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With the development of targeted therapies for allergic diseases, the need for biomarkers supporting disease diagnosis and management has increased. Recent research has elucidated the pattern of cytokines and their distinct roles in the pathogenesis of allergic diseases. This means that cytokines should be considered as biomarkers. In this review article, we summarize published findings and critically discuss the use of cytokine measurements in association with disease diagnosis and management. Among the variety of suggested cytokines, thymus and activation-regulated chemokine (TARC) stands out and can indeed serve as a biomarker of atopic dermatitis. Both biologic characteristics and technical issues determine the reliability and limit the use of blood cytokines as biomarkers., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Chronic rhinosinusitis (CRS) often is characterized by an eosinophilic inflammatory pattern, nowadays referred to as type 2 inflammation, although the mucosal inflammation is dominated by neutrophils in about a third of the patients. Neutrophils are typically predominant in 50% of patients with CRS without nasal polyps, but also are found to play a role in patients with severe type 2 CRS with nasal polyp disease. This review aims at summarizing the current understanding of the eosinophilic and neutrophilic inflammation in CRS pathophysiology, and provides a discussion of their reciprocal interactions and the clinical impact of the mixed presentation in patients with severe type 2 CRS with nasal polyps. A solid understanding of these interactions is of utmost importance when treating uncontrolled severe CRS with nasal polyps with biologicals that are preferentially directed toward type 2 inflammation. We here focus on recent findings on both eosinophilic and neutrophilic granulocytes, their subgroups and the activation status, and their interactions in CRS., (Copyright © 2021 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Eosinophils are a subset of granulocytes that can be involved in the pathogenesis of different diseases, including allergy. Their effector functions are closely linked to their cytotoxic granule proteins. Release takes place through several different mechanisms, one of which is cytolysis, which is associated with release of intact granules, so-called clusters of free eosinophil granules. The mechanism underlying this activation-induced form of cell death in eosinophils has remained unclear., Objective: We aimed to elucidate the molecular mechanism of eosinophil cytolysis., Methods: Isolated blood eosinophils were incubated on glass coverslips coated with intravenous immunoglobulin and inactive complement component 3b. A morphologic characterization of the distinct stages of the proposed cascade was addressed by means of time-lapse automated fluorescence microscopy, electron microscopy, and immunohistochemistry. Experiments with pharmacologic inhibitors were performed to elucidate the sequence of events within the cascade. Tissue samples of patients with eosinophilic skin diseases or eosinophilic esophagitis were used for in vivo analyses., Results: After eosinophil adhesion, we observed reactive oxygen species production, early degranulation, and granule fusion processes, leading to a distinct morphology exhibiting cytoplasmic vacuolization and, finally, cytolysis. Using a pharmacologic approach, we demonstrate the presence of a receptor-interacting protein kinase 3 (RIPK3)-mixed lineage kinase-like (MLKL) signaling pathway in eosinophils, which, after its activation, leads to the production of high levels of reactive oxygen species in a p38 mitogen-activated protein kinase and phosphatidylinositol 3'-kinase-dependent manner. All these steps are required for cytoplasmic vacuolization and subsequent cytolysis to occur. Interestingly, triggering cytolysis is associated with an induction of autophagy in eosinophils, and additional stimulation of autophagy by means of pharmacologic inhibition of the mechanistic target of rapamycin counterregulates cell death. Moreover, MLKL phosphorylation, cytoplasmic vacuolization, and cytolysis were observed in eosinophils under in vivo inflammatory conditions., Conclusion: We report that adhesion-induced eosinophil cytolysis takes place through RIPK3-MLKL-dependent necroptosis, which can be counterregulated by autophagy., (Copyright © 2017. Published by Elsevier Inc.)

