IgE receptors

Wildfire Smoke: Health Effects, Mechanisms, and Mitigation

Wildfires are becoming more frequent and intense on a global scale, raising concerns about their acute and long-term effects on human health. We conducted a systematic review of the current epidemiological evidence on wildfire health risks and a meta-analysis to investigate the association between wildfire smoke exposure and various health outcomes. We discovered that wildfire smoke increases the risk of premature deaths and respiratory morbidity in the general population. Meta-analysis of cause-specific mortality and morbidity revealed that wildfire smoke had the strongest associations with cardiovascular mortality (RR: 1.018, 95% CI: 1.014-1.021), asthma hospitalization (RR: 1.054, 95% CI: 1.026-1.082), and asthma emergency department visits (RR: 1.117, 95% CI: 1.035-1.204) in the general population. Subgroup analyses of age found that adults and elderly adults were more susceptible to the cardiopulmonary effects of wildfire smoke. Next, we systematically addressed the toxicological mechanisms of wildfire smoke, including direct toxicity, oxidative stress, inflammatory reactions, immune dysregulation, genotoxicity and mutations, skin allergies, inflammation, and others. We discuss wildfire smoke risk mitigation strategies including public health interventions, regulatory measures, and personal actions. We conclude by highlighting current research limitations and future directions for wildfire research, such as elucidating the complex interactions of wildfire smoke components on human health, developing personalized risk assessment tools, and improving resilience and adaptation strategies to mitigate the health effects of wildfires in changing climate.

Pathophysiology of Congenital High Production of IgE and Its Consequences: A Narrative Review Uncovering a Neglected Setting of Disorders

Elevated serum IgE levels serve as a critical marker for uncovering hidden immunological disorders, particularly inborn errors of immunity (IEIs), which are often misdiagnosed as common allergic conditions. IgE, while typically associated with allergic diseases, plays a significant role in immune defense, especially against parasitic infections. However, extremely high levels of IgE can indicate more severe conditions, such as Hyper-IgE syndromes (HIES) and disorders with similar features, including Omenn syndrome, Wiskott-Aldrich syndrome, and IPEX syndrome. Novel insights into the genetic mutations responsible for these conditions highlight their impact on immune regulation and the resulting clinical features, including recurrent infections, eczema, and elevated IgE. This narrative review uniquely integrates recent advances in the genetic understanding of IEIs and discusses how these findings impact both diagnosis and treatment. Additionally, emerging therapeutic strategies, such as hematopoietic stem cell transplantation (HSCT) and gene therapies, are explored, underscoring the potential for personalized treatment approaches. Emphasizing the need for precise diagnosis and tailored interventions aims to enhance patient outcomes and improve the quality of care for those with elevated IgE levels and associated immunological disorders.

Ameliorative Effect of Imperatorin on Dermatophagoides pteronyssinus-Induced Allergic Asthma by Suppressing the Th2 Response in Mice

Imperatorin is a furanocoumarin derivative and an effective ingredient in several Chinese medicinal herbs. It has favorable expectorant, analgesic, and anti-inflammatory effects. In this study, we investigated whether imperatorin has protective effects against Dermatophagoides pteronyssinus (Der p)-induced asthma in mice. Lung and bronchial tissues were histopathologically examined through hematoxylin–eosin staining. The concentrations of immunoglobin E (IgE), IgG1, IgG2a in serum and those of T helper 1 (Th1) and two cytokines and eosinophil-activated chemokines in bronchoalveolar lavage fluid (BALF) were detected using an enzyme immunoassay. Histological examination revealed that imperatorin reduced inflammatory cell infiltration, mucus hypersecretion, and endothelial cell hyperplasia. The examination also indicated that imperatorin could reduce the inflammatory cell count in BALF as well as IgE and IgG1 expression in serum, but IgG2a expression was significantly increased. Imperatorin reduced the production of interleukin (IL)-4, IL-5, and IL-13 by Th2, promoted the production of interferon-γ and IL-12 by Th1, and increased the production of IL-10 in bronchoalveolar lavage fluid. These findings suggest that imperatorin has a considerable anti-inflammatory effect on Der p-induced allergic asthma in mice.

Anti-Apoptotic and Anti-Inflammatory Effects of an Ethanolic Extract of Lycium chinense Root against Particulate Matter 10-Induced Cell Death and Inflammation in RBL-2H3 Basophil Cells and BALB/c Mice

Particulate matters (PMs) from polluted air cause diverse pulmonary and cardiovascular diseases, including lung inflammation. While the fruits (Goji) of Lycium trees are commonly consumed as traditional medicine and functional food ingredients, the majority of their roots are discarded as by-products. To enhance the industrial applicability of Lycium roots, we prepared an ethanol extract (named GR30) of L. chinense Miller roots and evaluated its potential protective effects against particulate matter 10 (PM10)-induced inflammation and immune cell death. The GR30 treatment (0–500 μg/mL) significantly attenuated the PM10-induced cell cycle arrest, DNA fragmentation and mitochondria-dependent apoptosis in RBL-2H3 basophil cells. GR30 also significantly antagonized the PM10-induced expression of proinflammatory cytokines (IL-4, IL-13, and TNF-α) and COX2 expression through downregulation of MAPKs (ERK and JNK) signalling pathway. Oral administration of GR30 (200–400 mg/kg) to PM10 (20 mg/mL)-challenged mice significantly reduced the serum levels of IgE and the expression of TNF-α and Bax in lung tissues, which were elevated by PM10 exposure. These results revealed that the ethanolic extract (GR30) of L. chinense Miller roots exhibited anti-inflammatory and cyto-protective activity against PM10-induced inflammation and basophil cell death, and thus, it would be useful in functional food industries to ameliorate PM-mediated damage to respiratory and immune systems.

Pharmacological approaches to target type 2 cytokines in asthma

Asthma is the most common chronic lung disease, affecting more than 250 million people worldwide. The heterogeneity of asthma phenotypes represents a challenge for adequate assessment and treatment of the disease. However, approximately 50% of asthma patients present with chronic type 2 inflammation initiated by alarmins, such as IL-33 and thymic stromal lymphopoietin (TSLP), and driven by the T_H2 interleukins IL-4, IL-5 and IL-13. These cytokines have therefore become important therapeutic targets in asthma. Here, we discuss current knowledge on the structure and functions of these cytokines in asthma. We review preclinical and clinical data obtained with monoclonal antibodies (mAbs) targeting these cytokines or their receptors, as well as novel strategies under development, including bispecific mAbs, designed ankyrin repeat proteins (DARPins), small molecule inhibitors and vaccines targeting type 2 cytokines.

