such as asthma, through the activation of various immune cells that express an IL-33 receptor, ST2, including ST2⁺ memory (CD62L^lowCD44^hi) CD4⁺ T cells. ST2⁺ memory CD4⁺ T cells have the capacity to produce high levels of IL-5 and Amphiregulin and are involved in the pathology of asthma. ST2⁺ memory CD4⁺ T cells are maintained by IL-7- and IL-33-produced lymphatic endothelial cells within inducible bronchus-associated lymphoid tissue (iBALT) around the bronchioles during chronic lung inflammation. In this review, we will discuss the impact of these immune cells-epithelial/mesenchymal interaction on shaping the pathology of chronic allergic inflammation. A better understanding of pathogenic roles of the cellular and molecular interaction between immune cells and non-immune cells is crucial for the development of new therapeutic strategies for intractable allergic diseases.

Molecular regulation of peripheral B cells and their progeny in immunity

In this review, Boothby et al. summarize some salient advances toward elucidation of the molecular programming of the fate choices and function of B cells in the periphery. They also note unanswered questions that pertain to differences among subsets of B lymphocytes and plasma cells.

Mature B lymphocytes are crucial components of adaptive immunity, a system essential for the evolutionary fitness of mammals. Adaptive lymphocyte function requires an initially naïve cell to proliferate extensively and its progeny to have the capacity to assume a variety of fates. These include either terminal differentiation (the long-lived plasma cell) or metastable transcriptional reprogramming (germinal center and memory B cells). In this review, we focus principally on the regulation of differentiation and functional diversification of the “B2” subset. An overview is combined with an account of more recent advances, including initial work on mechanisms that eliminate DNA methylation and potential links between intracellular metabolites and chromatin editing.

The Multifaceted B Cell Response to Influenza Virus

Protection from yearly recurring, highly acute infections with a pathogen that rapidly and continuously evades previously induced protective neutralizing Abs, as seen during seasonal influenza virus infections, can be expected to require a B cell response that is too highly variable, able to adapt rapidly, and able to reduce morbidity and death when sterile immunity cannot be garnered quickly enough. As we outline in this Brief Review, the influenza-specific B cell response is exactly that: it is multifaceted, involves both innate-like and conventional B cells, provides early and later immune protection, employs B cells with distinct BCR repertoires and distinct modes of activation, and continuously adapts to the ever-changing virus while enhancing overall protection. A formidable response to a formidable pathogen.

Role of iBALT in Respiratory Immunity

Pulmonary respiration inevitably exposes the mucosal surface of the lung to potentially noxious stimuli, including pathogens, allergens, and particulates, each of which can trigger pulmonary damage and inflammation. As inflammation resolves, B and T lymphocytes often aggregate around large bronchi to form inducible Bronchus-Associated Lymphoid Tissue (iBALT). iBALT formation can be initiated by a diverse array of molecular pathways that converge on the activation and differentiation of chemokine-expressing stromal cells that serve as the scaffolding for iBALT and facilitate the recruitment, retention, and organization of leukocytes. Like conventional lymphoid organs, iBALT recruits naïve lymphocytes from the blood, exposes them to local antigens, in this case from the airways, and supports their activation and differentiation into effector cells. The activity of iBALT is demonstrably beneficial for the clearance of respiratory pathogens; however, it is less clear whether it dampens or exacerbates inflammatory responses to non-infectious agents. Here, we review the evidence regarding the role of iBALT in pulmonary immunity and propose that the final outcome depends on the context of the disease.

Engineering cell heterogeneity into organs-on-a-chip

Organ-on-a-chip development is an application that will benefit from advances in cell heterogeneity characterization because these culture models are intended to mimic in vivo microenvironments, which are complex and dynamic. Due in no small part to advances in microfluidic single cell analysis methods, cell-to-cell variability is an increasingly understood feature of physiological tissues, with cell types from as common as 1 out of every 2 cells to as rare as 1 out of every 100 000 cells having important roles in the biochemical and biological makeup of tissues and organs. Variability between neighboring cells can be transient or maintained, and ordered or stochastic. This review covers three areas of well-studied cell heterogeneity that are informative for organ-on-a-chip development efforts: tumors, the lung, and the intestine. Then we look at how recent single cell analysis strategies have enabled better understanding of heterogeneity within in vitro and in vivo tissues. Finally, we provide a few work-arounds for adapting current on-chip culture methods to better mimic physiological cell heterogeneity including accounting for crucial rare cell types and events.