Background: Chronic rhinosinusitis with nasal polyps is characterized by T H 2-biased eosinophilic inflammation. Eosinophils have been shown to generate so-called extracellular eosinophilic traps (EETs) under similar pathologic conditions., Objective: Our aim was to investigate a possible link between EET formation and the presence of Staphylococcus aureus, an organism frequently colonizing the upper airways, at the human mucosal site of the disease., Methods: Tissue slides were investigated for the presence of EETs and S aureus by using immunofluorescent staining and the PNA-Fish assay, respectively. An ex vivo human mucosal disease tissue model was used for artificial infection with S aureus. Cell markers were analyzed by using immunohistochemistry, the Luminex Multiplex assay, ELISA, PCR, and immunoblotting and linked to the presence of EETs., Results: About 8.8% ± 4.8% of the infiltrating eosinophils exhibited EETs in patients' nasal polyp tissues. Formation of EETs was associated with increased IL-5 (P < .05) and periostin (P < .05) tissue levels and colonization with S aureus (P < .05). By using an ex vivo human mucosal disease tissue model, EET formation was induced (4.2 ± 0.9-fold) on exposure to S aureus but not Staphylococcus epidermidis. Eosinophils were shown to migrate (P < .01) toward S aureus and entrap the bacteria both inside and outside the mucosal tissue. Blocking NAPDH oxidase activity led to a complete inhibition (P < .05) of EET formation by S aureus., Conclusion: Eosinophils are likely to be specifically recruited to S aureus and possibly other microorganisms and form EETs at sites of airway epithelial damage to protect the host from infections in patients with chronic rhinosinusitis with nasal polyps., (Copyright © 2017 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Atopic dermatitis (AD) is a complex skin disease frequently associated with other diseases of the atopic diathesis. Recent evidence supports the concept that AD can also recognize other comorbidities, such as chronic inflammatory bowel or cardiovascular diseases. These comorbidities might result from chronic cutaneous inflammation or from a common, yet-to-be-defined immunologic background leading to immune deviations. The activation of immune cells and their migration to the skin play an essential role in the pathogenesis of AD. In patients with AD, an underlying immune deviation might result in higher susceptibility of the skin to environmental factors. There is a high unmet medical need to define immunologic endotypes of AD because it has significant implications on upcoming stratification of the phenotype of AD and the resulting targeted therapies in the development of precision medicine. This review article emphasizes studies on environmental factors affecting AD development and novel biological agents used in the treatment of AD. Best evidence of the clinical efficacy of novel immunologic approaches using biological agents in patients with AD is available for the anti-IL-4 receptor α-chain antibody dupilumab, but a number of studies are currently ongoing with other specific antagonists to immune system players. These targeted molecules can be expressed on or drive the cellular players infiltrating the skin (eg, T lymphocytes, dendritic cells, or eosinophils). Such approaches can have immunomodulatory and thereby beneficial clinical effects on the overall skin condition, as well as on the underlying immune deviation that might play a role in comorbidities. An effect of these immunologic treatments on pruritus and the disturbed microbiome in patients with AD has other potential consequences for treatment., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