The role of allergen-specific IgE, IgG and IgA in allergic disease

Immunoglobulin E (IgE)‐mediated allergy is the most common hypersensitivity disease affecting more than 30% of the population. Exposure to even minute quantities of allergens can lead to the production of IgE antibodies in atopic individuals. This is termed allergic sensitization, which occurs mainly in early childhood. Allergen‐specific IgE then binds to the high (FcεRI) and low‐affinity receptors (FcεRII, also called CD23) for IgE on effector cells and antigen‐presenting cells. Subsequent and repeated allergen exposure increases allergen‐specific IgE levels and, by receptor cross‐linking, triggers immediate release of inflammatory mediators from mast cells and basophils whereas IgE‐facilitated allergen presentation perpetuates T cell–mediated allergic inflammation. Due to engagement of receptors which are highly selective for IgE, even tiny amounts of allergens can induce massive inflammation. Naturally occurring allergen‐specific IgG and IgA antibodies usually recognize different epitopes on allergens compared with IgE and do not efficiently interfere with allergen‐induced inflammation. However, IgG and IgA antibodies to these important IgE epitopes can be induced by allergen‐specific immunotherapy or by passive immunization. These will lead to competition with IgE for binding with the allergen and prevent allergic responses. Similarly, anti‐IgE treatment does the same by preventing IgE from binding to its receptor on mast cells and basophils. Here, we review the complex interplay of allergen‐specific IgE, IgG and IgA and the corresponding cell receptors in allergic diseases and its relevance for diagnosis, treatment and prevention of allergy.

Autologous enzyme-linked immunosorbent facilitated antigen binding detects IgE-blocking activity based on direct competition between allergen-specific IgE and non-IgE

Aim: To measure IgE-blocking activity induced by allergen immunotherapy (AIT) by an enzyme-linked immunosorbent facilitated antigen binding (ELIFAB) assay based on autologous immunoglobulin competition. Methods: The developed ELIFAB assay was used to investigate the kinetics of IgE-blocking activity in 87 patients at multiple AIT treatment time points, in comparison to the changes in IgG4. Results: High ELIFAB response was observed until 2.5 months of AIT, then significantly decreased after 4 months and remained suppressed during the 3-year AIT period. After treatment cessation, the ELIFAB response was maintained at the level seen at the 4-6 month treatment time point, similar to IgG4, indicating sustained IgE-blocking activity related to IgG4. Conclusion: This ELIFAB assay measures the IgE-blocking activity for autologous allergen-specific IgE and non-IgE during and after immunotherapy. It is suited for measuring the sustained IgE-blocking activity induced by AIT.

IgE in the pathophysiology and therapy of food allergy

Food allergy is becoming a major public health issue, with no regulatory approved therapy to date. Food allergy symptoms range from skin rash and gastrointestinal symptoms to anaphylaxis, a potentially fatal systemic allergic shock reaction. IgE antibodies are thought to contribute importantly to key features of food allergy and anaphylaxis, and measurement of allergen-specific IgE is fundamental in diagnosing food allergy. This review will discuss recent advances in the regulation of IgE production and IgE repertoires in food allergy. We will describe the current understanding of the role of IgE and its high-affinity receptor FcεRI in food allergy and anaphylaxis, by reviewing insights gained from analyses of mouse models. Finally, we will review data derived from clinical studies of the effect of anti-IgE therapeutic monoclonal antibodies (mAbs) in food allergy, and recent insight on the efficiency and mechanisms through which these mAbs block IgE effector functions.

Directing a rational design of aptamer-based fluorescence anisotropy assay for sensitive detection of immunoglobulin E by site-specific binding study

Mapping aptamer-protein interactions is important for characterization and applications of aptamers against proteins. We describe here probing affinity interactions between aptamer and immunoglobulin E (IgE) with a fluorescence anisotropy (FA) approach using a series of aptamer probes having single fluorescein (FAM) label at individual nucleotide (A, C, T). Studies of binding between IgE and aptamer probes revealed several possible close-contact sites, e.g., T9, T10, T11, T13, C15, and T17 of a 37-nt aptamer with a stem-loop secondary structure. FAM labeling on these sites resulted in much higher FA values (higher than 0.230 for T10, T11, T13 and C15) of aptamer-IgE complexes than the distant sites (e.g., terminals) of aptamer probably because the bound IgE close to these sites significantly restricted local rotation of FAM. Close-contact site labeled aptamer probes with high affinity allowed to develop a more sensitive FA assay for IgE than distant site labeled aptamers. The FA assay using T10-labeled aptamer with a dissociation constant (K_d) about 0.8 nM enabled selective detection of IgE at 20 pM and large FA increase upon IgE addition. We also found A12, C14, A25, and T27 were important for IgE-aptamer binding as FAM labeling at these sites significantly reduced aptamer affinity. FA study showed the loop region of this stem-loop aptamer was crucial for affinity binding, and IgE bound to the loop. This FA method will be helpful for understanding aptamer-protein binding and making a rational design of aptamer affinity assays for proteins.

Environmental exposure to endotoxin and its health outcomes: A systematic review

Exposure to endotoxin occurs environmentally and occupationally. There are several differences between them in terms of the variety and severity of health outcomes, possible exposed groups and type and route of exposure. Occupational exposures caused adverse health outcomes in almost all cases, but there is disparity in the incidence of significant health outcomes due to environmental exposure to endotoxin. This study has therefore endeavoured to investigate health outcomes from environmental exposure to endotoxin. A systematic review was conducted of three databases and non-occupational studies reporting the environmental concentration of endotoxin, and observed health outcomes in exposed groups were included in the review (n = 27). The studies showed that first exposure to endotoxin occurs in infancy by the inhalation route. Inhalation is the only exposure route that can induce inflammation as the main symptom of exposure to endotoxin. The studies included were conducted using four approaches: molecular immunology, measurement of lung volumes, clinical sensitisation test and diagnosis of asthmatic and respiratory symptoms such as wheezing. By the immunological approach, all the included studies reported that environmental exposure to endotoxin, especially at a younger age, has a protective effect on the incidence of asthma in adolescence. The main disparity observed was in studies using the approach of diagnosed asthma. Overall, however, they confirm the protective effect of exposure to endotoxin although, in the case of children with non-atopic asthma, the results could be different.

A genome-wide cross-trait analysis from UK Biobank highlights the shared genetic architecture of asthma and allergic diseases

Clinical and epidemiological data suggest that asthma and allergic diseases are associated and may share a common genetic etiology. We analyzed genome-wide single-nucleotide polymorphism (SNP) data for asthma and allergic diseases in 33,593 cases and 76,768 controls of European ancestry from the UK Biobank. Two publicly available independent genome wide association studies (GWAS) were used for replication. We have found a strong genome-wide genetic correlation between asthma and allergic diseases (r_g = 0.75, P = 6.84×10⁻⁶²). Cross trait analysis identified 38 genome-wide significant loci, including 7 novel shared loci. Computational analysis showed that shared genetic loci are enriched in immune/inflammatory systems and tissues with epithelium cells. Our work identifies common genetic architectures shared between asthma and allergy and will help to advance our understanding of the molecular mechanisms underlying co-morbid asthma and allergic diseases.

