Systemic activation of basophils and eosinophils: markers and consequences

Nomenclature of allergic diseases and hypersensitivity reactions: Adapted to modern needs: An EAACI position paper

The exponential growth of precision diagnostic tools, including omic technologies, molecular diagnostics, sophisticated genetic and epigenetic editing, imaging and nano-technologies and patient access to extensive health care, has resulted in vast amounts of unbiased data enabling in-depth disease characterization. New disease endotypes have been identified for various allergic diseases and triggered the gradual transition from a disease description focused on symptoms to identifying biomarkers and intricate pathogenetic and metabolic pathways. Consequently, the current disease taxonomy has to be revised for better categorization. This European Academy of Allergy and Clinical Immunology Position Paper responds to this challenge and provides a modern nomenclature for allergic diseases, which respects the earlier classifications back to the early 20th century. Hypersensitivity reactions originally described by Gell and Coombs have been extended into nine different types comprising antibody- (I-III), cell-mediated (IVa-c), tissue-driven mechanisms (V-VI) and direct response to chemicals (VII). Types I-III are linked to classical and newly described clinical conditions. Type IVa-c are specified and detailed according to the current understanding of T1, T2 and T3 responses. Types V-VI involve epithelial barrier defects and metabolic-induced immune dysregulation, while direct cellular and inflammatory responses to chemicals are covered in type VII. It is notable that several combinations of mixed types may appear in the clinical setting. The clinical relevance of the current approach for allergy practice will be conferred in another article that will follow this year, aiming at showing the relevance in clinical practice where various endotypes can overlap and evolve over the lifetime.

High Transcriptional Activity and Clinical Correlations in Eosinophils of Patients with Late-Onset Asthma

Background

The immunological features of eosinophils in early-onset asthma (EOA) differ from those in late-onset asthma (LOA). Clinical trials of anti-interleukin-5 (IL-5) treatment for severe eosinophilic asthma showed a better response for LOA patients than EOA patients. We wonder if the transcriptional activity of activated eosinophils was different in EOA and LOA.

Methods

Eosinophils obtained from well-controlled EOA and LOA patients and normal subjects were compared in terms of the mRNA expression of activation-related genes and specific markers related to cell functions in eosinophils activated by IL-5 or IL-17. The correlation between mRNA expression and clinical features and lung function was further analyzed.

Results

The transcriptional expression of most genes was higher in activated eosinophils from LOA patients than in those from EOA patients and normal subjects. After IL-17 stimulation, the expression of certain genes was higher in atopic EOA patients than in non-atopic EOA patients. Similar observation was noted in obese EOA patients. After IL-5 stimulation, the transcriptional expression of most genes in eosinophils from LOA patients was negatively correlated with indicators of lung function. These correlations were less pronounced in EOA patients: After IL-17 stimulation, some genes in EOA patients were negatively correlated with post-bronchodilator changes in lung function.

Conclusion

This study describes differences in the transcriptional active patterns of eosinophils and their correlation to atopy and obesity by age of onset. High transcriptional activity in activated eosinophils and a negative correlation to lung function indicate the importance of eosinophils in the pathogenesis of LOA.

The combination of Ara h 2-sIgE and basophil activation test could be an alternative to oral food challenge in cases of suspected peanut allergy

BACKGROUND

Most children with peanut sensitisation do not have a clinical peanut allergy (PA). Oral food challenge (OFC) is then necessary to diagnose PA and assess the reactive dose of the allergen. However, OFC is laborious to perform, expensive and stressful. We evaluated whether in vitro tests, such as basophil activation test (BAT), allergen-specific IgE (sIgE) and their combination, could be used to replace OFC for the diagnosis of PA in children.

METHODS

Ninety-one patients aged 6 months to 18 years with suspected PA were prospectively recruited. These patients then underwent an OFC to assess PA. Whole peanut-sIgE, Ara h 2-sIgE, Ara h 8-sIgE and %CD63+ basophils (CCR3+ /SCClow ) to peanut measured by BAT were investigated for PA diagnosis.

RESULTS

Forty-one patients had a positive peanut OFC, and the remaining 50 were only sensitised. All patients with Ara h 2-sIgE >7 kUA /L were allergic to peanut. A threshold of 6% for activated basophils yielded a sensitivity of 95% and a specificity of 54%. All patients with Ara h 2-sIgE ≤7 kUA /L and BAT ≤6% (n = 22) had a negative OFC except for one who presented an oral syndrome due to PR-10 sensitisation.

CONCLUSIONS

We have shown that Ara h 2-sIgE >7 kUA/L is a discriminating threshold for the diagnosis of PA. Furthermore, when Ara h 2-sIgE ≤7 kUA/L and BAT ≤6%, patients do not need to adjust their diet and, thus, do not need an OFC.

Towards an FDA-cleared basophil activation test

Food allergy is a global health problem affecting up to 10% of the world population. Accurate diagnosis of food allergies, however, is still a major challenge in medical offices and for patients seeking alternative avenues of diagnosis. A flawless test to confirm or rule out a food allergy does not exist. The lack of optimum testing methods to establish precise clinical correlations remains a major obstacle to effective treatment. Certain IgE measurement methods, including component testing, have received FDA clearance, but they have been used primarily as an analytical tool and not to establish clinical correlations. Most allergy tests are still carried out within the laboratory, and skin tests outside a laboratory setting that are used for food allergy diagnosis rely on non-standardized allergens, according to the FDA definition. Epitope mapping and basophil activation test (BAT) have recently been proposed as a means of establishing better clinical correlations. Yet neither have received FDA clearance for widespread distribution. Of the two methods, the BAT has the advantage of being a functional assay. Over the past few years, several large private practice groups in the United States, have developed BAT as a clinical assay and have started using it in patient care. Given this clinical experience, the vast number of papers published on BAT (more than 1,400 as of 2022) and the trend toward increasing FDA regulation, it is essential to understand the roadmap for regulatory clearance of this assay.

Integrative transcriptomic analysis in human and mouse model of anaphylaxis identifies gene signatures associated with cell movement, migration and neuroinflammatory signalling

Background

Anaphylaxis is an acute life-threatening allergic reaction and a concern at a global level; therefore, further progress in understanding the underlying mechanisms and more effective strategies for diagnosis, prevention and management are needed.

Objective

We sought to identify the global architecture of blood transcriptomic features of anaphylaxis by integrating expression data from human patients and mouse model of anaphylaxis.

Methods

Bulk RNA-sequencings of peripheral whole blood were performed in: i) 14 emergency department (ED) patients with acute anaphylaxis, predominantly to Hymenoptera venom, ii) 11 patients with peanut allergy undergoing double-blind, placebo-controlled food challenge (DBPCFC) to peanut, iii) murine model of IgE-mediated anaphylaxis. Integrative characterisation of differential gene expression, immune cell-type-specific gene expression profiles, and functional and pathway analysis was undertaken.

Results

1023 genes were commonly and significantly dysregulated during anaphylaxis in ED and DBPCFC patients; of those genes, 29 were also dysregulated in the mouse model. Cell-type-specific gene expression profiles showed a rapid downregulation of blood basophil and upregulation of neutrophil signature in ED and DBPCFC patients and the mouse model, but no consistent and/or significant differences were found for other blood cells. Functional and pathway analysis demonstrated that human and mouse blood transcriptomic signatures of anaphylaxis follow trajectories of upregulation of cell movement, migration and neuroinflammatory signalling, and downregulation of lipid activating nuclear receptors signalling.