In this consensus document we summarize the current knowledge on major asthma, rhinitis, and atopic dermatitis endotypes under the auspices of the PRACTALL collaboration platform. PRACTALL is an initiative of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology aiming to harmonize the European and American approaches to best allergy practice and science. Precision medicine is of broad relevance for the management of asthma, rhinitis, and atopic dermatitis in the context of a better selection of treatment responders, risk prediction, and design of disease-modifying strategies. Progress has been made in profiling the type 2 immune response-driven asthma. The endotype driven approach for non-type 2 immune response asthma, rhinitis, and atopic dermatitis is lagging behind. Validation and qualification of biomarkers are needed to facilitate their translation into pathway-specific diagnostic tests. Wide consensus between academia, governmental regulators, and industry for further development and application of precision medicine in management of allergic diseases is of utmost importance. Improved knowledge of disease pathogenesis together with defining validated and qualified biomarkers are key approaches to precision medicine., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Eosinophilia is an important indicator of various neoplastic and nonneoplastic conditions. Depending on the underlying disease and mechanisms, eosinophil infiltration can lead to organ dysfunction, clinical symptoms, or both. During the past 2 decades, several different classifications of eosinophilic disorders and related syndromes have been proposed in various fields of medicine. Although criteria and definitions are, in part, overlapping, no global consensus has been presented to date. The Year 2011 Working Conference on Eosinophil Disorders and Syndromes was organized to update and refine the criteria and definitions for eosinophilic disorders and to merge prior classifications in a contemporary multidisciplinary schema. A panel of experts from the fields of immunology, allergy, hematology, and pathology contributed to this project. The expert group agreed on unifying terminologies and criteria and a classification that delineates various forms of hypereosinophilia, including primary and secondary variants based on specific hematologic and immunologic conditions, and various forms of the hypereosinophilic syndrome. For patients in whom no underlying disease or hypereosinophilic syndrome is found, the term hypereosinophilia of undetermined significance is introduced. The proposed novel criteria, definitions, and terminologies should assist in daily practice, as well as in the preparation and conduct of clinical trials., (Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Eosinophils are blood cells that are often found in high numbers in the tissues of allergic conditions and helminthic parasite infections. The pathophysiologic roles that eosinophils may serve in other human "eosinophil-associated" diseases remain obscure., Objective: National Institutes of Health (NIH) Institutes and the Office of Disease Prevention assembled an international taskforce of clinical and basic scientists with the charge to propose and prioritize unmet research needs in eosinophil-associated diseases., Methods: The taskforce used an organ system approach to identify the different and common themes of eosinophil cell involvement in these diseases. In early 2012, a draft document was circulated for review. The document was amended and the prioritizations were set at a NIH-organized workshop in June 2012., Results: The taskforce identified significant research needs. These needs cross disease entities but some are disease specific. There are substantial shortcomings to the various preclinical animal models, as well as significant gaps in our epidemiologic, pathophysiologic, diagnostic, prognostic, and therapeutic knowledge. The taskforce recognized that recent efforts by patient advocacy groups have played instrumental roles in improving the identification and characterization of these disorders. However, communications among the eosinophil-interested communities, for example, governmental funding and regulatory agencies, and industry and clinician scientists need to be more comprehensive., Conclusions: Significant efforts are required to address our knowledge gaps to improve the outcomes of eosinophil-associated diseases. NIH Institutes, other federal agencies, lay organizations, and the pharmaceutical industry should consider the taskforce's recommendations in their future research activities., (Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Hypereosinophilic syndromes (HESs) are a diverse group of conditions characterized by clinical manifestations attributable to eosinophilia and eosinophilic infiltration of tissues. HESs are chronic disorders with significant morbidity and mortality. Although the availability of targeted chemotherapeutic agents, including imatinib, has improved quality of life and survival in some patients with HESs, additional agents with increased efficacy and decreased toxicity are sorely needed. The purpose of this review is to provide an overview of eosinophil biology with an emphasis on potential targets of pharmacotherapy and to provide a summary of potential eosinophil-targeting agents, including those in development, in clinical trials, or approved for other disorders., (Published by Mosby, Inc.)