Inhaled Fine Particles Induce Alveolar Macrophage Death and Interleukin-1α Release to Promote Inducible Bronchus-Associated Lymphoid Tissue Formation

Particulate pollution is thought to function as an adjuvant that can induce allergic responses. However, the exact cell types and immunological factors that initiate the lung-specific immune responses are unclear. We found that upon intratracheal instillation, particulates such as aluminum salts and silica killed alveolar macrophages (AMs), which then released interleukin-1α (IL-1α) and caused inducible bronchus-associated lymphoid tissue (iBALT) formation in the lung. IL-1α release continued for up to 2 weeks after particulate exposure, and type-2 allergic immune responses were induced by the inhalation of antigen during IL-1α release and iBALT formation, even long after particulate instillation. Recombinant IL-1α was sufficient to induce iBALTs, which coincided with subsequent immunoglobulin E responses, and IL-1-receptor-deficient mice failed to induce iBALT formation. Therefore, the AM-IL-1α-iBALT axis might be a therapeutic target for particulate-induced allergic inflammation.

The role of local allergy in the nasal inflammation

Local allergic inflammation (LAI) is recognized recently. 'entopy' was used to define LAI, which was positively correlated with allergen provocation testing, local sIgE up-regulation, inflammatory mediator secretion, and a lack of systemic allergy. The study of LAI is in its infancy and focuses mainly on the respiratory system. It is closely related to nasal inflammation and plays important roles in patients with nonallergic rhinitis (NAR), nonallergic chronic sinusitis with nasal polyps (CRSwNP), and nonallergic fungal rhinosinusitis (NAFRS). Based on studies using nasal allergen provocation testing, 40-57% of patients with NAR exhibited positive results and could be diagnosed as local allergic rhinitis. Total IgE and common airborne allergen-sIgE were up-regulated in eosinophilic CRSwNP patients compared to noneosinophilic CRSwNP patients and healthy controls, possibly due to local allergic inflammation. Some researchers also found that the level of local sIgE was increased in patients with NAFRS; they suggested that local allergic inflammation occurs in NAFRS. Studies of LAI will increase our understanding of nasal inflammation and help to establish novel treatments. However, the diagnosis of local allergic inflammation is complex due to the lack of convenient detection methods. The relationship between local allergic inflammation and systemic allergic inflammation is unclear, and an appropriate treatment for local allergic inflammation is required.

B cell subsets are modulated during allergic airway inflammation but are not required for the development of respiratory tolerance in a murine model

Allergic asthma is a widespread chronic inflammatory disease of the airways. The role of different B cell subsets in developing asthma and respiratory tolerance is not well known. Especially regulatory B (Breg) cells are proposed to be important in asthma regulation. Using wild-type (WT) and B cell-deficient (μMT) mice we investigated how B cells are affected by induction of allergic airway inflammation and respiratory tolerance and whether they are necessary to develop these conditions. WT mice with an asthma-like phenotype, characterized by increased airway hyper reactivity, eosinophilic airway inflammation, mucus hypersecretion and elevated Th2 cytokines, exhibited increased MHCII and CD23 expression on follicular mature B cells in lung, bronchial lymph nodes (bLN) and spleen, which contributed to allergen-specific T cell proliferation in vitro. Germinal center B cell numbers were elevated and associated with increased production of allergen-specific immunoglobulins especially in bLN. In contrast, respiratory tolerance clearly attenuated these B cell alterations and directly enhanced marginal zone precursor B cells, which induced regulatory T cells in vitro. However, μMT mice developed asthma-like and tolerized phenotypes like WT mice. Our data indicate that although B cell subsets are affected by asthma-like and respiratory tolerant phenotypes, B cells are not required for tolerance induction.

The formation and function of tertiary lymphoid follicles in chronic pulmonary inflammation

Tertiary lymphoid follicles (TLFs) can develop in the respiratory tract in response to infections or chronic inflammation. However, their functional relevance remains unclear because they are implicated in both protective and pathological responses. In contrast to homeostatic conditions, external antigens and damage to the lung tissue may drive TLF formation in inflamed lungs, and once established, the presence of pulmonary TLFs may signal the progression of chronic lung disease. This novel concept will be discussed in light of recent work in chronic obstructive pulmonary disease and how changes in the pulmonary microbiota may drive and direct TLF formation and function. We will also discuss the cellularity of TLFs at the pulmonary mucosa, with emphasis on the potential roles of lymphoid tissue inducer cells, and B- and T-cell aggregates, and will examine the function of key chemokines and cytokines including CXCL13 and interleukin-17, in the formation and maintenance of pulmonary TLFs.