The Natural Course of Atopic Dermatitis and the Association with Asthma

In this paper, we aimed to explore the potential mechanism underlying atopic dermatitis (AD) and its association with asthma. The BALB/c mice were randomly assigned to three groups, including the vehicle control (VD) group, the AD group, and the treatment (TR) group. The AD mice model was successfully constructed in the AD and TR group. The dermatitis severity scores and skin lesions were significantly increased in AD mice after DNCB application. Airway responsiveness in the AD group was significantly higher than in the TR group. The number of inflammatory cells was increased in skin lesions and bronchoalveolar lavage fluid (BALF) of AD mice. The levels of IL-4, IL-5, IFN-γ, and OVA-IgE in BALF supernatants of mice in the AD group were higher than those in the VC group. All the changes in AD mice were decreased by tacrolimus. These results indicate that AD may be a significant risk factor for atopic asthma development.

Recent advances in food allergy

Summary Food allergy is a public health issue that has significantly increased worldwide in the past decade, affecting consumers’ quality of life and making increasing demands on health service resources. Despite recent advances in many areas of diagnosis and treatment, our general knowledge of the basic mechanisms of the disease remain limited i.e., not at pace with the exponential number of new cases and the explosion of new technologies. Many important key questions remain: What defines a major allergen? Why do some individuals develop food allergies and others do not? Which are the environmental factors? Could the environmental factors be monitored through epigenetics or modified by changes in the microbiome? Can tolerance to food be induced? Why are some foods more likely to trigger allergies than others? Does the route and timing of exposure have any role on sensitization? These and many other related questions remain unanswered. In this short review some of these topics are addressed in the light of recent advances in the area.

Specific allergen immunotherapy attenuates allergic airway inflammation in a rat model of Alstonia scholaris pollen induced airway allergy

Pollen grains are well established to be an important cause of respiratory allergy. Current pharmacologic therapies for allergic asthma do not cure the disease. Allergen specific immunotherapy is the only treatment method which re-directs the immune system away from allergic response leading to a long lasting effect. The mechanism by which immunotherapy achieves this goal is an area of active research world-wide. The present experimental study was designed to develop an experimental model of allergic lung inflammation based on a relevant human allergen, Alstonia scholaris pollen, and to establish the immunological and cellular features of specific allergen immunotherapy using this same pollen extract. Our results revealed that Alstonia scholaris pollen sensitization and challenge causes eosinophilic airway inflammation with mucin hypersecretion. This is associated with increased total IgE, increased expression of FcɛRI on lung mast cells and increased levels of IL-4, IL-5 & IL-13 as confirmed by ELISA, in-situ immunofluorescence and FACS assay. Allergen specific immunotherapy reduced airway inflammation and also decreased total IgE level, FcɛRI expression, IL-4, IL-5 & IL-13 levels. It was further noted that the reduction of these levels was more by intra-nasal route than by intra-peritoneal route. Thus we present a novel animal model of Alstonia scholaris pollen allergic disease and specific allergen immunotherapy which will pave the way towards the development of better treatment modalities.

Interferon at the crossroads of allergy and viral infections

IFN-α/β was first described as a potent inhibitor of viral replication, but it is now appreciated that IFN signaling plays a pleiotropic role in regulating peripheral T cell functions. Recently, IFN-α/β was shown to block human Th2 development by suppressing the transcription factor GATA3. This effect is consistent with the role for IFN-α/β in suppressing allergic inflammatory processes by blocking granulocyte activation and IL-4-mediated B cell isotype switching to IgE. With the consideration of recent studies demonstrating a defect in IFN-α/β secretion in DCs and epithelial cells from individuals with severe atopic diseases, there is an apparent reciprocal negative regulatory loop in atopic individuals, whereby the lack of IFN-α/β secretion by innate cells contributes to the development of allergic Th2 cells. Is it possible to overcome these events by treating with IFN-α/β or by inducing its secretion in vivo? In support of this approach, case studies have documented the therapeutic potential of IFN-α/β in treating steroid-resistant allergic asthma and other atopic diseases. Additionally, individuals with asthma who are infected with HCV and respond to IFN therapy showed a reduction in symptoms and severity of asthma attacks. These findings support a model, whereby allergic and antiviral responses are able to cross-regulate each other, as IgER cross-linking of pDCs prevents IFN-α/β production in response to viral infection. The clinical importance of upper-respiratory viruses in the context of allergic asthma supports the need to understand how these pathways intersect and to identify potential therapeutic targets.

Histamine production by human neutrophils

Histamine is an important mediator in the development of allergic reactions. Only a small subset of human cell types is able to produce histamine. No previous studies have shown that human neutrophils are among them. The present work was undertaken to analyze whether human neutrophils produce histamine, and to determine what agonists are involved in histamine production by human neutrophils. The expression of histidine decarboxylase in human neutrophils was established by quantitative PCR, Western blotting, and flow cytometry analysis. The activity of the enzyme was determined by ELISA, which measured histamine in the culture supernatant of neutrophils stimulated with a set of classical agonists. Human neutrophils are bona fide histamine-producing cells. Neutrophils store ∼0.29 pg/cell and release ∼50% of the histamine content in an antigen-dependent manner and on stimulation with other neutrophil agonists. Basal expression of histidine decarboxylase, the rate-limiting enzyme in histamine production, is higher in neutrophils from patients with allergies than from healthy donors. Our results cannot be ascribed to cell contamination for several reasons. LPS failed to induce histamine release by basophils, whereas it induced histamine release by neutrophils; and we did not detect basophils, monocytes, or lymphocytes in our neutrophil preparations. Eosinophils, albeit detected, were only 0.001-0.004% of the final cell population, and they did not store or release histamine on antigen or LPS stimulation. Antigens to which patients with allergies were sensitized stimulated release of histamine from neutrophils. These observations represent a novel view of neutrophils as possible source of histamine in the allergic diseases.

Inflammatory and degranulation effect of yellow sand on RBL-2H3 cells in relation to chemical and biological constituents

Recent studie pointed out that allergic diseases have increased during the Asian dust storm event (ADSE) in Japan. Daily observations and the atmospheric concentrations of yellow sand (YS) aerosol have been increasing. In this study, YS samples collected from three sites of Japan during ADSE in 2009-2010 were used. The particles were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence-energy dispersive spectrometer (XRF-EDS). We investigate ability of YS extract on enhancing the chemical mediator release and cytokine production from rat basophilic leukemia (RBL-2H3) cells. The dust particles at Fukuoka and Tsukuba were abundant in aluminum (Al), iron (Fe), potassium (K) and titan (Ti) than those at Naha. Concentration of the trace endotoxin and Cryptomeria japonica pollen allergen (Cry j 1) were measured in YS extract. After exposure of RBL-2H3 cells to YS extract, the β-hexosaminidase (β-hex) release, tumor necrosis factor-alpha (TNF-α) production were enhanced in RBL-2H3 cells. This process depends on endotoxin, Cry j 1 and other allergen present in the YS extract. YS water extract also show a strong cytotoxic effect on the cells. This data suggest that low levels of endotoxin and Cry j 1 in YS may cause allergy during the ADSE.