Background: Asthma is a heterogeneous inflammatory airway disorder that involves eosinophilic and noneosinophilic phenotypes. Unlike in healthy lungs, eosinophils are often present in atopic asthmatic airways, although a subpopulation of asthmatic subjects predominantly experience neutrophilic inflammation. Recently, it has been demonstrated that eosinophils and neutrophils generate bactericidal extracellular traps consisting of DNA and cytotoxic granule proteins., Objective: We sought to explore whether living eosinophils and neutrophils infiltrating human atopic asthmatic airways actively form extracellular DNA traps in vivo., Methods: Quantitative analysis of eosinophils releasing DNA was performed in endobronchial biopsy specimens from 20 human subjects with mild atopic asthma at baseline and after local allergen challenge and 10 healthy subjects. DNA was stained with propidium iodine and major basic protein with specific antibody. Differential cell counts and cytokines/chemokines were assessed in bronchoalveolar lavage fluid., Results: Asthmatic airways were infiltrated with a significantly higher number of eosinophils than healthy airways (39.3 ± 4.6 vs 0.4 ± 0.9, P < .0001). All asthmatic subjects but only 1 control subject expressed eosinophils releasing DNA that colocalized with major basic protein (33.65 ± 20.33 vs 0.3 ± 0.9 per high-power field, P < .0001). Four asthmatic subjects mostly expressed neutrophilic inflammation and neutrophil DNA traps. Allergen challenge had no significant quantitative effect on eosinophil or neutrophil DNA traps. Airway eosinophils or DNA traps did not correlate with either bronchoalveolar lavage levels of IL-5, IFN-γ, or eotaxin or the provoking doses of methacholine or allergen in asthmatic subjects., Conclusions: Extracellular DNA traps are generated by eosinophils and neutrophils in human atopic asthmatic airways in vivo. The mechanism and role of this new finding will necessitate further investigation., (Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: In the skin, eosinophils are found in a broad spectrum of diseases, including infectious diseases., Objective: In this study, we investigated whether eosinophil extracellular traps, structures containing DNA in association with eosinophil granule proteins able to bind and kill bacteria, are present in the skin under various pathologic conditions., Methods: Immunofluorescence staining was performed on sections of paraformaldehyde-fixed and paraffin-embedded skin biopsy tissues of 25 different eosinophilic skin diseases by using propidium iodide and an antibody to eosinophil cationic protein. Slides were evaluated by laser scanning microscopy., Results: Eosinophils releasing DNA together with eosinophil cationic protein were detected in infectious skin diseases such as ectoparasitosis and larva migrans. Further, we observed the extracellular DNA structures in allergic/reactive diseases (Wells syndrome, hypereosinophilic syndrome, positive reaction of atopy patch test, allergic contact dermatitis, drug hypersensitivity) and in autoimmune diseases (bullous pemphigoid, pemphigus foliaceus, dermatitis herpetiformis). The average number of eosinophils releasing DNA in the skin was usually below 10%, although in Wells syndrome the proportion was up to 30%. In areas with clusters of eosinophils, up to 50% of the eosinophils were seen to generate eosinophil extracellular traps., Conclusion: Eosinophil extracellular traps are seen in both infectious and noninfectious inflammatory skin diseases and are particularly common in Wells syndrome., (Copyright © 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Because of advances in our understanding of the hypereosinophilic syndrome (HES) and the availability of novel therapeutic agents, the original criteria defining these disorders are becoming increasingly problematic. Here, we discuss shortcomings with the current definition of HES and recent developments in the classification of these disorders. Despite significant progress in our understanding of the pathogenesis of some forms of HES, the current state of knowledge is still insufficient to formulate a new comprehensive etiologic definition of HESs. Nevertheless, we suggest a new working definition that overcomes some of the most obvious limitations with the original definition.

Background: Hypereosinophilic syndrome (HES) is a heterogeneous group of rare disorders defined by persistent blood eosinophilia > or =1.5 x 10(9)/L, absence of a secondary cause, and evidence of eosinophil-associated pathology. With the exception of a recent multicenter trial of mepolizumab (anti-IL-5 mAb), published therapeutic experience has been restricted to case reports and small case series., Objective: The purpose of the study was to collect and summarize baseline demographic, clinical, and laboratory characteristics in a large, diverse cohort of patients with HES and to review responses to treatment with conventional and novel therapies., Methods: Clinical and laboratory data from 188 patients with HES, seen between January 2001 and December 2006 at 11 institutions in the United States and Europe, were collected retrospectively by chart review., Results: Eighteen of 161 patients (11%) tested were Fip1-like 1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRA) mutation-positive, and 29 of 168 patients tested (17%) had a demonstrable aberrant or clonal T-cell population. Corticosteroid monotherapy induced complete or partial responses at 1 month in 85% (120/141) of patients with most remaining on maintenance doses (median, 10 mg prednisone equivalent daily for 2 months to 20 years). Hydroxyurea and IFN-alpha (used in 64 and 46 patients, respectively) were also effective, but their use was limited by toxicity. Imatinib (used in 68 patients) was more effective in patients with the FIP1L1-PDGFRA mutation (88%) than in those without (23%; P < .001)., Conclusion: This study, the largest clinical analysis of patients with HES to date, not only provides useful information for clinicians but also should stimulate prospective trials to optimize treatment of HES.