Mucosal expression of DEC-205 targeted allergen alleviates an asthmatic phenotype in mice

Considering the rising incidence of allergic asthma, the symptomatic treatments that are currently applied in most cases are less than ideal. Specific immunotherapy is currently the only treatment that is able to change the course of the disease, but suffers from a long treatment duration. A gene based immunization that elicits the targeting of allergens towards dendritic cells in a steady-state environment might have the potential to amend these difficulties. Here we used a replication deficient adenovirus to induce the mucosal expression of OVA coupled to a single-chain antibody against DEC-205. A single intranasal vaccination was sufficient to mitigate an OVA-dependent asthmatic phenotype in a murine model. Invasive airway measurements demonstrated improved lung function after Ad-Dec-OVA treatment, which was in line with a marked reduction of goblet cell hyperplasia and lung eosinophilia. Furthermore OVA-specific IgE titers and production of type 2 cytokines were significantly reduced. Together, the here presented data demonstrate the feasibility of mucosal expression of DEC-targeted allergens as a treatment of allergic asthma.

Inducible Bronchus-Associated Lymphoid Tissue: Taming Inflammation in the Lung

Following pulmonary inflammation, leukocytes that infiltrate the lung often assemble into structures known as inducible Bronchus-Associated Lymphoid Tissue (iBALT). Like conventional lymphoid organs, areas of iBALT have segregated B and T cell areas, specialized stromal cells, high endothelial venules, and lymphatic vessels. After inflammation is resolved, iBALT is maintained for months, independently of inflammation. Once iBALT is formed, it participates in immune responses to pulmonary antigens, including those that are unrelated to the iBALT-initiating antigen, and often alters the clinical course of disease. However, the mechanisms that govern immune responses in iBALT and determine how iBALT impacts local and systemic immunity are poorly understood. Here, we review our current understanding of iBALT formation and discuss how iBALT participates in pulmonary immunity.

Morphometric analysis of inflammation in bronchial biopsies following exposure to inhaled diesel exhaust and allergen challenge in atopic subjects

Background

Allergen exposure and air pollution are two risk factors for asthma development and airway inflammation that have been examined extensively in isolation. The impact of combined allergen and diesel exhaust exposure has received considerably less attention. Diesel exhaust (DE) is a major contributor to ambient particulate matter (PM) air pollution, which can act as an adjuvant to immune responses and augment allergic inflammation. We aimed to clarify whether DE increases allergen-induced inflammation and cellular immune response in the airways of atopic human subjects.

Methods

Twelve atopic subjects were exposed to DE 300 μg.m⁻³ or filtered air for 2 h in a blinded crossover study design with a four-week washout period between arms. One hour following either filtered air or DE exposure, subjects were exposed to allergen or saline (vehicle control) via segmental challenge. Forty-eight hours post-allergen or control exposure, bronchial biopsies were collected. The study design generated 4 different conditions: filtered air + saline (FAS), DE + saline (DES), filtered air + allergen (FAA) and DE + allergen (DEA). Biopsies sections were immunostained for tryptase, eosinophil cationic protein (ECP), neutrophil elastase (NE), CD138, CD4 and interleukin (IL)-4. The percent positivity of positive cells were quantified in the bronchial submucosa.

Results

The percent positivity for tryptase expression and ECP expression remained unchanged in the bronchial submucosa in all conditions. CD4 % positive staining in DEA (0.311 ± 0.060) was elevated relative to FAS (0.087 ± 0.018; p = 0.035). IL-4 % positive staining in DEA (0.548 ± 0.143) was elevated relative to FAS (0.127 ± 0.062; p = 0.034). CD138 % positive staining in DEA (0.120 ± 0.031) was elevated relative to FAS (0.017 ± 0.006; p = 0.015), DES (0.044 ± 0.024; p = 0.040), and FAA (0.044 ± 0.008; p = 0.037). CD138 % positive staining in FAA (0.044 ± 0.008) was elevated relative to FAS (0.017 ± 0.006; p = 0.049). NE percent positive staining in DEA (0.224 ± 0.047) was elevated relative to FAS (0.045 ± 0.014; p = 0.031).

Conclusions

In vivo allergen and DE co-exposure results in elevated CD4, IL-4, CD138 and NE in the respiratory submucosa of atopic subjects, while eosinophils and mast cells are not changed.

Trial registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01792232.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0114-z) contains supplementary material, which is available to authorized users.

Inmunohistochemical detection of mastocytes in tissue from patients with actinic prurigo

BACKGROUND

Actinic prurigo (AP) is a type of photodermatosis, the pathophysiology of which has not been determined. AP has been suggested to be a hypersensitivity reaction to the presence of eosinophils and the local production of IgE.