Conclusion

Our study highlights the matched and extensive blood transcriptomic changes and suggests the involvement of discrete cellular components and upregulation of migration and neuroinflammatory pathways during anaphylaxis.

Hypersensitivity and in-stent restenosis in coronary stent materials

Coronary heart disease (CHD) is a type of cardiovascular disease with the highest mortality rate worldwide. Percutaneous transluminal coronary intervention (PCI) is the most effective method for treating CHD. However, in-stent restenosis (ISR), a long-term complication after PCI, affects the prognosis of patients with CHD. Previous studies have suggested that hypersensitivity reactions induced by metallic components may be one of the reasons of this complication. With the emergence of first- and second-generation drug-eluting stents (DES), the efficacy and prognosis of patients with CHD have greatly improved, and the incidence of ISR has gradually decreased to less than 10%. Nevertheless, DES components have been reported to induce hypersensitivity reactions, either individually or synergistically, and cause local inflammation and neointima formation, leading to long-term adverse cardiovascular events. In this article, we described the relationship between ISR and hypersensitivity from different perspectives, including its possible pathogenesis, and discussed their potential influencing factors and clinical significance.

Current and Emerging Strategies to Inhibit Type 2 Inflammation in Atopic Dermatitis

Type 2 immunity evolved to combat helminth infections by orchestrating a combined protective response of innate and adaptive immune cells and promotion of parasitic worm destruction or expulsion, wound repair, and barrier function. Aberrant type 2 immune responses are associated with allergic conditions characterized by chronic tissue inflammation, including atopic dermatitis (AD) and asthma. Signature cytokines of type 2 immunity include interleukin (IL)-4, IL-5, IL-9, IL-13, and IL-31, mainly secreted from immune cells, as well as IL-25, IL-33, and thymic stromal lymphopoietin, mainly secreted from tissue cells, particularly epithelial cells. IL-4 and IL-13 are key players mediating the prototypical type 2 response; IL-4 initiates and promotes differentiation and proliferation of naïve T-helper (Th) cells toward a Th2 cell phenotype, whereas IL-13 has a pleiotropic effect on type 2 inflammation, including, together with IL-4, decreased barrier function. Both cytokines are implicated in B-cell isotype class switching to generate immunoglobulin E, tissue fibrosis, and pruritus. IL-5, a key regulator of eosinophils, is responsible for eosinophil growth, differentiation, survival, and mobilization. In AD, IL-4, IL-13, and IL-31 are associated with sensory nerve sensitization and itch, leading to scratching that further exacerbates inflammation and barrier dysfunction. Various strategies have emerged to suppress type 2 inflammation, including biologics targeting cytokines or their receptors, and Janus kinase inhibitors that block intracellular cytokine signaling pathways. Here we review type 2 inflammation, its role in inflammatory diseases, and current and future therapies targeting type 2 pathways, with a focus on AD.

Role of Eosinophils in Intestinal Inflammation and Fibrosis in Inflammatory Bowel Disease: An Overlooked Villain?

Eosinophils are leukocytes which reside in the gastrointestinal tract under homeostatic conditions, except for the esophagus which is normally devoid of eosinophils. Research on eosinophils has primarily focused on anti-helminth responses and type 2 immune disorders. In contrast, the search for a role of eosinophils in chronic intestinal inflammation and fibrosis has been limited. With a shift in research focus from adaptive to innate immunity and the fact that the eosinophilic granules are filled with inflammatory mediators, eosinophils are becoming a point of interest in inflammatory bowel diseases. In the current review we summarize eosinophil characteristics and recruitment as well as the current knowledge on presence, inflammatory and pro-fibrotic functions of eosinophils in inflammatory bowel disease and other chronic inflammatory conditions, and we identify research gaps which should be covered in the future.

MR1-dependent immune surveillance of the skin contributes to pathogenesis and is a photobiological target of UV light therapy in a mouse model of atopic dermatitis

BACKGROUND

Mucosal-associated invariant T (MAIT) cells are unconventional T cells which recognize microbial metabolites presented by the major histocompatibility complex class I-related molecule MR1. Although MAIT cells have been shown to reside in human and murine skin, their contribution to atopic dermatitis (AD), an inflammatory skin disease associated with barrier dysfunction and microbial translocation, has not yet been determined.

METHODS

Genetic deletion of MR1 and topical treatment with inhibitory MR1 ligands, which result in the absence and functional inhibition of MAIT cells, respectively, were used to investigate the role of MR1-dependent immune surveillance in a MC903-driven murine model of AD.

RESULTS

The absence or inhibition of MR1 arrested AD disease progression through the blockade of both eosinophil activation and recruitment of IL-4- and IL-13-producing cells. In addition, the therapeutic efficacy of phototherapy against MC903-driven AD could be increased with prior application of folate, which photodegrades into the inhibitory MR1 ligand 6-formylpterin.

CONCLUSION

We identified MAIT cells as sentinels and mediators of cutaneous type 2 immunity. Their pathogenic activity can be inhibited by topical application or endogenous generation, via phototherapy, of inhibitory MR1 ligands.

Eosinophils and eosinophil-associated disorders: immunological, clinical, and molecular complexity

Eosinophils and their mediators play a crucial role in various reactive states such as bacterial and viral infections, chronic inflammatory disorders, and certain hematologic malignancies. Depending on the underlying pathology, molecular defect(s), and the cytokine- and mediator-cascades involved, peripheral blood and tissue hypereosinophilia (HE) may develop and may lead to organ dysfunction or even organ damage which usually leads to the diagnosis of a HE syndrome (HES). In some of these patients, the etiology and impact of HE remain unclear. These patients are diagnosed with idiopathic HE. In other patients, HES is diagnosed but the etiology remains unknown — these patients are classified as idiopathic HES. For patients with HES, early therapeutic application of agents reducing eosinophil counts is usually effective in avoiding irreversible organ damage. Therefore, it is important to systematically explore various diagnostic markers and to correctly identify the disease elicitors and etiology. Depending on the presence and type of underlying disease, HES are classified into primary (clonal) HES, reactive HES, and idiopathic HES. In most of these patients, effective therapies can be administered. The current article provides an overview of the pathogenesis of eosinophil-associated disorders, with special emphasis on the molecular, immunological, and clinical complexity of HE and HES. In addition, diagnostic criteria and the classification of eosinophil disorders are reviewed in light of new developments in the field.