Background: Eosinophil differentiation, activation, and survival are largely regulated by IL-5. IL-5-mediated transmembrane signal transduction involves both Lyn-mitogen-activated protein kinases and Janus kinase 2-signal transducer and activator of transcription pathways., Objective: We sought to determine whether additional signaling molecules/pathways are critically involved in IL-5-mediated eosinophil survival., Methods: Eosinophil survival and apoptosis were measured in the presence and absence of IL-5 and defined pharmacologic inhibitors in vitro. The specific role of the serine/threonine kinase proviral integration site for Moloney murine leukemia virus (Pim) 1 was tested by using HIV-transactivator of transcription fusion proteins containing wild-type Pim-1 or a dominant-negative form of Pim-1. The expression of Pim-1 in eosinophils was analyzed by means of immunoblotting and immunofluorescence., Results: Although pharmacologic inhibition of phosphatidylinositol-3 kinase (PI3K) by LY294002, wortmannin, or the selective PI3K p110delta isoform inhibitor IC87114 was successful in each case, only LY294002 blocked increased IL-5-mediated eosinophil survival. This suggested that LY294002 inhibited another kinase that is critically involved in this process in addition to PI3K. Indeed, Pim-1 was rapidly and strongly expressed in eosinophils after IL-5 stimulation in vitro and readily detected in eosinophils under inflammatory conditions in vivo. Moreover, by using specific protein transfer, we identified Pim-1 as a critical element in IL-5-mediated antiapoptotic signaling in eosinophils., Conclusions: Pim-1, but not PI3K, plays a major role in IL-5-mediated antiapoptotic signaling in eosinophils.

Background: Atopic eczema (AE) is a chronic inflammatory skin disorder characterized by eczematous skin lesions, pruritus, and typical histopathologic features., Objective: We asked whether depletion of B cells by monoclonal anti-CD20 antibody therapy (rituximab) would improve severe AE., Methods: Six patients (4 women and 2 men) with severe AE received 2 intravenous applications of rituximab, each 1000 mg, 2 weeks apart. To evaluate the efficacy of rituximab, we monitored clinical parameters (eczema area and severity index, pruritus), total and allergen-specific IgE levels, skin histology, and inflammatory cells and cytokine expression in the skin and peripheral blood before and after therapy., Results: All patients showed an improvement of their skin symptoms within 4 to 8 weeks. The eczema area and severity index significantly decreased (before therapy, 29.4 +/- 4.3; week 8, 8.4 +/- 3.6; P < .001). Histologic alterations such as spongiosis, acanthosis, and dermal infiltrate, including T and B cell numbers, also dramatically improved. However, whereas blood B cells were below detectable levels as a consequence of rituximab administration, skin B cells were reduced by approximately 50% only. Expression of IL-5 and IL-13 was reduced after therapy. Moreover, whereas allergen-specific IgE levels were not altered, we observed a slight reduction in total IgE concentrations in blood., Conclusions: B cells play a major role in AE pathogenesis. Treatment with an anti-CD20 antibody leads to an impressive improvement of AE in patients with severe disease.

Eosinophilic inflammatory responses occur in association with multiple disorders. Although the initial cause and the affected organs vary among the different eosinophilic disorders, there are only 2 major pathways that mediate eosinophilia: (1) cytokine-mediated increased differentiation and survival of eosinophils (extrinsic eosinophilic disorders), and (2) mutation-mediated clonal expansion of eosinophils (intrinsic eosinophilic disorders). Independent from the original trigger, the most common cause of eosinophilia is the increased generation of IL-5-producing T cells. In some cases, tumor cells are the source of eosinophil hematopoietins. The intrinsic eosinophilic disorders are characterized by mutations in pluripotent or multipotent hematopoietic stem cells leading to chronic myeloid leukemias with eosinophils as part of the clone. Here, we propose a new classification of eosinophilic disorders on the basis of these obvious pathogenic differences between the 2 groups of patients. We then discuss many known eosinophilic disorders, which can be further subdivided by differences in T-cell activation mechanisms, origin of the cytokine-producing tumor cell, or potency of the mutated stem cell. Interestingly, many subgroups of patients originally thought to have the idiopathic hypereosinophilic syndrome can be integrated in this classification.