Intravenous immunoglobulin in the management of lupus nephritis

The occurrence of nephritis in patients with systemic lupus erythematosus is associated with increased morbidity and mortality. The pathogenesis of lupus nephritis is complex, involving innate and adaptive cellular and humoral immune responses. Autoantibodies in particular have been shown to be critical in the initiation and progression of renal injury, via interactions with both Fc-receptors and complement. One approach in the management of patients with lupus nephritis has been the use of intravenous immunoglobulin. This therapy has shown benefit in the setting of many forms of autoantibody-mediated injury; however, the mechanisms of efficacy are not fully understood. In this paper, the data supporting the use of immunoglobulin therapy in lupus nephritis will be evaluated. In addition, the potential mechanisms of action will be discussed with respect to the known involvement of complement and Fc-receptors in the kidney parenchyma. Results are provocative and warrant additional clinical trials.

Inhibitory effect of tannins from galls of Carpinus tschonoskii on the degranulation of RBL-2H3 Cells

In this study, the anti-allergy potency of thirteen tannins isolated from the galls on buds of Carpinus tschonoskii (including two tannin derivatives) was investigated. RBL-2H3 (rat basophilic leukemia) cells were incubated with these compounds, and the release of β-hexosaminidase and cytotoxicity were measured. Of the thirteen tannins, tetragalloylglucose (2), pentagalloylglucose (3), casuarictin (4), and casuarinin (9) were the most potent inhibitors, and all the tannins showed no cytotoxic effect after 24 h of incubation. The results obtained suggest that tannins from C. tschonoskii are capable of inhibiting allergic reactions and may be useful for the treatment or prevention of type I allergic diseases.

The high affinity IgE receptor (FcεRI) expression and function in airway smooth muscle

The airway smooth muscle (ASM) is no longer considered as merely a contractile apparatus and passive recipient of growth factors, neurotransmitters and inflammatory mediators signal but a critical player in the perpetuation and modulation of airway inflammation and remodeling. In recent years, a molecular link between ASM and IgE has been established through Fc epsilon receptors (FcεRs) in modulating the phenotype and function of these cells. Particularly, the expression of high affinity IgE receptor (FcεRI) has been noted in primary human ASM cells in vitro and in vivo within bronchial biopsies of allergic asthmatic subjects. The activation of FcεRI on ASM cells suggests a critical yet almost completely ignored network which may modulate ASM cell function in allergic asthma. This review is intended to provide a historical perspective of IgE effects on ASM and highlights the recent updates in the expression and function of FcεRI, and to present future perspectives of activation of this pathway in ASM cells.

The increasing challenge of discovering asthma drugs

The prevalence of asthma continues to rise. Current drugs provide symptomatic relief to some, but not all, patients. Despite the need for new therapeutics, and a huge research effort, only four novel agents from two classes of drugs - the antileukotrienes and an anti-IgE antibody - have been approved in the last 30 years. This review highlights three particular issues that contribute to the challenge of identifying new therapeutics. First is an over-reliance on animal models of allergy to define targets and expectations of efficacy that has met with poor translation to the clinical setting. While sensitivity to particular aeroallergens is one key risk factor for asthma, atopy and asthma are not synonymous, and while about half of adult asthmatics are atopic the incidence of allergic asthma is probably <50%. The second issue is a fundamental disconnect between the directions of basic research and clinical research. Basic research has developed a detailed, reductive, unifying mechanism of antigen-induced, T helper type 2 cell-mediated airway inflammation as the root cause of asthma. In contrast, clinical research has started to identify multiple asthma phenotypes with differing cellular components, mediators and sensitivities to asthma drugs, and probably varying underlying factors including susceptibility genes. Finally, different features of asthma - bronchoconstriction, symptoms, and exacerbations - respond diversely to treatment; effects that are not captured in animal models which do not develop asthma per se, but utilize unvalidated surrogate markers. Basic research needs to better integrate and utilize the clinical research findings to improve its relevance to drug discovery efforts.

New insights into the mechanism and management of allergic diseases: atopic dermatitis

Rapidly increasing knowledge on the complex background of atopic dermatitis (AD) on the genetic, immunological and environmental level in combination with the continuous improvement in our diagnostic options has initiated an ongoing discussion on factors, which primarily promote the disease on one hand and mechanisms which emerge rather secondarily as a consequence of disease-specific modifications, on the other hand. Beside a sustained search for reliable and meaningful diagnostic tools for elicitors of the disease, novel therapeutic approaches are required, as most of the treatments of AD are limited to symptomatic therapies. In contrast, therapeutic approaches selectively regulating aberrant pathophysiological mechanisms in AD itself would be much more effective and promising.

Interferons modulate Fc epsilon RI-dependent production of autoregulatory IL-10 by circulating human monocytoid dendritic cells

BACKGROUND

Immature human blood monocytoid dendritic cells (mDCs) express high-affinity receptors for IgE (Fc epsilon RI), yet their exact function and regulation remain poorly understood.

OBJECTIVE

We sought to characterize Fc epsilon RI-dependent cytokine responses and their regulation in circulating human blood mDCs.

METHODS

Fc epsilon RI-dependent cytokine responses of circulating mDCs were studied by using anti-Fc epsilon RI alpha stimulation. Plasmacytoid dendritic cell (pDC) cross-regulation through Toll-like receptor 9 on these responses was investigated by examining the effects of exogenous IFN-alpha pretreatment and by coculturing pDCs and mDCs stimulated with CpG. Culture supernatants were analyzed by means of ELISA to determine cytokine levels. Cell markers were determined by means of flow cytometry.

RESULTS

mDCs express marked levels of Fc epsilon RI (net mean fluorescence intensity, 196 +/- 49; n = 4). After Fc epsilon RI-dependent activation in mDCs, TNF-alpha (2189 +/- 864 pg/10(6) mDCs, n = 3) levels were upregulated within 4 hours, whereas IL-10 (112 +/- 47 pg/10(6) mDCs, n = 3) levels were detectable only after 24 hours of incubation. After adding IL-10-neutralizing antibody, TNF-alpha Fc epsilon RI-dependent responses were significantly augmented (3903 +/- 197 pg/10(6) mDCs, P < .01, n = 3). Conversely, recombinant IL-10 dose-dependently inhibited Fc epsilon RI-mediated TNF-alpha responses up to 86% +/- 3% (n = 3, P < .001). Pretreatment of mDCs with IFN-alpha (100 U/mL) enhanced Fc epsilon RI-dependent secretion of IL-10 by 3.2-fold (183 +/- 11 pg/10(6) mDCs, n = 4) compared with that seen in untreated cells (57 +/- 33 pg/10(6) mDCs, P < .001, n = 4). In pDC/mDC cocultures pretreated with CpG, Fc epsilon RI-dependent IL-10 secretion by mDCs was similarly augmented by 3-fold.

CONCLUSIONS

Autocrine secretion of IL-10, a critical autoregulator of Fc epsilon RI-dependent proinflammatory responses in mDCs, is cross-regulated by IFN-alpha, a major product of Toll-like receptor 9 responses in pDCs that normally promotes T(H)1 immunity.