Elevated Levels of Activated and Pathogenic Eosinophils Characterize Moderate-Severe House Dust Mite Allergic Rhinitis

Eosinophils play a critical role in the pathogenesis of allergic airway inflammation. However, the relative importance of eosinophil activation and pathogenicity in driving the progression of disease severity of allergic rhinitis (AR) remains to be defined. We aimed to assess the relation of activated and pathogenic eosinophils with disease severity of patients with AR. Peripheral blood and nasal samples were collected from patients with mild (n = 10) and moderate-severe (n = 21) house dust mite AR and healthy control subjects (n = 10) recruited prospectively. Expressions of activation and pathogenic markers on eosinophils in the blood and nose were analyzed by flow cytometry. The eosinophilic cation protein- (ECP-) releasing potential and the pro-Th2 function of blood eosinophils were compared between the mild and moderate-severe patients and healthy controls. Our results showed that the numbers of activated (CD44⁺ and CD69⁺) and pathogenic (CD101⁺CD274⁺) eosinophils in the blood and nose as well as blood eosinophil progenitors were increased in moderate-severe AR compared with the mild patients and healthy controls. In addition, the levels of activated and pathogenic eosinophils in the blood were positively correlated with the total nasal symptom score and serum ECP and eosinophil peroxidase (EPX) levels in patients with AR. Furthermore, the blood eosinophils obtained from the moderate-severe patients exhibited a higher potential of releasing ECP and EPX induced by CCL11 and of promoting Th2 responses than those from the mild patients and healthy controls. In conclusion, patients with moderate-severe AR are characterized by elevated levels of activated and pathogenic eosinophils, which are associated with higher production of ECP, EPX, and IL-4 in the peripheral blood.

Diffusion Mapping of Eosinophil-Activation State

Eosinophils are granular leukocytes that play a role in mediating inflammatory responses linked to infection and allergic disease. Their activation during an immune response triggers spatial reorganization and eventual cargo release from intracellular granules. Understanding this process is important in diagnosing eosinophilic disorders and in assessing treatment efficacy; however, current protocols are limited to simply quantifying the number of eosinophils within a blood sample. Given that high optical absorption and scattering by the granular structure of these cells lead to marked image features, the physical changes that occur during activation should be trackable using image analysis. Here, we present a study in which imaging flow cytometry is used to quantify eosinophil activation state, based on the extraction of 85 distinct spatial features from dark-field images formed by light scattered orthogonally to the illuminating beam. We apply diffusion mapping, a time inference method that orders cells on a trajectory based on similar image features. Analysis of exogenous cell activation using eotaxin and endogenous activation in donor samples with elevated eosinophil counts shows that cell position along the diffusion-path line correlates with activation level (99% confidence level). Thus, the diffusion mapping provides an activation metric for each cell. Assessment of activated and control populations using both this spatial image-based, activation score and the integrated side-scatter intensity shows an improved Fisher discriminant ratio rd = 0.7 for the multivariate technique compared with an rd = 0.47 for the traditional whole-cell scatter metric. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

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

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

Siglec-8 antibody reduces eosinophils and mast cells in a transgenic mouse model of eosinophilic gastroenteritis

Aberrant accumulation and activation of eosinophils and potentially mast cells (MCs) contribute to the pathogenesis of eosinophilic gastrointestinal diseases (EGIDs), including eosinophilic esophagitis (EoE), gastritis (EG), and gastroenteritis (EGE). Current treatment options, such as diet restriction and corticosteroids, have limited efficacy and are often inappropriate for chronic use. One promising new approach is to deplete eosinophils and inhibit MCs with a monoclonal antibody (mAb) against sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8), an inhibitory receptor selectively expressed on MCs and eosinophils. Here, we characterize MCs and eosinophils from human EG and EoE biopsies using flow cytometry and evaluate the effects of an anti-Siglec-8 mAb using a potentially novel Siglec-8-transgenic mouse model in which EG/EGE was induced by ovalbumin sensitization and intragastric challenge. MCs and eosinophils were significantly increased and activated in human EG and EoE biopsies compared with healthy controls. Similar observations were made in EG/EGE mice. In Siglec-8-transgenic mice, anti-Siglec-8 mAb administration significantly reduced eosinophils and MCs in the stomach, small intestine, and mesenteric lymph nodes and decreased levels of inflammatory mediators. In summary, these findings suggest a role for both MCs and eosinophils in EGID pathogenesis and support the evaluation of anti-Siglec-8 as a therapeutic approach that targets both eosinophils and MCs.

Clinical and Biological Markers in Hypereosinophilic Syndromes

Hypereosinophilic syndromes (HES) are rare, heterogeneous syndromes characterized by markedly elevated eosinophil counts in the blood and/or tissue and evidence of eosinophil-associated pathology. Although parasitic infections, drug hypersensitivity, and other disorders of defined etiology can present as HES (associated HES), treatment is directed at the underlying cause rather than the eosinophilia itself. A number of additional subtypes of HES have been described, based on clinical and laboratory features. These include (1) myeloid HES—a primary disorder of the myeloid lineage, (2) lymphocytic variant HES—eosinophilia driven by aberrant or clonal lymphocytes secreting eosinophil-promoting cytokines, (3) overlap HES—eosinophilia restricted to a single organ or organ system, (4) familial eosinophilia—a rare inherited form of HES, and (5) idiopathic HES. Since clinical manifestations, response to therapy, and prognosis all differ between HES subtypes, this review will focus on clinical and biological markers that serve as markers of disease activity in HES (excluding associated HES), including those that are likely to be useful only in specific clinical subtypes.

Inflammation in Respiratory Allergy Treated by Sublingual Immunotherapy

The most common allergic diseases, such as rhinitis, asthma and atopic dermatitis, are sustained by allergic inflammation, the treatment of which requires anti-inflammatory activity. Among the available treatments, allergen immunotherapy (IT) has a documented impact on allergic inflammation which persists after its discontinuation and modifies the natural course of allergy. The anti-inflammatory effects of IT, and particularly of sublingual IT (SLIT), are based on the ability to modify the phenotype of T cells which, in allergic subjects, are characterized by a prevalence of the Th2 type, with production of IL-4, IL-5, IL-13, IL-17, and IL-32 cytokines. IT-induced changes result in a Th1-type response (immune deviation) related to an increased IFN-gamma and IL-2 production or in a Th2 reduced activity, through a mechanism of anergy or tolerance. It is now known that T cell tolerance is characterized by the generation of allergen-specific Treg cells, which produce cytokines such as IL-10 and TGF-beta with immunosuppressant and/or immunoregulatory activity. Recent studies suggest that the anti-inflammatory mechanism of SLIT is similar to classical, subcutaneous IT, with a prominent role in SLIT for mucosal dendritic cells. The tolerance pattern induced by Treg accounts for the suppressed or reduced activity of inflammatory cells and for the isotypic switch of antibody synthesis from IgE to IgG, and especially to IgG4. Data obtained from biopsies clearly indicate that the pathophysiology of the oral mucosa plays a pivotal role in inducing tolerance to the sublingually administered allergen.

Sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8) is an activating receptor mediating β2-integrin-dependent function in human eosinophils

BACKGROUND

Siglec-8 is a CD33 subfamily cell-surface receptor selectively expressed on human eosinophils. After cytokine priming, Siglec-8 mAb or glycan ligand binding causes eosinophil apoptosis associated with reactive oxygen species (ROS) production. Most CD33-related Siglecs function as inhibitory receptors, but the ability of Siglec-8 to stimulate eosinophil ROS production and apoptosis suggests that Siglec-8 might instead function as an activating receptor.

OBJECTIVE

We sought to determine the role of IL-5 priming and identify the signaling molecules involved in Siglec-8 function for human eosinophils.