MATERIAL AND METHODS

Descriptive study, using paraffin blocks of tissue that have been diagnosed with AP from the Dermopathology department, Hospital General Dr. Manuel Gea González. In 66 blocks from 63 patients, eosinophils were identified by hematoxylin and eosin staining, and mastocytes were labeled by immunohistochemistry. Three random microphotographs (40x) were used, and cell counts were calculated as the mean count in the 3 microphotographs.

RESULTS

Forty cases (63.5%) were female, and 23 (36.5%) were male. The mean age was 26.49 ±14.09 years; regarding the evolution time of the disease, the average was 11.93 years ±11.39. In 38 of 63 cases (60%), the lip, skin, and conjunctiva were affected clinically. In 22 of 63 cases (34%), AP cheilitis was the sole manifestation, and in 4 of 63 cases (6%), there were lesions in the skin and conjunctiva. The mean eosinophil count was 9 per case, the average number of mastocytes/field was 28.48 (range 0 to 66) Kruskal-Wallis p=0.001.

CONCLUSIONS

There are elements in AP that mediate the reaction of hypersensitivity type IV b, necessitating the identification of triggering factors.

KEY WORDS

Actinic prurigo, eosinophil, hypersensitivity IV b, IgE, mastocytes.

Immunohistochemical Detection of Markers for Translational Studies of Lung Disease in Pigs and Humans

Genetically engineered pigs are increasingly recognized as valuable models for the study of human disease. Immunohistochemical study of cellular markers of disease is an important tool for the investigation of these novel models so as to evaluate genotype and treatment differences. Even so, there remains a lack of validated markers for pig tissues that can serve as a translational link to human disease in organs such as the lung. Herein, we evaluate markers of cellular inflammation (cluster of differentiation [CD]3, CD79a, B cell lymphoma [BCL] 6, ionized calcium-binding adapter molecule [IBA]1, and myeloperoxidase) and those that may be involved with tissue remodeling (alpha-smooth muscle actin, beta-tubulin-III, lactoferrin, mucin [MUC]5AC, MUC5B, and cystic fibrosis transmembrane conductance regulator [CFTR]) for study of lung tissues. We compare the utility of these markers between pig and human lungs to validate translational relevance of each marker. Our results suggest these markers can be a useful addition in the pathological evaluation of porcine models of human disease.

Poor association of allergen-specific antibody, T- and B-cell responses revealed with recombinant allergens and a CFSE dilution-based assay

BACKGROUND

The adaptive immunity underlying allergy comprises two components, the allergen-specific antibody (i.e. IgE, IgG) and the T-cell response. These two components are responsible for different disease manifestations and can be targeted by different therapeutic approaches. Here, we investigated the association of allergen-specific antibody and T- as well as B-cell responses in pollen-allergic patients using recombinant (r) major birch pollen allergen rBet v 1 and major timothy grass pollen allergen rPhl p 5 as defined antigens.

METHODS

Allergen-specific IgE and IgG antibody responses were determined by ELISA, and allergen-specific T- and B-cell responses were measured in peripheral blood mononuclear cells using a carboxyfluorescein-diacetate-succinimidylester (CFSE) dilution assay.

RESULTS

CFSE staining in combination with T-cell- and B-cell-specific gating allowed discriminating between allergen-specific T-cell and B-cell responses. Interestingly, we identified patients where mainly T cells and others where mainly B cells proliferated in response to allergen stimulation. No association between the level of allergen-specific Ig responses and B- or T-cell proliferation was observed.

CONCLUSION

Purified recombinant allergens in conjunction with CFSE staining allow the dissection of allergen-specific B- and T-cell responses. The dissociation of allergen-specific antibody, and B- and T-cell responses may explain the occurrence of selective IgE- and T-cell-mediated manifestations of allergic inflammation and may be important for the development of diagnostic and therapeutic strategies selectively targeting B cells and T cells.

Bronchial lesions of mouse model of asthma are preceded by immune complex vasculitis and induced bronchial associated lymphoid tissue (iBALT)

We systematically examined by immune histology the lungs of some widely used mouse models of asthma. These models include sensitization by multiple intraperitoneal injections of soluble ovalbumin (OVA) or of OVA with alum, followed by three intranasal or aerosol challenges 3 days apart. Within 24 h after a single challenge there is fibrinoid necrosis of arterial walls with deposition of immunoglobulin (Ig) and OVA and infiltration of eosinophilic polymorphonuclear cells that lasts for about 3 days followed by peribronchial B-cell infiltration and slight reversible goblet cell hypertrophy (GCHT). After two challenges, severe eosinophilic vasculitis is present at 6 h, increases by 72 h, and then declines; B-cell proliferation and significant GCHT and hyperplasia (GCHTH) and bronchial smooth muscle hypertrophy recur more prominently. After three challenges, there is significantly increased induced bronchus-associated lymphoid tissue (iBALT) formation, GCHTH, and smooth muscle hypertrophy. Elevated levels of Th2 cytokines, IL-4, IL-5, and IL-13, are present in bronchial lavage fluids. Sensitized mice have precipitating antibody and positive Arthus skin reactions but also develop significant levels of IgE antibody to OVA but only 1 week after challenge. We conclude that the asthma like lung lesions induced in these models is preceded by immune complex-mediated eosinophilic vasculitis and iBALT formation. There are elevations of Th2 cytokines that most likely produce bronchial lesions that resemble human asthma. However, it is unlikely that mast cell-activated atopic mechanisms are responsible as we found only a few presumed mast cells by toluidine blue and metachromatic staining limited to the most proximal part of the main stem bronchus, and none in the remaining main stem bronchus or in the lung periphery.