Background: Human intravenous immunoglobulin (IVIg) preparations are used for the treatment of autoimmune and allergic diseases. Natural autoantibodies are believed to contribute to IVIg-mediated anti-inflammatory effects., Objective: To address the question of whether IVIg preparations contain anti-sialic acid-binding Ig-like lectin-8 (anti-Siglec-8) autoantibodies., Methods: The presence of possible anti-Siglec-8 autoantibodies in IVIg preparations was first examined by functional eosinophil death and apoptosis assays. Specificity of IVIg effects was shown by depleting anti-Siglec-8 autoantibodies from IVIg. Binding of purified anti-Siglec-8 autoantibodies to recombinant Siglec-8 was demonstrated by an immunodot assay., Results: IVIg exerts cytotoxic effects on purified human blood eosinophils. Both potency and efficacy of the IVIg-mediated eosinophil killing effect was enhanced by IL-5, granulocyte/macrophage colony-stimulating factor, IFN-gamma, TNF-alpha, and leptin. Similarly, inflammatory eosinophils obtained from patients suffering from the hypereosinophilic syndrome (HES) demonstrated increased Siglec-8 cytotoxic responses when compared with normal blood eosinophils. Pharmacologic blocking experiments indicated that the IVIg-mediated additional eosinophil death in the presence of cytokines is largely caspase-independent, but it depends on reactive oxygen species. Anti-Siglec-8 autoantibody-depleted IVIg failed to induce caspase-independent eosinophil death., Conclusion: IVIg preparations contain natural anti-Siglec-8 autoantibodies., Clinical Implications: Anti-Siglec-8 autoantibodies present in IVIg preparations may have therapeutic relevance in autoimmune and allergic diseases, respectively, such as Churg-Strauss syndrome.

Hypereosinophilic syndromes are a heterogeneous group of uncommon disorders characterized by the presence of marked peripheral blood eosinophilia, tissue eosinophilia, or both, resulting in a wide variety of clinical manifestations. Although corticosteroids are the first-line therapy for many of these disorders, approaches to the treatment of patients who do not tolerate or are unresponsive to corticosteroids are poorly standardized. A multidisciplinary group of 37 clinicians and scientists participated in a workshop held in May 2005 in Bern, Switzerland to discuss current and future approaches to therapy for 3 eosinophil-mediated disorders: hypereosinophilic syndrome, Churg-Strauss syndrome, and eosinophil-associated gastrointestinal disease. The goal of the workshop was to summarize available data regarding treatment of these disorders to identify the most promising therapies and approaches for further study. There was consensus among all of the participants that the identification of markers of disease progression to assess treatment responses is a research priority for all 3 disorders. Furthermore, the need for newer therapeutic strategies and novel drugs, as well as multicenter trials to assess all treatment modalities, was emphasized.

Background: Leptin regulates food intake, as well as metabolic, endocrine, and immune functions. It exerts proliferative and antiapoptotic activities in a variety of cell types, including T cells. Leptin also stimulates macrophages and neutrophils, and its production is increased during inflammation., Objective: We sought to examine the expression of leptin receptors on eosinophils and the effect of recombinant leptin on proapoptotic pathways in these cells., Methods: The presence of leptin receptor was examined by means of RT-PCR and immunofluorescence analysis in freshly isolated blood eosinophils and tissue eosinophils. The effect of recombinant leptin on apoptotic pathways in eosinophils was studied by using flow cytometric, immunoblotting, and immunofluorescence techniques., Results: Human eosinophils express leptin surface receptors under in vitro and in vivo conditions, and leptin delays apoptosis of mature eosinophils in vitro. The antiapoptotic effects of leptin were concentration dependent and blocked by an anti-leptin receptor mAb. The efficacy of leptin to block eosinophil apoptosis was similar to that of GM-CSF. Leptin delayed the cleavage of Bax, as well as the mitochondrial release of cytochrome c and second mitochondria-derived activator of caspase, suggesting that it blocks proapoptotic pathways proximal to mitochondria in eosinophils. Using pharmacological inhibitors, we obtained evidence that leptin initiates a signaling cascade involving phosphatidylinositol-3-OH kinase and mitogen-activated protein kinase-dependent pathways in eosinophils., Conclusion: Leptin is a survival cytokine for human eosinophils, a finding with potential pathologic relevance in allergic and parasitic diseases.