METHODS

We used an mAb and/or a multimeric synthetic sulfated sialoglycan ligand recognizing Siglec-8 in combination with integrin blocking antibodies, pharmacologic inhibitors, phosphoproteomics, and Western blot analysis to define the necessity of various proteins involved in Siglec-8 function for human eosinophils.

RESULTS

Cytokine priming was required to elicit the unanticipated finding that Siglec-8 engagement promotes rapid β₂-integrin-dependent eosinophil adhesion. Also novel was the finding that this adhesion was necessary for subsequent ROS production and apoptosis. Siglec-8-mediated ROS was generated through reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation because pretreatment of eosinophils with catalase (an extracellular superoxide scavenger) or NSC 23766 (a Rac GTPase inhibitor) completely inhibited Siglec-8-mediated eosinophil apoptosis. Finally, engagement of Siglec-8 on IL-5-primed eosinophils resulted in increased phosphorylation of Akt, p38, and c-Jun N-terminal kinase 1 that was also β₂-integrin dependent; pharmacologic inhibition of these kinases completely prevented Siglec-8-mediated eosinophil apoptosis.

CONCLUSIONS

These data demonstrate that Siglec-8 functions uniquely as an activating receptor on IL-5-primed eosinophils through a novel pathway involving regulation of β₂-integrin-dependent adhesion, NADPH oxidase, and a subset of protein kinases.

IL-33 restricts tumor growth and inhibits pulmonary metastasis in melanoma-bearing mice through eosinophils

The alarmin IL-33 is an IL-1 family member that stimulates pleiotropic immune reactions depending on the target tissue and microenvironmental factors. In this study, we have investigated the role of IL-33/ST2 axis in antitumor response to melanoma. Injection of IL-33 in mice-bearing subcutaneous B16.F10 melanoma resulted in significant tumor growth delay. This effect was associated with intratumoral accumulation of CD8⁺ T cells and eosinophils, decrease of immunosuppressive myeloid cells, and a mixed Th1/Th2 cytokine expression pattern with local and systemic activation of CD8⁺ T and NK cells. Moreover, intranasal administration of IL-33 determined ST2-dependent eosinophil recruitment in the lung that prevented the onset of pulmonary metastasis after intravenous injection of melanoma cells. Accordingly, ST2-deficient mice developed pulmonary metastasis at higher extent than wild-type counterparts, associated with lower eosinophil frequencies in the lung. Of note, depletion of eosinophils by in vivo treatment with anti-Siglec-F antibody abolished the ability of IL-33 to both restrict primary tumor growth and metastasis formation. Finally, we show that IL-33 is able to activate eosinophils resulting in efficient killing of target melanoma cells, suggesting a direct antitumor activity of eosinophils following IL-33 treatment. Our results advocate for an eosinophil-mediated antitumoral function of IL-33 against melanoma, thus opening perspectives for novel cancer immunotherapy strategies.

Serum biomarkers for allergy in children

A large number of studies investigating various biomarkers for allergy have been published over the past decades. The aim of this review was to evaluate these biomarkers on their diagnostic and/or predictive value. To this date, no single or specific biomarker for allergy has been identified. As allergy is not one disease, but a collection of a number of allergic conditions, it is more plausible a combination of clinical history, clinical readouts, and diagnostic markers will be needed.

Novel Therapies for Eosinophilic Disorders

Current therapies for eosinophilic disorders are limited. Most treatment approaches remain empirical, are not supported by data from controlled clinical trials, involve the off-label use of agents developed for treatment of other diseases, and tend to rely heavily on the use of glucocorticoids and other agents with significant toxicity. Great progress has been made in the discovery, preclinical development, and clinical testing of a variety of biologics and small molecules that have the potential to directly or indirectly influence eosinophils, eosinophilic inflammation, and the consequences of eosinophil activation.

Interleukin-5 pathway inhibition in the treatment of eosinophilic respiratory disorders: evidence and unmet needs

PURPOSE OF REVIEW

Human eosinophils were first identified and named by Paul Ehrlich in 1879 on the basis of the cell's granular uptake of eosin. Although eosinophils represent approximately 1% of peripheral blood leukocytes, they have the propensity to leave the blood stream and migrate into inflamed tissues. Eosinophils and their mediators are critical effectors to asthma and eosinophilic granulomatosis with polyangiitis (EGPA). Eosinophils are equipped with a large number of cell-surface receptors and produce specific cytokines and chemokines.

RECENT FINDINGS

Eosinophils are the major source of interleukin-5 and highly express the interleukin-5Rα on their surface. Clinical trials evaluating monoclonal antibodies to interleukin-5 (mepolizumab and reslizumab) and its receptor interleukin-5Rα (benralizumab) have been or are underway in patients with eosinophilic asthma, EGPA and chronic obstructive pulmonary disease (COPD). Overall, targeting interleukin-5/interleukin-5Rα is associated with a marked decrease in blood and sputum eosinophilia, the number of exacerbations and improvement of some clinical parameters in adult patients with severe eosinophilic asthma. Pilot studies suggest that mepolizumab might be a glucocorticoid-sparing treatment in patients with EGPA. A preliminary study found that benralizumab did not reduce the exacerbations and did modify lung function in patients with eosinophilic COPD.

SUMMARY

The review examines recent advances in the biology of eosinophils and how targeting the interleukin-5 pathway might offer benefit to some patients with severe asthma, EGPA, and COPD. Interleukin-5/interleukin-5Rα-targeted treatments offer promises to patients with eosinophilic respiratory disorders.

Activation states of blood eosinophils in asthma

Asthma is characterized by airway inflammation rich in eosinophils. Airway eosinophilia is associated with exacerbations and has been suggested to play a role in airway remodelling. Recruitment of eosinophils from the circulation requires that blood eosinophils become activated, leading to their arrest on the endothelium and extravasation. Circulating eosinophils can be envisioned as potentially being in different activation states, including non-activated, pre-activated or 'primed', or fully activated. In addition, the circulation can potentially be deficient of pre-activated or activated eosinophils, because such cells have marginated on activated endothelium or extravasated into the tissue. A number of eosinophil surface proteins, including CD69, L-selectin, intercellular adhesion molecule-1 (ICAM-1, CD54), CD44, P-selectin glycoprotein ligand-1 (PSGL-1, CD162), cytokine receptors, Fc receptors, integrins including αM integrin (CD11b), and activated conformations of Fc receptors and integrins, have been proposed to report cell activation. Variation in eosinophil activation states may be associated with asthma activity. Eosinophil surface proteins proposed to be activation markers, with a particular focus on integrins, and evidence for associations between activation states of blood eosinophils and features of asthma are reviewed here. Partial activation of β1 and β2 integrins on blood eosinophils, reported by monoclonal antibodies (mAbs) N29 and KIM-127, is associated with impaired pulmonary function and airway eosinophilia, respectively, in non-severe asthma. The association with lung function does not occur in severe asthma, presumably due to greater eosinophil extravasation, specifically of activated or pre-activated cells, in severe disease.

Impact of allergic rhinitis and specific subcutaneous immunotherapy on peripheral blood basophils of patients sensitized to Dermatophagoides pteronyssinus

Background

Basophils are important effectors cells in allergic rhinitis (AR) since they are involved in immunoglobulin (Ig) E – mediated inflammation and in the release of pro-inflammatory mediators. Specific subcutaneous immunotherapy (SCIT) provides clear immunologic modulation in some immune cells, however its systemic effects on basophils are not well known.