Regulatory T cells prevent inducible BALT formation by dampening neutrophilic inflammation

Inducible BALT (iBALT) can amplify pulmonary or systemic inflammatory responses to the benefit or detriment of the host. We took advantage of the age-dependent formation of iBALT to interrogate the underlying mechanisms that give rise to this ectopic, tertiary lymphoid organ. In this study, we show that the reduced propensity for weanling as compared with neonatal mice to form iBALT in response to acute LPS exposure is associated with greater regulatory T cell expansion in the mediastinal lymph nodes. Ab- or transgene-mediated depletion of regulatory T cells in weanling mice upregulated the expression of IL-17A and CXCL9 in the lungs, induced a tissue neutrophilia, and increased the frequency of iBALT to that observed in neonatal mice. Remarkably, neutrophil depletion in neonatal mice decreased the expression of the B cell active cytokines, a proliferation-inducing ligand and IL-21, and attenuated LPS-induced iBALT formation. Taken together, our data implicate a role for neutrophils in lymphoid neogenesis. Neutrophilic inflammation is a common feature of many autoimmune diseases in which iBALT are present and pathogenic, and hence the targeting of neutrophils or their byproducts may serve to ameliorate detrimental lymphoid neogenesis in a variety of disease contexts.

Structure, Organization, and Development of the Mucosal Immune System of the Respiratory Tract

The respiratory tract is served by a variety of lymphoid tissues, including the tonsils, adenoids, nasal-associated lymphoid tissue (NALT), and bronchus-associated lymphoid tissue (BALT), as well as the lymph nodes that drain the upper and lower respiratory tract. Each of these tissues uses unique mechanisms to acquire antigens and respond to pathogens in the local environment and supports immune responses that are tailored to protect those locations. This chapter will review the important features of NALT and BALT and define how these tissues contribute to immunity in the upper and lower respiratory tract, respectively.

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

Rapid and robust recall or 'memory' responses are an essential feature of adaptive immunity. They constitute a defense against reinfection by pathogens, yet arguably do more harm than good in allergic disease. Immunoglobulin (Ig)E antibodies mediate the allergic reaction characterized by immediate hypersensitivity, a manifestation of IgE memory. The origin of IgE memory remains obscure, mainly due to the low proportion of IgE-expressing B cells in the total B cell population. The recent development of ultrasensitive methods for tracking these cells in vivo has overcome this obstacle, and their use has revealed unexpected pathways to IgE memory in the mouse. Here, we review these findings and consider their bearing on our understanding of IgE memory and allergic disease in man.

B cell-intrinsic MyD88 signaling is essential for IgE responses in lungs exposed to pollen allergens

Allergen-specific IgE is linked to asthma pathogenesis, but the underlying mechanisms of IgE production in response to allergen exposure are poorly understood. In this article, we show that B cell-intrinsic MyD88 is essential for IgE/IgG1 production evoked by ragweed pollen instilled into lungs. MyD88-deficient mice showed defective IgE/IgG1 production and germinal center responses to lung instillation of ragweed pollen. However, MyD88 was dispensable for dendritic cell activation and Th2 cell development. B cell-specific deletion of MyD88 replicated the defective Ab production observed in MyD88-deficient mice. Although ragweed pollen contains TLR ligands, TLR2/4/9-deficient mice developed normal allergic responses to ragweed pollen. However, anti-IL-1R1 Ab-treated mice and IL-18-deficient mice showed decreased IgE/IgG1 production with normal Th2 development. Furthermore, B cell-specific MyD88-deficient mice showed reduced IgE/IgG1 production in response to lung instillation of OVA together with IL-1α, IL-1β, or IL-18. Thus, pollen instillation into lungs induces IL-1α/β and IL-18 production, which activates B cell-intrinsic MyD88 signaling to promote germinal center responses and IgE/IgG1 production.