Cellular aspects of atopic dermatitis

Atopic dermatitis (AD) is a highly pruritic, chronic, and relapsing inflammatory skin disease. Recent interest in AD has been sparked by reports of its increasing prevalence and its contribution to increasing health care costs. A precise understanding of immunologic mechanisms is crucial for the development of effective treatment strategies for AD. Various studies reveal that AD has a multifactorial cause with the activation of complex immunologic and inflammatory pathways. This review will discuss cellular-mediated immunological pathomechanisms of AD. Emphasis will be given to the role played by T cells, antigen-presenting cells, eosinophils, and keratinocytes. We also examine the immunological effect of superantigens on various inflammatory cells including T regulatory cells.

Decoding IgE Fc receptors

Immunoglobulin E (IgE) plays a central role in the pathogenesis of allergic diseases by interacting with two membrane receptors: high-affinity FcepsilonRI and low-affinity FcepsilonRII (CD23). Allergeninduced IgE-occupied FcepsilonRI aggregation on the mast cell or basophil cell surface leads to the activation of intracellular signaling events and eventually the release of pre-formed and de novo synthesized inflammatory mediators. The role of FcepsilonRII in allergic diseases has been proposed to include regulation of IgE synthesis, enhanced histamine release from basophils, and a contribution to Ag-IgE complex presentation but the exact function of CD23 remains poorly understood. This review summarizes some new developments in IgE Fc-receptor studies with an emphasis on regulation of FcepsilonRI expression and signal transduction, including monomeric IgE, lipid raft segregation, and some recently identified negative regulators. A better understanding of signaling events following IgE FcR aggregation will shed new light on how allergy patients might be treated more safely and effectively.

Inductions of histidine decarboxylase in mouse tissues following systemic antigen challenge: contributions made by mast cells, non-mast cells and IL-1

BACKGROUND

Previous findings suggest that antigen challenge (AC) may induce histidine decarboxylase (HDC) in cells other than mast cells (MCs) via MC-derived IL-1. We examined this hypothesis.

METHODS

Mice were sensitized to ovalbumin. After the sensitization, an AC was delivered intravenously.

RESULTS

In control mice, AC markedly induced HDC at a postanaphylactic time in the liver, lung, spleen, and ears. In MC-deficient W/W(v) mice, AC also induced HDC, although the effect was weaker than in control mice. AC increased IL-1 in the tissues, the pattern being similar in W/W(v) and control mice. AC induced HDC similarly in IL-1-deficient and control mice. In control mice, AC decreased histamine in the tissues (except the liver) for several hours.

CONCLUSION

(1) AC induces HDC in both MC-dependent and MC-independent ways. (2) AC induces IL-1 mostly in non-MCs, but this IL-1 is not a prerequisite for the induction of HDC by AC. (3) HDC induction may contribute to the replenishment of the reduced pool of MC histamine in the anaphylactic period. (4) In the case of MC-dependent HDC induction, AC may stimulate MCs in such a way as to induce HDC within the MCs themselves, and/or AC-stimulated MCs may stimulate HDC induction in other cells, which will need to be directly identified in future studies.

Targeting dendritic cells in allergen immunotherapy

Allergen immunotherapy is a well-established strategy for treating allergic diseases with the goal of inducing allergen-specific tolerance. Identified mechanisms contributing to the therapeutic effect of immunotherapy include a shift of T helper 2 (Th2)-type immune responses to a modified Th2 immune response, a change of the balance of IgE-producing B cells to the production of IgG subtypes, in addition to increased IL-10 and TGF-beta secretion and activation of the suppressive functions of regulatory T-cells. Dendritic cells (DCs), which as outposts of the immune system are capable of T-cell priming through efficient allergen uptake by IgE receptors expressed on their cell surface. Most of the hypotheses concerning the function of DCs as facilitators of allergen-specific tolerance in allergen immunotherapy remain speculative. Therefore, studies must focus on the functional changes of DCs under immunotherapy to close the gap of knowledge about their exact role. These experimental data should help confirm the hypothesis of DCs as efficient silencers and potential target cells and take advantage of the bivalent character and tolerogenic properties of DCs.

Diagnosis and treatment of atopic dermatitis in children and adults: European Academy of Allergology and Clinical Immunology/American Academy of Allergy, Asthma and Immunology/PRACTALL Consensus Report

There are remarkable differences in the diagnostic and therapeutic management of atopic dermatitis practiced by dermatologists and pediatricians in different countries. Therefore, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams who were given the task of finding a consensus to serve as a guideline for clinical practice in Europe as well as in North America. The consensus report is part of the PRACTALL initiative, which is endorsed by both academies.

IgE-mediated allergen presentation and blocking antibodies: regulation of T-cell activation in allergy

It is well established that both the production of IgE by B lymphocytes and the maturation and recruitment of eosinophils in late-phase reactions are dependent on the activation of allergen-specific type-2 T-helper cells. What is less well known is the fact that efficient activation of allergen-specific T cells upon low-dose exposure to allergens is critically dependent on IgE-mediated or -facilitated allergen presentation. In fact, changes in the level of IgE-mediated allergen presentation may account for many of the immunological effects described for specific immunotherapy or anti-IgE treatment. This review aims to summarize the current knowledge, and will discuss the clinical relevance of blocking IgG antibodies induced by specific immunotherapy and anti-IgE monoclonal antibodies that both interfere with IgE-mediated allergen presentation.

Histamine and prostaglandin E up-regulate the production of Th2-attracting chemokines (CCL17 and CCL22) and down-regulate IFN-gamma-induced CXCL10 production by immature human dendritic cells

Effector memory T helper 2 (Th2) cells that accumulate in target organs (i.e. skin or bronchial mucosa) have a central role in the pathogenesis of allergic disorders. To date, the factors that selectively trigger local production of Th2-attracting chemokines remain poorly understood. In mucosa, at the sites of allergen entry, immature dendritic cells (DC) are in close contact with mast cells. Histamine and prostaglandin E2 (PGE2) are two mediators released by allergen-activated mast cells that favour the polarization of maturing DC into Th2-polarizing cells. We analysed here the effects of histamine and PGE2 on the prototypic, Th2-(CCL17, CCL22) versus Th1-(CXCL10) chemokine production by human DC. We report that histamine and PGE2 dose-dependently up-regulate CCL17 and CCL22 by monocyte-derived immature DC. These effects were potentiated by tumour necrosis factor-alpha, still observed in the presence of the Th1-cytokine interferon-gamma (IFN-gamma) and abolished by the immunomodulatory cytokine interleukin-10. In addition, histamine and PGE2 down-regulated IFN-gamma-induced CXCL10 production by monocyte-derived DC. These properties of histamine and PGE2 were observed at the transcriptional level and were mediated mainly through H2 receptors for histamine and through EP2 and EP4 receptors for PGE2. Finally, histamine and PGE2 also up-regulated CCL17 and CCL22 and decreased IFN-gamma-induced CXCL10 production by purified human myeloid DC. In conclusion, these data show that, in addition to polarizing DC into mature cells that promote naïve T-cell differentiation into Th2 cells, histamine and PGE2 may act on immature DC to trigger local Th2 cell recruitment through a selective control of Th1/Th2-attracting chemokine production, thereby contributing to maintain a microenvironment favourable to persistent immunoglobulin E synthesis.