Methods

Peripheral blood (PB) samples from 43 patients with allergic rhinitis mono-sensitized to Dermatophagoides pteronyssinus (Dpt) [33 of them under SCIT with allergoid Dpt extract, in maintenance dose (SCIT), with evaluation just before SCIT injection (SCIT-T0) and 4 hours later (SCIT-T4) and the other 10 Dpt allergic patients never having, in the past, undergone specific immunotherapy treatment (NSIT)], and 15 healthy age- and gender-matched controls (HG), were analyzed. For each sample, the total (t-IgE) and specific IgE (s-IgE) was performed, as well as, the relative frequency and absolute number of PB basophils and receptor-bound IgE and IgG expression were evaluated by flow cytometry and the Histamine N-methyltransferase (HNMT) and tryptase α/β1 (TPSAB1) gene expression was assessed by real-time PCR.

Results

Higher levels of receptor-bound IgE were observed in SCIT patients, which are correlated with the levels of serum t-IgE and s-IgE, whereas no significant differences were observed for receptor-bound IgG. Regarding HNMT mRNA expression, significantly lower expression levels were detected in AR patients compared to HG, independently of type of therapy. Moreover a negative correlation was found between HNMT gene expression and time under SCIT. Conversely, tryptase gene expression was significantly up-regulated in NSIT when compared to HG; however in SCIT patients, tryptase gene expression was significantly decreased than in NSIT patients. No differences were found for any parameter between SCIT-T0 and SCIT-T4 with exception of a transient increased expression of tryptase in SCIT-T4.

Conclusion

PB basophils from patients with AR show altered functional features, which seems to be influenced by SCIT, suggesting that these cells could be useful to clarify the SCIT triggered mechanisms at a systemic level.

Therapeutic targeting of eosinophil adhesion and accumulation in allergic conjunctivitis

Considerable evidence indicates that eosinophils are important effectors of ocular allergy. Increased worldwide prevalence of allergic eye pathologies has stimulated the identification of novel drug targets, including eosinophils and adhesion molecules. Accumulation of eosinophils in the eye is a key event in the onset and maintenance of allergic inflammation and is mediated by different adhesion molecules. Antihistamines with multiple mechanisms of action can be effective during the early and late phases of allergic conjunctivitis by blocking the interaction between β(1) integrins and vascular cell adhesion molecule (VCAM)-1. Small molecule antagonists that target key elements in the process of eosinophil recruitment have been identified and reinforce the validity of α(4)β(1) integrin as a therapeutic target. Glucocorticoids are among the most effective drugs for ocular allergy, but their use is limited by adverse effects. Novel dissociated glucocorticoids can prevent eosinophil accumulation and induce apoptosis of eosinophils, making them promising candidates for ophthalmic drugs. This article reviews recent understanding of the role of adhesion molecules in eosinophil recruitment in the inflamed conjunctiva along with effective treatments for allergic conjunctivitis.

Innate immune cells in liver inflammation

Innate immune system is the first line of defence against invading pathogens that is critical for the overall survival of the host. Human liver is characterised by a dual blood supply, with 80% of blood entering through the portal vein carrying nutrients and bacterial endotoxin from the gastrointestinal tract. The liver is thus constantly exposed to antigenic loads. Therefore, pathogenic microorganism must be efficiently eliminated whilst harmless antigens derived from the gastrointestinal tract need to be tolerized in the liver. In order to achieve this, the liver innate immune system is equipped with multiple cellular components; monocytes, macrophages, granulocytes, natural killer cells, and dendritic cells which coordinate to exert tolerogenic environment at the same time detect, respond, and eliminate invading pathogens, infected or transformed self to mount immunity. This paper will discuss the innate immune cells that take part in human liver inflammation, and their roles in both resolution of inflammation and tissue repair.

Pathogenesis and classification of eosinophil disorders: a review of recent developments in the field

Eosinophils and their products play an essential role in the pathogenesis of various reactive and neoplastic disorders. Depending on the underlying disease, molecular defect and involved cytokines, hypereosinophilia may develop and may lead to organ damage. In other patients, persistent eosinophilia is accompanied by typical clinical findings, but the causative role and impact of eosinophilia remain uncertain. For patients with eosinophil-mediated organ pathology, early therapeutic intervention with agents reducing eosinophil counts can be effective in limiting or preventing irreversible organ damage. Therefore, it is important to approach eosinophil disorders and related syndromes early by using established criteria, to perform all appropriate staging investigations, and to search for molecular targets of therapy. In this article, we review current concepts in the pathogenesis and evolution of eosinophilia and eosinophil-related organ damage in neoplastic and non-neoplastic conditions. In addition, we discuss classifications of eosinophil disorders and related syndromes as well as diagnostic algorithms and standard treatment for various eosinophil-related disorders.

Controversies and open questions in the definitions and classification of the hypereosinophilic syndromes and eosinophilic leukemias

Eosinophilia is frequently detectable in certain myeloid neoplasms and various reactive conditions, but it may also occur in the absence of an apparent underlying disease, or, rarely, as a paraneoplastic feature with solid tumors. In myeloid neoplasms, eosinophils are considered to belong to the malignant clone in most cases, whereas in all other conditions, eosinophilia is a reactive process triggered by eosinopoietic cytokines. Excessive accumulation of eosinophils, also termed hypereosinophilia (HE), is typically seen in eosinophilic leukemias, but it may also occur in other neoplasms and reactive disorders. HE-related end organ damage may develop in patients with reactive HE but also in those with hematologic malignancies. During the past few years, our knowledge about HE and HE-related organ damage in hematologic and nonhematologic disorders has improved considerably. Moreover, proposals for the definition and classification of eosinophil disorders have been generated by various expert groups and by the World Health Organization (WHO). However, several questions related to eosinophils and HE remain open, and many aspects of the definition and classification of eosinophil disorders and related pathologies remain controversial. In the current article, these open issues are discussed with special reference to the 2008 WHO classification of myeloid neoplasms and other classifications proposed by immunologists and various expert panels, as well as definitions and criteria recently proposed in a multidisciplinary consensus proposal.

Eosinophils: multifaceted biological properties and roles in health and disease

Eosinophils are leukocytes resident in mucosal tissues. During T-helper 2 (Th2)-type inflammation, eosinophils are recruited from bone marrow and blood to the sites of immune response. While eosinophils have been considered end-stage cells involved in host protection against parasite infection and immunopathology in hypersensitivity disease, recent studies changed this perspective. Eosinophils are now considered multifunctional leukocytes involved in tissue homeostasis, modulation of adaptive immune responses, and innate immunity to certain microbes. Eosinophils are capable of producing immunoregulatory cytokines and are actively involved in regulation of Th2-type immune responses. However, such new information does not preclude earlier observations showing that eosinophils, in particular human eosinophils, are also effector cells with proinflammatory and destructive capabilities. Eosinophils with activation phenotypes are observed in biological specimens from patients with disease, and deposition of eosinophil products is readily seen in the affected tissues from these patients. Therefore, it would be reasonable to consider the eosinophil a multifaceted leukocyte that contributes to various physiological and pathological processes depending on their location and activation status. This review summarizes the emerging concept of the multifaceted immunobiology of eosinophils and discusses the roles of eosinophils in health and disease and the challenges and perspectives in the field.