The development and function of mucosal lymphoid tissues: a balancing act with micro-organisms

Mucosal surfaces are constantly exposed to environmental antigens, colonized by commensal organisms and used by pathogens as points of entry. As a result, the immune system has devoted the bulk of its resources to mucosal sites to maintain symbiosis with commensal organisms, prevent pathogen entry, and avoid unnecessary inflammatory responses to innocuous antigens. These functions are facilitated by a variety of mucosal lymphoid organs that develop during embryogenesis in the absence of microbial stimulation as well as ectopic lymphoid tissues that develop in adults following microbial exposure or inflammation. Each of these lymphoid organs samples antigens from different mucosal sites and contributes to immune homeostasis, commensal containment, and immunity to pathogens. Here we discuss the mechanisms, mostly based on mouse studies, that control the development of mucosal lymphoid organs and how the various lymphoid tissues cooperate to maintain the integrity of the mucosal barrier.

B-lymphocyte lineage cells and the respiratory system

Adaptive humoral immune responses in the airways are mediated by B cells and plasma cells that express highly evolved and specific receptors and produce immunoglobulins of most isotypes. In some cases, such as autoimmune diseases or inflammatory diseases caused by excessive exposure to foreign antigens, these same immune cells can cause disease by virtue of overly vigorous responses. This review discusses the generation, differentiation, signaling, activation, and recruitment pathways of B cells and plasma cells, with special emphasis on unique characteristics of subsets of these cells functioning within the respiratory system. The primary sensitization events that generate B cells responsible for effector responses throughout the airways usually occur in the upper airways, tonsils, and adenoid structures that make up the Waldeyer ring. On secondary exposure to antigen in the airways, antigen-processing dendritic cells migrate into secondary lymphoid organs, such as lymph nodes, that drain the upper and lower airways, and further B-cell expansion takes place at those sites. Antigen exposure in the upper or lower airways can also drive expansion of B-lineage cells in the airway mucosal tissue and lead to the formation of inducible lymphoid follicles or aggregates that can mediate local immunity or disease.

The impact of perinatal immune development on mucosal homeostasis and chronic inflammation

The mucosal surfaces of the gut and airways have important barrier functions and regulate the induction of immunological tolerance. The rapidly increasing incidence of chronic inflammatory disorders of these surfaces, such as inflammatory bowel disease and asthma, indicates that the immune functions of these mucosae are becoming disrupted in humans. Recent data indicate that events in prenatal and neonatal life orchestrate mucosal homeostasis. Several environmental factors promote the perinatal programming of the immune system, including colonization of the gut and airways by commensal microorganisms. These complex microbial-host interactions operate in a delicate temporal and spatial manner and have an important role in the induction of homeostatic mechanisms.

A potential new target for asthma therapy: a disintegrin and metalloprotease 10 (ADAM10) involvement in murine experimental asthma

BACKGROUND

Elevated levels of CD23, a natural regulator of IgE production, have been shown to decrease the signs of lung inflammation in mice. The aim of this study was to study the involvement of ADAM10, the primary CD23 sheddase, in experimental asthma.

METHODS

ADAM10 was blocked either by using mice with a B-cell-specific deletion of the protease or pharmacologically by intranasal administration of selective ADAM10 inhibitors. Airway hypersensitivity (AHR) and bronchoaveolar lavage fluid (BALF) eosinophilia and select BALF cytokine/chemokine levels were then determined.

RESULTS

Using an IgE and mast cell-dependent mouse model, B-cell-specific ADAM10(-/-) mice (C57B/6 background) exhibited decreased eosinophilia and AHR when compared with littermate (LM) controls. Treatment of C57B/6 mice with selective inhibitors of ADAM10 resulted in an even further decrease in BALF eosinophilia, as compared with the ADAM10(-/-) animals. Even in the Th2 selective strain, Balb/c, BALF eosinophilia was reduced from 60% to 23% respectively. In contrast, when an IgE/mast cell-independent model of lung inflammation was used, the B-cell ADAM10(-/-) animals and ADAM10 inhibitor treated animals had lung inflammation levels that were similar to the controls.

CONCLUSIONS

These results thus show that ADAM10 is important in the progression of IgE-dependent lung inflammation. The use of the inhibitor further suggested that ADAM10 was important for maintaining Th2 levels in the lung. These results thus suggest that decreasing ADAM10 activity could be beneficial in controlling asthma and possibly other IgE-dependent diseases.