Are basophil histamine release and high affinity IgE receptor expression involved in asymptomatic skin sensitization?

BACKGROUND

Immunoglobulin (Ig)E-sensitized persons with positive skin prick test, but no allergy symptoms, are classified as being asymptomatic skin sensitized (AS). The allergic type 1 disease is dependant on IgE binding to the high affinity IgE-receptor (FcepsilonRI) expressed on basophils and mast cells. However, a relationship between the AS status and FcepsilonRI has not been investigated. We aimed to characterize basophils from AS by looking at histamine release (HR) (sensitivity and reactivity) and the FcepsilonRI molecule, and compare it with nonatopic (NA) or allergic (A) persons.

METHODS

Blood was obtained from NA (n = 14), grass and/or birch A persons (n = 17) and mono-sensitized grass or birch pollen AS (n = 12). The basophil sensitivity and reactivity were examined by anti-IgE triggered HR. Surface expression of FcepsilonRI and IgE were measured by flow cytometry, FcepsilonRIalpha protein was identified using a radioimmunoassay and Western blot. mRNA coding for the classic FcepsilonRIbeta-chain and the truncated form (FcepsilonRIbetaT) were determined by real-time PCR.

RESULTS

The AS group was less reactive than NA or A persons when triggered by anti-IgE and had a significant higher number of nonresponders. However, there was no difference in sensitivity among the three groups and furthermore; the groups did not vary in FcepsilonRI- and IgE-surface expression, FcepsilonRIalpha-protein level or beta/betaT ratio.

CONCLUSION

Basophils from AS persons are less reactive and include more nonresponders than basophils from NA and A persons, but do not differ regarding the FcepsilonRI molecule.

Fc receptors as determinants of allergic reactions

Activation of the high-affinity receptor for IgE (FcepsilonRI) on allergic effector cells induces a multitude of positive signals via immunoreceptor tyrosine-based activation motifs, which leads to the rapid manifestation of allergic inflammatory reactions. As a counterbalance, the coaggregation of the IgG receptor FcgammaRIIB mediates inhibitory signals via immunoreceptor tyrosine-based inhibition motifs. Advances in the positive and negative regulation of Fc receptor expression and signaling have shed light on the role of Fc receptors in our immune system, indicating them to be bifunctional, inhibitory and activating structures. Based on these findings, exciting new therapeutic strategies have been developed, such as the use of chimeric fusion proteins, which concomitantly activate FcepsilonRI and FcgammaRIIB. These new approaches successfully take advantage of the bivalent character of Fc receptors and pave the way for innovative strategies to modulate allergic immune reactions.

Comparative analysis of nasal and oral mucosa dendritic cells

BACKGROUND

Mucosal dendritic cells (DC) play a crucial role in tolerance induction as seen in mucosal immunotherapy of atopic diseases. Nevertheless little is known about the phenotypical differences of oral and nasal mucosal DC (nmDC). Recently, we could show that oral mucosal myeloid CD1a(+) DC (omDC) differ from their skin counterparts especially by the expression of high affinity receptor for immunoglobulin E (IgE; FcepsilonRI). However, expression pattern of FcepsilonRI and phenotypical characteristics of CD1a(+) nmDC have not been elucidated in detailed yet.

METHODS

We performed detailed phenotypical comparison of nmDC and omDC of atopic and nonatopic individuals.

RESULTS

As reported for omDC, FcepsilonRI on nmDC of atopic donors was elevated and mostly occupied by IgE while FcepsilonRI was present only in low amounts on nmDC of nonatopic donors. Nevertheless, the highest FcepsilonRI expression has been observed on omDC. Furthermore, significant amounts of costimulatory molecules CD40, CD80 and CD86 could be detected on nmDC that expressed more CD80 compared with omDC. Moreover, nmDC displayed less major histocompatability complex (MHC) class I and II molecules than omDC. In addition, nmDC expressed more C-type lectins CD205, CD206 as well as myeloid marker CD11b while omDC displayed increased expression of CD207 and lipopolysaccharide (LPS) receptor CD14.

CONCLUSION

Together these data imply that nmDC phenotypical differ from omDC which might result in diverse functional properties and might be of relevance for selecting routes for immunotherapy of atopic diseases. Moreover these data provide a basis for further studies investigating immunological mechanisms underlying mucosal immunotherapy.

The role of immunoglobulin E and immune inflammation: implications in allergic rhinitis

Immunoglobulin E (IgE) plays a critical role in the allergic inflammatory process in diseases such as allergic rhinitis. Cross-linking IgE bound to its receptor on cells by multivalent allergens initiates a chain of events resulting in allergic immune responses. Mast cells and basophils are involved in the early, immediate response, which is marked by cellular degranulation and the release of proinflammatory mediators, including histamine. Antigen-presenting cells are also activated by allergen-loaded IgE, resulting in immunomodulation of T-cell responses. The IgE molecule binds to two types of receptors, the high-affinity (Fc epsilonRI) and low-affinity (Fc epsilonRII or CD23) receptors, that have differing properties important in mediating allergen-induced responses. New therapies targeting the IgE molecule reduce allergen-stimulated immune responses and improve the clinical symptoms in subjects with allergic rhinitis. Understanding the role of the IgE molecule is necessary to appreciate the development and use of novel therapies targeting its actions.

The immunoglobulin E receptor: expression and regulation

The interaction of immunoglobulin E (IgE) and its receptors is critical for the manifestation of allergic disease. Currently, IgE receptors include the high-affinity Fc epsilonRI and the low-affinity Fc epsilonRII. Fc epsilonRI is a tetrameric or trimeric complex, and each has distinct expression patterns and unique functional consequences. In general, serum levels of IgE regulate Fc epsilonRI expression, and novel therapies that lower the concentration of IgE have provided insights into the contribution of this receptor in allergic disease. Newer therapies targeting Fc epsilonRI-signaling elements and the low-affinity IgE receptor, Fc epsilonRII (CD23), are being developed.

Seafood allergy: lessons from clinical symptoms, immunological mechanisms and molecular biology

Food allergy consists of a wide range of disorders that result from adverse immune responses to dietary antigens. Manifestations of allergic response includes acute, potentially fatal anaphylactic reactions and a variety of chronic diseases that mainly affect the gastrointestinal tract, skin, and respiratory tract. Tools for clinical diagnosis and management, which have not changed much in the past two decades, include the clinical history, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. On the other hand, recent immunological and molecular biological research have enhanced our understanding of the mechanisms of these disorders and revealed the identities of many food allergens. Here, we will discuss seafood allergies with respect to the clinical manifestations, diagnosis, immunological mechanisms, and molecular biology of seafood allergens. Furthermore, potential applications and future directions in the clinical management of seafood allergies are discussed.