Distinctive blood eosinophilic phenotypes and cytokine patterns in eosinophilic esophagitis, inflammatory bowel disease and airway allergy

Blood eosinophil numbers may be elevated in allergy, inflammatory bowel disease and eosinophilic esophagitis. The aim of this study was to examine whether circulating eosinophils display distinct phenotypes in these disorders and if different patterns of eosinophilic chemoattractants exist. Blood eosinophils from patients with symptomatic eosinophilic esophagitis (EoE; n = 12), ulcerative colitis (n = 8), airway allergy (n = 10) and healthy controls (n = 10) were enumerated and their surface markers analyzed by flow cytometry. Plasma levels of pro-eosinophilic cytokines were quantified in parallel. Data were processed by multivariate pattern recognition methods to reveal disease-specific patterns of eosinophil phenotypes and cytokines. EoE patients had higher numbers of eosinophils with enhanced expression of CD23, CD54, CRTH2 and CD11c and diminished CCR3 and CD44 expression. Plasma CCL5 was also increased in EoE. Although allergic patients had increased interleukin (IL)-2, IL-3, IL-5 and granulocyte macrophage colony-stimulating factor plasma concentrations, their blood eosinophil phenotypes were indistinguishable from those of healthy controls. Decreased eosinophilic expression of CD11b, CD18, CD44 and CCR3, but no distinctive pattern of eosinophil chemoattractants, characterized ulcerative colitis. We propose that eosinophils acquire varying functional properties as a consequence of distinct patterns of activation signals released from the inflamed tissues in different diseases.

The histamine H4 receptor is highly expressed on plasmacytoid dendritic cells in psoriasis and histamine regulates their cytokine production and migration

Plasmacytoid dendritic cells (pDC) are present in inflammatory skin lesions, in particular, in psoriasis. In such lesions, the inflammatory mediator histamine is also detected in high amounts. We therefore investigated a possible interaction of pDC with histamine, especially via the most recently described histamine H(4) receptor (H(4)R). We detected the expression of the H(4)R on pDC in the blood and in lesional psoriasis skin. Interestingly, compared with healthy controls and patients with atopic dermatitis, pDC from the blood of psoriasis patients expressed the highest levels of the H(4)R, which was even more upregulated on stimulation with IFN-γ and CpG. After activation of the H(2)R and H(4)R on pDC, we observed downregulation of CpG-induced production of tumor necrosis factor α, IFN-α, and CXCL8, but not of the chemokine CXCL10. Histamine-induced downregulation of cytokine production was more pronounced in pDC derived from psoriasis patients. Furthermore, we observed F-actin polymerization and active migration of pDC in response to H(4)R agonist stimulation. Taken together, our results indicate that the H(4)R is highly expressed on pDC in psoriasis and influences cytokine production and migration of pDC. Therefore, the H(4)R alone or in combination with the H(2)R might be a promising therapeutic target in psoriasis.

Public facility workers' immunological characteristics involved with development of respiratory allergic diseases in Korea

We evaluated the immuno-pulmonary status of employees working at public facilities to determine whether they are at greater risk of developing respiratory allergies. Fifty-two employees from child daycare centers, elderly nursing homes, subway stations, and hypermarkets, and 17 office workers were recruited. All were subjected to a skin prick test (SPT) for 25 aeroallergens and the methacholine bronchial challenge test. Various immunological parameters, including plasma IgE and IgG4 levels, hematology parameters, and in vitro cytokine production from peripheral T cells, were assessed. Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were also determined. Of the facility employees, 54% responded to the SPT, and house dust mite induced positive skin reactions most frequently. Compared to the SPT-negative facility employees and the office workers, the SPT-positive facility employees had upregulated plasma IgE levels and eosinophil frequency in their peripheral blood. Their peripheral T cells also showed elevated IL-4 production relative to IFNgamma production. Four public facility employees who reacted to the methacholine challenge test had elevated eosinophil frequencies, increased plasma IgE levels, and lowered FEV1/FVC values. This study suggests that workers at public facilities could show greater risk towards the development of respiratory allergic diseases.

Eosinophilia and thrombosis in parasitic diseases: an overview

It is known that peripheral blood eosinophilia (PBE) is a normal hematopoietic response to several parasitic diseases, but it is less known that PBE promotes a hypercoagulable state that may favor thrombosis. Scope of this article is to explore which parasitic infestations are most likely to be complicated by thrombosis and to highlight the pathogenetic contribution of PBE to vascular occlusions in this setting. A review of the world literature revealed 18 cases in which PBE was associated with vascular occlusion though no specific surveys were dedicated to this topic. The eosinophil exerts its thrombogenic potential by inhibition of the natural anticoagulant pathways and release of tissue factor with enhanced coagulation activation leading to vascular occlusion. It is hoped that this review contributes to the awareness of the link between PBE and thrombosis in parasitic disorders to foster research in this area.

Diagnostic value of the basophil activation test in evaluating Hymenoptera venom sensitization

BACKGROUND

Diagnosis of allergy to Hymenoptera venom is usually confirmed with skin testing and measurement of specific serum IgE antibody, tests which are sometimes inconclusive. In these cases, additional in vitro tests are necessary. The aim of this study was to show the applicability of the basophil activation test in detecting sensitization to Hymenoptera venom and to compare the test sensitivity and clinical positive-predictive value with skin prick tests and measurement of allergen-specific serum IgE.

METHODS

This prospective study was conducted between June 2004 and December 2007 and included a large group of 204 patients. All patients had a history of at least one systemic allergic reaction of Müller grades II-IV after a Hymenoptera sting. We compared results of the basophil activation test, specific serum IgE and skin prick tests with patients' clinical history and data on culprit insects.

RESULTS

The overall clinical sensitivities of the basophil activation test, specific serum IgE and skin prick tests were 90%, 76% and 64%, respectively; the clinical positive-predictive values of the three tests were 79%, 73% and 78% for bee venom, 86%, 59% and 43% for wasp venom; and 84%, 77% and 22% for both venoms.

CONCLUSIONS

Our results revealed a higher clinical sensitivity and comparable or better clinical positive-predictive value of basophil activation tests than skin prick tests and allergen-specific serum IgE in the detection of allergy to Hymenoptera venom.

Necator americanus infection: a possible cause of altered dendritic cell differentiation and eosinophil profile in chronically infected individuals

BACKGROUND

Hookworms survive for several years (5 to 7 years) in the host lumen, inducing a robust but largely ineffective immune response. Among the most striking aspects of the immune response to hookworm (as with many other helminths) is the ablation of parasite-specific T cell proliferative response (hyporesponsiveness). While the role of the adaptive immune response in human helminth infection has been well investigated, the role of the innate immune responses (e.g., dendritic cells and eosinophils) has received less attention and remains to be clearly elucidated.