IgE immune complexes stimulate an increase in lung mast cell progenitors in a mouse model of allergic airway inflammation

Mast cell numbers and allergen specific IgE are increased in the lungs of patients with allergic asthma and this can be reproduced in mouse models. The increased number of mast cells is likely due to recruitment of mast cell progenitors that mature in situ. We hypothesized that formation of IgE immune complexes in the lungs of sensitized mice increase the migration of mast cell progenitors to this organ. To study this, a model of allergic airway inflammation where mice were immunized with ovalbumin (OVA) in alum twice followed by three daily intranasal challenges of either OVA coupled to trinitrophenyl (TNP) alone or as immune complexes with IgE-anti-TNP, was used. Mast cell progenitors were quantified by a limiting dilution assay. IgE immune complex challenge of sensitized mice elicited three times more mast cell progenitors per lung than challenge with the same dose of antigen alone. This dose of antigen challenge alone did not increase the levels of mast cell progenitors compared to unchallenged mice. IgE immune complex challenge of sensitized mice also enhanced the frequency of mast cell progenitors per 10(6) mononuclear cells by 2.1-fold. The enhancement of lung mast cell progenitors by IgE immune complex challenge was lost in FcRγ deficient mice but not in CD23 deficient mice. Our data show that IgE immune complex challenge enhances the number of mast cell progenitors in the lung through activation of an Fc receptor associated with the FcRγ chain. This most likely takes place via activation of FcεRI, although activation via FcγRIV or a combination of the two receptors cannot be excluded. IgE immune complex-mediated enhancement of lung MCp numbers is a new reason to target IgE in therapies against allergic asthma.

Opportunities and challenges of the pulmonary route for vaccination

INTRODUCTION

The respiratory tract is an attractive target for the delivery of vaccine antigens. Potential advantages of drug delivery by means of the pulmonary route include accessibility, non-invasiveness, ease of administration, and the possibility to reach an elaborate mucosal network of antigen-presenting cells.

AREAS COVERED

This review discusses current pulmonary vaccination strategies and their advantages and disadvantages.

EXPERT OPINION

To improve efficiency of vaccination and develop new strategies, a well-founded knowledge about composition and characterization of antigen-presenting cell populations throughout the respiratory tract is essential. In particular, respiratory tract dendritic cells, as key antigen-presenting cells in the lung, constitute an ideal target for vaccine delivery. Furthermore, particle size is a key factor when designing new inhalable vaccines, as size determines not only deposition in different respiratory tract compartments, but also how an antigen and its carrier will interact with lung tissue components and immune cells. An increased knowledge of different respiratory tract antigen-presenting cell populations and their interactions with other components of the immune system will enable new targeting strategies to improve the efficacy of pulmonary vaccination.

Bronchus-associated lymphoid tissue (BALT) structure and function

Bronchus-associated lymphoid tissue (BALT) is a constitutive mucosal lymphoid tissue adjacent to major airways in some mammalian species, including rats and rabbits, but not humans or mice. A related tissue, inducible BALT (iBALT), is an ectopic lymphoid tissue that is formed upon inflammation or infection in both mice and humans and can be found throughout the lung. Both BALT and iBALT acquire antigens from the airways and initiate local immune responses and maintain memory cells in the lungs. Here, we discuss the development and function of BALT and iBALT in the context of pulmonary immunity to infectious agents, tumors, and allergens as well as autoimmunity and inflammatory diseases of the lung.

CD23-dependent transcytosis of IgE and immune complex across the polarized human respiratory epithelial cells

IgE-mediated allergic inflammation occurs when allergens cross-link IgE on the surface of immune cells, thereby triggering the release of inflammatory mediators as well as enhancing Ag presentations. IgE is frequently present in airway secretions, and its level can be enhanced in human patients with allergic rhinitis and bronchial asthma. However, it remains completely unknown how IgE appears in the airway secretions. In this study, we show that CD23 (FcεRII) is constitutively expressed in established or primary human airway epithelial cells, and its expression is significantly upregulated when airway epithelial cells were subjected to IL-4 stimulation. In a transcytosis assay, human IgE or IgE-derived immune complex (IC) was transported across a polarized Calu-3 monolayer. Exposure of the Calu-3 monolayer to IL-4 stimulation also enhanced the transcytosis of either human IgE or the IC. A CD23-specific Ab or soluble CD23 significantly reduced the efficiency of IgE or IC transcytosis, suggesting a specific receptor-mediated transport by CD23. Transcytosis of both IgE and the IC was further verified in primary human airway epithelial cell monolayers. Furthermore, the transcytosed Ag-IgE complexes were competent in inducing degranulation of the cultured human mast cells. Because airway epithelial cells are the first cell layer to come into contact with inhaled allergens, our study implies CD23-mediated IgE transcytosis in human airway epithelial cells may play a critical role in initiating and contributing to the perpetuation of airway allergic inflammation.