Induction of cyclooxygenase-2 expression by allergens in lymphocytes from allergic patients

Cyclooxygenase (COX) is a key enzyme in prostaglandin (PG) synthesis. Up-regulation of COX-2 expression is responsible for increased PG release during inflammatory conditions and is thought to be also involved in allergic states. In this study, we demonstrate that in human T, B and natural killer lymphocytes from allergic patients, COX-2 expression became induced upon cell challenge with specific allergens and that this process is presumably IgE dependent and occurs after CD23 receptor ligation. This induction took place at both mRNA and protein levels and was accompanied by PGD2 release. IgE-dependent lymphocyte treatment elicited, in parallel, an activation of the MAPK p38 and extracellular signal-regulated kinase 1/2, an enhancement of calcineurin (CaN) activity, and an increase of the DNA-binding activity of the nuclear factor of activated T cells and of NF-kappaB, with a concomitant decrease in the levels of the cytosolic inhibitor of kappaB, IkappaB. In addition, specific chemical inhibitors of MAPK, such as PD098059 and SB203580, as well as MG-132, an inhibitor of proteasomal activity, abolished allergen-induced COX-2 up-regulation, suggesting that this process is mediated by MAPK and NF-kappaB. However, induction of COX-2 expression was not hampered by the CaN inhibitor cyclosporin A. We also examined the effect of a selective COX-2 inhibitor, NS-398, on cytokine production by human lymphocytes. Treatment with NS-398 severely diminished the IgE-dependently induced production of IL-8 and TNF-alpha. These results underscore the relevant role of lymphocyte COX-2 in allergy and suggest that COX-2 inhibitors may contribute to the improvement of allergic inflammation through the reduction of inflammatory mediator production by human lymphocytes.

Atopic march: link to upper airways

PURPOSE OF REVIEW

This review examines the role of the upper airways in the atopic march. Evidence examining the theory that allergic rhinitis precedes asthma will be discussed. In addition, the role of allergic rhinitis as an end point in the atopic march will be reviewed.

RECENT FINDINGS

Ciprandi and colleagues found that nasal symptoms, airflow and markers of inflammation (eosinophils, cytokine levels) directly correlated with lower airway markers. This confirms previous studies finding that many patients with allergic rhinitis have lower airway hyperreactivity or bronchial hyperresponsiveness and the link between upper and lower airways. Leynaert and colleagues questioned over 90 000 individuals and found that patients with rhinitis have increased risk for asthma and lower airway reactivity compared with patients without rhinitis. In the German Multicenter Atopy Study, a longitudinal study of 1300 children, patients with atopic dermatitis were found to have increased risk for asthma at 7 years of age. Patients with atopic dermatitis and no wheezing in the first 3 years, however, did not have an increased risk for developing current wheezing or bronchial hyperresponsiveness at 7 years of age. It was proposed that atopic dermatitis and asthma are linked, but atopic dermatitis does not precede asthma.

SUMMARY

Allergic rhinitis is a risk factor for asthma and can precede asthma in the atopic march.

Research upregulation of CD23 (FcepsilonRII) expression in human airway smooth muscle cells (huASMC) in response to IL-4, GM-CSF, and IL-4/GM-CSF

BACKGROUND

Airway smooth muscle cells play a key role in remodeling that contributes to airway hyperreactivity. Airway smooth muscle remodeling includes hypertrophy and hyperplasia. It has been previously shown that the expression of CD23 on ASMC in rabbits can be induced by the IgE component of the atopic serum. We examined if other components of atopic serum are capable of inducing CD23 expression independent of IgE.

METHODS

Serum starved huASMC were stimulated with either IL-4, GM-CSF, IL-13, IL-5, PGD2, LTD4, tryptase or a combination of IL-4, IL-5, IL-13 each with GM-CSF for a period of 24 h. CD23 expression was analyzed by flow cytometry, western blot, and indirect immunofluorescence.

RESULTS

The CD23 protein expression was upregulated in huASMC in response to IL-4, GM-CSF, and IL-4/GM-CSF. The percentage of cells with increased fluorescence intensity above the control was 25.1 +/- 4.2% (IL-4), 15.6 +/- 2.7% (GM-CSF) and 32.9 +/- 13.9% (IL-4/GMCSF combination)(n = 3). The protein content of IL-4/GMCSF stimulated cells was significantly elevated. Expression of CD23 in response to IL-4, GM-CSF, IL-4/GM-CSF was accompanied by changes in cell morphology including depolymerization of isoactin fibers, cell spreading, and membrane ruffling. Western blot revealed abundant expression of the IL-4Ralpha and a low level expression of IL-2Rgammac in huASMC. Stimulation with IL-4 resulted in the phosphorylation of STAT-6 and an increase in the expression of the IL-2Rgammac.

CONCLUSION

CD23 on huASMC is upregulated by IL-4, GM-CSF, and IL-4/GM-CSF. The expression of CD23 is accompanied by an increase in cell volume and an increase in protein content per cell, suggesting hypertrophy. Upregulation of CD23 by IL-4/GM-CSF results in phenotypic changes in huASMC that could play a role in cell migration or a change in the synthetic function of the cells. Upregulation of CD23 in huASMC by IL-4 and GM-CSF can contribute to changes in huASMC and may provide an avenue for new therapeutic options in asthma targeting ASMC.

Membrane IgE Binds and Activates FcεRI in an Antigen-Independent Manner

Interaction of secretory IgE with FcepsilonRI is the prerequisite for allergen-driven cellular responses, fundamental events in immediate and chronic allergic manifestations. Previous studies reported the binding of soluble FcepsilonRIalpha to membrane IgE exposed on B cells. In this study, the functional interaction between human membrane IgE and human FcepsilonRI is presented. Four different IgE versions were expressed in mouse B cell lines, namely: a truncation at the Cepsilon2-Cepsilon3 junction of membrane IgE isoform long, membrane IgE isoform long (without Igalpha/Igbeta BCR accessory proteins), and both epsilonBCRs (containing membrane IgE isoforms short and long). All membrane IgE versions activated a rat basophilic leukemia cell line transfected with human FcepsilonRI, as detected by measuring the release of both preformed and newly synthesized mediators. The interaction led also to Ca(2+) responses in the basophil cell line, while membrane IgE-FcepsilonRI complexes were detected by immunoprecipitation. FcepsilonRI activation by membrane IgE occurs in an Ag-independent manner. Noteworthily, human peripheral blood basophils and monocytes also were activated upon contact with cells bearing membrane IgE. In humans, the presence of FcepsilonRI in several cellular entities suggests a possible membrane IgE-FcepsilonRI-driven cell-cell dialogue, with likely implications for IgE homeostasis in physiology and pathology.