METHODOLOGY/PRINCIPAL FINDINGS

We report on the differentiation/maturation of host dendritic cells in vitro and the eosinophil activation/function associated with human hookworm infection. Mature DCs (mDCs) from Necator americanus (Necator)-infected individuals showed an impaired differentiation process compared to the mDCs of non-infected individuals, as evidenced by the differential expression of CD11c and CD14. These same hookworm-infected individuals also presented significantly down-regulated expression of CD86, CD1a, HLA-ABC, and HLA-DR. The lower expression of co-stimulatory and antigen presentation molecules by hookworm-infected-derived mDCs was further evidenced by their reduced ability to induce cell proliferation. We also showed that this alternative DC differentiation is partially induced by excreted-secreted hookworm products. Conversely, eosinophils from the same individuals showed a highly activated status, with an upregulation of major cell surface markers. Antigen-pulsed eosinophils from N. americanus-infected individuals induced significant cell proliferation of autologous PBMCs, when compared to non-infected individuals.

CONCLUSION

Chronic N. americanus infection alters the host's innate immune response, resulting in a possible modulation of the maturation process of DCs, a functional change that may diminish their ability for antigen presentation and thus contribute to the ablation of the parasite-specific T cell proliferative response. Interestingly, a concomitant upregulation of the major cell surface markers of eosinophils was observed in hookworm-infected individuals, indicative of antigen-specific immune responses, especially antigen presentation. We showed that in addition to the postulated role of the eosinophils as effector cells against helminth infection, activated cells may also be recruited to sites of inflammation and contribute to the immune response acting as antigen presenting cells.

Human basophils and cytokines/chemokines

Basophils comprise the smallest population in human peripheral blood leukocytes. The role of basophils in the pathogenesis of allergic diseases has long been obscure, although their accumulation and activation in tissues have suggested their potential importance. Recent advances in the field of basophil biology have indicated that cytokines and chemokines are the primary regulators of basophil functions. In addition, various functions of these cells seem differently modulated. The evidence strongly supports the notion that basophils exposed to these substances and allergens will behave as unique effector cells that presumably play proinflammatory roles in type I allergic reactions.

Eosinophil activation status, cytokines and liver fibrosis in Schistosoma mansoni infected patients

We have been investigating whether human eosinophils play an important role in schistosomiasis mansoni morbidity. Our main focus has been on the activation-related cell surface markers (CD23/CD69/CD25/HLA-DR/CD28/CD80) and the detection of TNF-alpha, IL-4 and IL-5 in peripheral blood eosinophils from chronic Schistosoma mansoni-infected patients. Our studies compare both, intestinal (INT) and individuals with periportal fibrosis (FIB). Our major findings, point to distinct profile of activation-related surface markers on eosinophils as the hallmark of disease morbidity during chronic S. mansoni infection. Up-regulation of several activation-related markers was observed on eosinophils from FIB group, but not INT, which include early activation markers, such as CD69 and CD23. INT displayed a distinct profile, with up-regulation of molecules related to the late activation (CD25, HLA-DR, CD28 and CD80). These results suggest that some immunoregulatory events may take place controlling the early eosinophil activation in the INT group. Higher levels of eosinophil-derived cytokines were observed in FIB, regardless the antigen stimulation in vitro. A mixed cytokine pattern, characterized by positive correlation between TNF-alpha, IL-4 and IL-5 was observed in both INT and FIB. However, lack of correlation between the cytokine expression and the eosinophil activation status points out that even those FIB patients presenting minor increment on eosinophil activation displayed higher levels of cytokine-positive eosinophils. Indeed, the positive association between lymphocyte-derived IL-10 and the eosinophils cytokine profile was observed exclusively in INT further emphasize our hypothesis that immunoregulatory events take place controlling disease morbidity in human schistosomiasis. The impaired IL-10-driven immunoregulatory function may play an important role on the establishment of pathology in patients bearing periportal fibrosis.

Progress in allergy signal research on mast cells: systemic approach to mast cell biology in allergic diseases

At the end of the last century, microarray technology that examines the total genes and transcripts present in a cell became available as a laboratory tool. Mast cells are known to play a pivotal role in initiating allergic inflammation by releasing various mediators and cytokines. According to the recent microarray-based studies, mast cells have been found to be much more versatile functional molecules than we ever thought. Also, genes that are exclusively expressed in mast cells have been identified in comparison with other cell types. In this article, the outcome of microarray-based analyses on the role of mast cells in allergic inflammation will be reviewed by focusing on the mast cell-specific genes as drug targets.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Interleukin-3 promotes the expression of E-NPP3/CD203C on human blood basophils in healthy subjects and in patients with birch pollen allergy

We recently identified the ectoenzyme CD203c as a novel basophil activation antigen that is upregulated in response to FcepsilonRI cross-linkage. We investigated the effects of various interleukins (ILs) on expression of CD203c on blood basophils using an antibody against CD203c and flow cytometry. Of all cytokines tested, only IL-3 was found to upregulate expression of CD203c on basophils above baseline levels. The effects of IL-3 were dose- and time-dependent (EC(50): 0.1-1 ng/ml) without differences observed between healthy and allergic donors. Whereas anti-IgE induced maximum upregulation of CD203c within 15 minutes, the IL-3-induced upregulation showed a maximum after 180 minutes. IgE-receptor cross-linking resulted in enhanced expression of both CD63 and CD203c, whereas IL-3 enhanced the levels of CD203c without promoting expression of CD63. The IL-3-induced upregulation of CD203c was also observed in highly enriched basophils and was counteracted by a blocking antibody against the alpha chain of the IL-3 receptor (CD123). The IL-3-induced upregulation of CD203c was also found to depend on the presence of calcium. To analyze signaling pathways involved in IL-3-induced upregulation of CD203c, pharmacologic inhibitors were applied. The PI3-kinase inhibitors, wortmannin and LY294002 counteracted the IL-3-induced expression of CD203c, whereas MEK- and PKC inhibitors showed no effects. In conclusion, IL-3 upregulates expression of CD203c on basophils through a specific receptor and via a PI3-kinase-dependent signaling-pathway. Compared to FcepsilonRI-mediated cell activation, IL-3-induced upregulation of CD203c is a late(r) event and is not accompanied by upregulation of CD63.

Expression of activated Fc gamma RII discriminates between multiple granulocyte-priming phenotypes in peripheral blood of allergic asthmatic subjects

BACKGROUND

Allergic asthma is associated with chronic airway and systemic immune responses. Systemic responses include priming of peripheral blood eosinophils, which is enhanced after allergen challenge. In a subpopulation of asthmatic subjects, neutrophils are associated with bronchial inflammation.

OBJECTIVE

We sought to monitor systemic granulocyte priming in allergic asthmatic subjects as a consequence of chronic and acute inflammatory signals initiated by allergen challenge.

METHODS

Blood was taken at baseline and 6 to 24 hours after allergen challenge in asthmatic subjects with and without late asthmatic responses. Systemic granulocyte priming was studied by using expression of cellular markers, such as alpha-chain of Mac-1 (alpha m)/CD11b, L-selectin/CD62L, and an activation epitope present on Fc gamma RII/CD32 recognized by monoclonal phage antibody A17.