Regulation of inducible BALT formation and contribution to immunity and pathology

Inducible bronchus-associated lymphoid tissue (iBALT) is an organized tertiary lymphoid structure that is not pre-programmed but develops in response to infection or under chronic inflammatory conditions. Emerging research has shown that iBALT provides a niche for T-cell priming and B-cell education to assist in the clearance of infectious agents, highlighting the prospect that iBALT may be engineered and harnessed to enhance protective immunity against respiratory pathogens. Although iBALT formation is associated with several canonical factors of secondary lymphoid organogenesis such as lymphotoxin-α and the homeostatic chemokines, CXCL13, CCL19, and CCL21, these cytokines are not mandatory for its formation, even though they influence its organization and function. Similarly, lymphoid tissue-inducer cells are not a requisite of iBALT formation. In contrast, dendritic cells are emerging as pivotal players required to form and sustain the presence of iBALT. Regulatory T cells appear to be able to attenuate the development of iBALT, although the underlying mechanisms remain ill-defined. In this review, we discuss facets unique to iBALT induction, the cellular subsets, and molecular cues that govern this process, and the contribution of this ectopic structure toward the generation of immune responses in the pulmonary compartment.

B lymphocytes in inflammatory airway diseases

B lymphocytes are key players in all facets of adaptive immune responses and are responsible for the production of IgE antibodies, initiators of allergic hypersensitivity reactions. Recent evidence indicates that B cells may be a crucial player in allergic and inflammatory airway pathology, directly populating upper and lower airway tissues. This review examines human and animal studies that directly demonstrated the presence of B lymphocytes in airway tissues and elaborates on their function as antibody-secreting cells, antigen-presenting cells and producers of inflammatory and regulatory cytokines. B lymphocytes appear to contribute to multiple facets of immune homeostasis in inflammatory diseases of the upper and lower airways.

Local and systemic IgE in the evaluation and treatment of allergy

Traditional descriptions of type I hypersensitivity and its manifestations center on systemic immunoglobulin E (IgE)-mediated reactions to inciting antigens. Hence, many current diagnostic and therapeutic measures are based on systemic skin testing for allergy, systemic pharmacotherapy, and immunotherapy. Recent developments in rhinology and pulmonology, particularly in defining the phenomenon of local IgE production in various airway inflammatory conditions, have an impact on both medical and surgical diagnosis and management of these conditions. This review includes a discussion of allergy as a systemic disease, current systemic diagnostic and management strategies for allergy, and local IgE presence and synthesis in the upper and lower airways.

Interleukin-12 as an adjuvant for induction of protective antibody responses

Interleukin (IL)-12 is a pivotal cytokine that strongly stimulates Th1-associated cellular immunity. It is now recognized that IL-12 also activates humoral immunity to both T-dependent and T-independent antigens. This has let to considerable interest in exploiting IL-12 as a vaccine adjuvant for protection against various bacterial and viral pathogens, particularly in the lung. Studies examining the efficacy of IL-12-mediated effects on protective antibody response in the mouse model are summarized in this review.

Allergy for a lifetime?

As the key molecule of type-I-hypersensitivity, IgE provides specificity for the allergen and links it to the allergic effector functions. Antibodies are secreted by plasma cells and their precursors, the plasma blasts. The fate of plasma cells is a subject of controversy, with respect to their lifetime and persistence in the absence of allergen. In general, plasma cells were for a long time considered as short-lived end products of B-cell differentiation, and many of them are short-lived, although already for more than 20 years evidence has been provided that IgE-secreting plasma cells can persist over months. Today long-lived, "memory" plasma cells are considered to represent a distinct cellular entity of immunological memory, with considerable therapeutic relevance. Long-lived plasma cells resist current therapeutic and experimental approaches such as immunosuppression, e.g. cyclophosphamide, steroids, X-ray irradiation, anti-CD20 antibodies and anti-inflammatory drugs, while the chronic generation of short-lived plasma cells is sensitive to conventional immunosuppression. The seasonal variation in pollen-specific IgE can be suppressed by immunotherapy, indicating that component of the IgE response, which is stimulated with pollen allergen is susceptible to suppression. Targeting of the remaining long-lived, allergen-specific plasma cells, providing the stable IgE-titers, represents a therapeutic challenge. Here we discuss recent evidence suggesting, why current protocols for the treatment of IgE-mediated allergies fail: Memory plasma cells generated by inhalation of the allergen become long-lived and are maintained preferentially in the bone marrow. They do not proliferate, and are refractory to conventional therapies. Current concepts target plasma cells for depletion, e.g. the proteasome inhibitor bortezomib, BAFF and APRIL antagonists and autologous hematopoietic stem cell transplantation.