Characterization of FcepsilonRI-bearing CD123 blood dendritic cell antigen-2 plasmacytoid dendritic cells in atopic dermatitis

BACKGROUND

The high-affinity receptor for IgE (FcepsilonRI) on myeloid dendritic cells has been shown to play a major role in atopic dermatitis (AD). Plasmacytoid dendritic cells (pDCs), which are instrumental in the defense of viral infections, are present in reduced amounts in the skin of patients with AD, which is characterized by a high susceptibility to viral infections.

OBJECTIVE

We explored phenotypical and functional characteristics of pDC in the peripheral blood of patients with AD and healthy individuals.

METHODS

Blood dendritic cell antigen-2+CD123+ pDCs were enriched from the peripheral blood of patients with AD and studied in functional assays.

RESULTS

Skin-homing molecules such as cutaneous lymphocyte antigen and L-selectin CD62L were expressed in lower levels on pDCs of patients with AD. pDCs expressed high amounts of IgE-occupied FcepsilonRI. Further, FcepsilonRI aggregation on pDCs impaired the surface expression of MHC I and II, induced the production of IL-10, and enhanced the apoptosis of pDCs. Importantly, FcepsilonRI preactivated pDC produced less IFN-alpha and IFN-beta after stimulation with CpG motifs and enhanced the outcome of immune responses of the TH2 type.

CONCLUSION

From these data, we conclude that FcepsilonRI-bearing pDCs from patients with AD (1) are different from pDCs of healthy individuals, (2) might be important in the pathophysiology of AD, and (3) contribute to the enhanced susceptibility of patients with AD to viral infections.

Human neutrophils synthesize IL-8 in an IgE-mediated activation

It has been demonstrated that neutrophils are responsible for the release of large amounts of the inflammatory chemokine interleukin-8 (IL-8), associated with inflammation. To further define the mechanisms implicated, we have analyzed the response of human neutrophils from allergic patients to specific antigens or challenge with anti-immunoglobulin (Ig)E antibodies. Neutrophils showed a dose- and time-dependent production of IL-8. The release of the cytokine was parallel to expression of IL-8 mRNA analyzed by the polymerase chain reaction. This expression was transient-it occurred after 3 h of anti-IgE treatment and was maintained for 18 h. Trifluoperazine, EGTA, reduced nicotinamide adenine dinucleotide phosphate-oxidase inhibitors, and reactive oxygen species (ROS) scavengers inhibited IL-8 production, indicating a critical dependence of calcium and oxidative stress. Moreover, an inhibitory effect of cyclosporin A, an immunosuppressor that inhibits calcineurin activity, on IL-8 release and IL-8 mRNA expression was observed. This is the first evidence of the involvement of ROS and calcium/calcineurin in IgE-dependent IL-8 production. These findings open new perspectives into the functional role of neutrophils in IgE-associated diseases.

Tyrosine kinase inhibitors: a new approach for asthma

The pathogenesis of allergic asthma involves the interplay of inflammatory cells and airway-resident cells, and of their secreted mediators including cytokines, chemokines, growth factors and inflammatory mediators. Receptor tyrosine kinases are important for the pathogenesis of airway remodeling. Activation of epidermal growth factor (EGF) receptor kinase and platelet-derived growth factor (PDGF) receptor kinase leads to hyperplasia of airway smooth muscle cells, epithelial cells and goblet cells. Stimulation of non-receptor tyrosine kinases (e.g. Lyn, Lck, Syk, ZAP-70, Fyn, Btk, Itk) is the earliest detectable signaling response upon antigen-induced immunoreceptor activation in inflammatory cells. Cytokine receptor dimerization upon ligand stimulation induces activation of Janus tyrosine kinases (JAKs), leading to recruitment and phosphorylation of signal transducer and activator of transcription (STAT) for selective gene expression regulation. Activation of chemokine receptors can trigger JAK-STAT pathway, Lck, Fyn, Lyn, Fgr, and Syk/Zap-70 to induce chemotaxis of inflammatory cells. Inhibitors of tyrosine kinases have been shown in vitro to block growth factor-induced hyperplasia of airway-resident cells; antigen-induced inflammatory cell activation and cytokine synthesis; cytokine-mediated pro-inflammatory gene expression in inflammatory and airway cells; and chemokine-induced chemotaxis of inflammatory cells. Recently, anti-inflammatory effects of tyrosine kinase inhibitors (e.g. genistein, tyrphostin AG213, piceatannol, tyrphostin AG490, WHI-P97, WHI-P131, Syk antisense) in animal models of allergic asthma have been reported. Therefore, development of inhibitors of tyrosine kinases can be a very attractive strategy for the treatment of asthma.

Cross-talk between Fc receptors and integrins

Fc receptors (FcRs) and integrins are both key players of immune responses. These receptors are capable of independent signaling that leads to various cell functions. Recently, it is becoming clear that these receptors are also capable of modulating each other's responses. This modulation is achieved by direct physical interactions of the receptors on the cell surface, or by one receptor modifying the signaling pathway of the other receptor. Receptor co-localization and resonance energy transfer studies have shown that Fc receptors and integrins interact on the cell surface. Biochemical and functional studies have shown that signaling from Fc receptors modulates integrin adhesiveness through a process called "inside-out signaling". Other studies also show that the signaling from integrins modulates Fc receptor responses such as adhesion to immune complexes and cell mediated antibody-dependent cytotoxicity. This bi-directional cross-talk between Fc receptors and integrins is very important for the final cell function. Here, we review the latest information about interactions between Fc receptors and integrins.

Characterization of dendritic cells from human oral mucosa: a new Langerhans' cell type with high constitutive FcepsilonRI expression

BACKGROUND

The oral mucosa represents a unique immunologic unit with a high frequency of native allergen contact within the gastrointestinal tract in which immune tolerance is the natural outcome of allergen contact. Although Langerhans' cells (LC), known to play a crucial role in initiating allergen-dependent immune responses in the skin, have also been detected in the oral mucosa, little is known about their phenotype and exact physiologic role.

OBJECTIVE

To elucidate whether LC from oral mucosa (oLC) differ from skin LC (sLC), these cells were subjected to detailed comparative analysis.

METHODS

Crude epidermal and oral mucosa cell suspensions were prepared by trypsinization. oLC and sLC were compared phenotypically by flow cytometry techniques and functionally in T-cell proliferation assays.

RESULTS

In contrast to sLC, freshly isolated oLC expressed significantly higher amounts of MHC class I and II, as well as costimulatory molecules CD40, CD80/B7.1, and CD86/B7.2. oLC displayed FcgammaRIII/CD16 and FcgammaRI/CD64. Most surprisingly, oLC constitutively expressed the high affinity receptor for IgE (FcepsilonRI) even in nonatopic donors. FcepsilonRI expression on oLC was further increased and correlated with the serum IgE levels in atopic individuals. oLC showed a higher allogeneic stimulatory activity than sLC, whereas the activation of autologous T cells correlated to the FcepsilonRI expression.

CONCLUSION

Taken together, our results strongly indicate that oLC profoundly differ from their skin counterparts. The constitutive high expression of FcepsilonRI on oLC could point to particular skills of these cells within the regional immune system of the oral mucosa.