RESULTS

Eosinophils of asthmatic subjects have a primed phenotype identified by cell-surface markers. Neutrophils of these patients were subtly primed, which was only identified after activation with N-formyl-methionyl-leucyl-phenylalanine. After allergen challenge, an acute increase in eosinophil priming characterized by enhanced expression of activated Fc gamma RII was found in patients experiencing a late asthmatic response and not in patients with a single early asthmatic response. In contrast, expression of alpha m/CD11b and L-selectin on granulocytes was not different between control and asthmatic subjects and was not affected by allergen challenge. Interestingly, expression of both adhesion molecules was positively correlated, and alpha m expression on eosinophils and neutrophils correlated positively with bronchial hyperresponsiveness.

CONCLUSION

Different phases, phenotypes, or both of allergic asthma are associated with distinct priming profiles of inflammatory cells in peripheral blood.

CLINICAL IMPLICATIONS

Insight in differences of systemic innate responses will lead to better definition of asthma subtypes and to better designs of new therapeutic options.

IgE- and FcepsilonRI-mediated enhancement of surface CD69 expression in basophils: role of low-level stimulation

Surface-expressed CD69 is a recently recognized activation marker for basophils and is reported to be strongly induced in vitro by IL-3. In this study, we investigated whether IgE- and high-affinity receptor for IgE (FcepsilonRI)-dependent stimuli can affect basophil CD69 expression. Highly purified basophils were cultured for 24 h in the presence of anti-FcepsilonRI alpha-chain mAb, CRA-1 and IL-3, and surface CD69 expression was analyzed by flow cytometry. CRA-1 mAb at 1 ng/ml or lower concentrations, levels too low to provoke direct histamine release, dose-dependently enhanced surface CD69 expression in the presence of IL-3, although low-dose CRA-1 mAb failed to induce CD69 expression in the absence of IL-3. Recombinant Der f 2 at 10 to 100 pg/ml enhanced CD69 levels in the presence of IL-3 in basophils from mite-sensitive subjects. These results suggest that allergens may influence basophil CD69 expression even when the levels of the antigens are too low to trigger direct degranulation. Upregulated CD69 expression on locally accumulated basophils in bronchial asthma may be attributed at least in part to a combination of local cytokines, especially IL-3, plus exposure to low levels of IgE-crosslinking allergens.

The NR4A nuclear receptor family in eosinophils

It is well-known that many members of the family of nuclear receptors have been implicated in human diseases, and metabolic disorders in particular. The NR4A nuclear receptor family consists of three members, Nur77, Nurr1, and NOR1. All of these are orphan receptors, and Nur77 and NOR1 exert possible pathological roles in immune diseases through the modulation of leukocyte functions. CD30 stimulation, which induces eosinophil-specific apoptosis, markedly enhances expression of Nur77 and NOR1 in eosinophils. This suggests the possibility of pharmacological modulation of Nur77- or NOR1-specific apoptotic pathways via receptor-dependent transactivation. In this review, we discuss treatment of allergic diseases by low molecular weight compounds acting through the NR4A receptor family to cause eosinophil apoptosis. NR4A nuclear receptor genes were selected following comprehensive analysis of differentially expressed genes in eosinophils of atopic dermatitis patients compared with healthy volunteers.

Flow-assisted allergy diagnosis: current applications and future perspectives

Physicians predominantly rely upon quantification of serum-specific immunoglobulin E (IgE) and/or skin test to confirm clinically suspected IgE-mediated allergy. However, for various reasons, identification of the offending allergen(s) and potentially cross-reactive structures is not always straightforward. Flow-assisted allergy diagnosis relies upon quantification of alterations in the expression of particular basophilic activation markers. Actually, upon challenge with a specific allergen, basophils not only secrete quantifiable bioactive mediators but also upregulate the expression of different markers which can be detected efficiently by flow cytometry using specific monoclonal antibodies. Currently, the technique has been applied in the investigation of IgE-mediated allergy caused by classical inhalant allergens, food, Hevea latex, hymenoptera venoms and drugs. It is also appreciated; the technique proves valuable in the diagnosis of non-IgE-mediated (anaphylactoid) reactions such drug hypersensitivity and the detection of autoantibodies in certain forms of chronic urticaria. This review will not address immunologic features, characteristics and general pitfalls of flow-assisted analysis of in vitro-activated basophils as summarized elsewhere. After a recapitulation of the principles and some specific technical issues of flow-assisted analysis of in vitro-activated basophils, we principally focus on the current clinical and research applications of the basophil activation tests. Personal experience of both research groups is provided, where appropriate. Finally, a viewpoint on how the field might evolve in the following years is provided.

Disturbance mechanisms of eosinophils’ and immunocytes’ cooperation in the forming large blood eosinophilias

Data of modern literature and results of own investigations concerning the role of imbalance of immune-regulatory cytokines’ system in the mechanisms of forming severe eosinophilias of blood in pathologic processes of different genesisare analyzed in the article

Systemic eosinophil response induced by respiratory syncytial virus

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract disease (LRTD) in infants. Eosinophils have been suggested to play a role in the disease pathogenesis of LRTD. Inflammation can induce functional and morphological alterations of peripheral blood granulocytes. In patients with RSV LRTD, we aimed to investigate the eosinophil activation status by analysing surface markers. In vitro stimulation of eosinophils with cytokines leads to up-regulation of CD11b and priming markers recognized by the recently developed priming markers A17 and A27, whereas interleukin (IL)-5Ralpha is being down-regulated. In 51 patients and 10 controls we examined the expression of these surface markers on eosinophils in moderate to severe RSV-induced LRTD patients at the time of admission and 6 weeks later during the convalescence phase. RSV-patients were characterized by a higher eosinophil CD11b expression compared to controls. Although basal A17 and A27 expression was not increased, we observed a significantly higher expression of these priming epitopes on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated cells of RSV patients compared with cells of controls, indicative of prior in vivo priming. Furthermore, IL-5Ralpha expression was down-regulated on peripheral blood eosinophils of these patients. Follow-up blood samples showed normalization of all markers but CD11b, which was persistently increased. Utilizing cellular markers, we observed that peripheral blood eosinophils from infants with RSV LRTD are in a more activated state compared to eosinophils of controls, which normalizes only partially during convalescence.

Evaluation of basophil activation in food allergy: present and future applications

PURPOSE OF REVIEW

The diagnosis of immediate hypersensitivity relies on specific IgE and history. Because of low specificity, however, provocation challenges are often necessary. Furthermore, IgE testing does not predict features such as reaction severity; nor can it discriminate cross-reactivity from multiple sensitizations. Direct and passive basophil activation tests may address these needs. In addition, measuring basophil activation ex vivo may be useful for monitoring patients with food allergies.

RECENT FINDINGS

Several papers using basophil activation tests demonstrate comparable sensitivity and specificity to current testing for food allergy. Flow-based basophil activation tests have also been used to assess functional characteristics of patient IgE. Finally, several activation phenotypes have been identified as markers of allergic inflammation in vivo; these phenotypes appear to correspond to earlier reports of spontaneous histamine-releasing basophils in patients with active allergic inflammation.

SUMMARY

Although in their early stages, direct basophil activation tests may prove to be useful in the clinic. Indirect basophil activation studies are useful when applied to compare functional aspects of IgE. Identification of basophil activation ex vivo is a promising approach for monitoring allergic inflammation.