Background: In several clinical studies, topical calcineurin inhibitors have been shown to be effective in the treatment of atopic dermatitis (AD). They target signaling pathways that control gene expression, particularly the expression of cytokines., Objective: We examined the cellular infiltrate in skin lesions of 10 patients with AD and characterized the cytokine pattern expressed by the infiltrating cells before and after short-term topical therapy with tacrolimus 1% ointment., Methods: Skin biopsies were examined for histologic alterations (hematoxylin and eosin staining), composition of the cellular inflammatory infiltrate (immunofluorescence), and cytokine expression (ribonuclease protection assay, ELISA, immunofluorescence) before as well as 1 and 3 weeks after initiation of tacrolimus therapy. For comparison, biopsies from nonlesional AD and normal skin were analyzed. Systemic immunologic effects were assessed by analyzing peripheral blood leukocytes (immunofluorescence) as well as in vitro stimulated pan-T-cell cytokine production (ELISA)., Results: All patients showed a significant improvement of their skin lesions associated with a marked regression of spongiosis, acanthosis, and density of the cellular infiltrate in the dermis. The last was a result of reduced infiltration of T cells, B cells, and eosinophils. In contrast, the numbers of mast cells did not change. Moreover, the expression of the T H 2 cytokines IL-5, IL-10, and IL-13 in CD4 + T cells was reduced after therapy. Interestingly, tacrolimus therapy was also associated with a reduction of CD8 + T cells expressing the T H 1 cytokine IFN-gamma. Furthermore, the numbers of epidermal CD1a + dendritic cells increased after treatment. In the peripheral blood, a decrease of granulocytes (eosinophils and neutrophils) but no changes in the distribution of lymphocyte subpopulations were noticed., Conclusion: Topical tacrolimus treatment has anti-inflammatory effects on AD skin as indicated by reduced infiltration of cytokine expressing inflammatory cells. No evidence for drug-induced systemic immunosuppression was obtained.

Background: Although there have been several reports suggesting the presence of physiologic anti-CD95 (Fas, APO-1) autoantibodies in human intravenous Ig (IVIg) preparations, it is still unclear whether and under which conditions these autoantibodies block or stimulate the CD95 receptor., Objective: We examined the effects of IVIg on CD95-mediated apoptosis in CD95-sensitive human blood neutrophils in vitro., Methods: The presence of anti-CD95 antibodies was determined by competition assays with flow cytometry. Cell death and apoptosis were assessed by ethidium bromide uptake test and annexin V staining, respectively., Results: Pretreatment of neutrophils with IVIg prevented binding of FITC-conjugated anti-CD95 mAb to the cell surface, suggesting that IVIg contains CD95 autoantibodies. By using low concentrations of IVIg (1 to 10 mg/mL), we observed a dose-dependent inhibition of anti-CD95 mAb (CH11)-mediated neutrophil apoptosis. Higher concentrations of IVIg (20 to 50 mg/mL), however, induced neutrophil death and apoptosis in a dose-dependent manner. This effect was partially blocked by soluble CD95 receptors (recombinant Fc-Fas) but not by an anti-CD95 blocking mAb, which was shown to recognize the CH11 epitope of CD95., Conclusion: Both agonistic and antagonistic anti-CD95 antibodies are present in IVIg, and the effect on CD95 is dose-dependent. Our findings have potential implications for IVIg treatment, which is intended to target the CD95 receptor.

The idiopathic hypereosinophilic syndrome is associated with expansion of an IL-5-producing T-cell subset in a subgroup of patients. Identification of such patients is critical to adequate management because there is some evidence that they present an increased risk for development of T-cell lymphoma. Although the T(H)2-like cells often bear an aberrant surface phenotype and can readily be detected with flow cytometry, we now show that lymphocyte phenotyping might be normal in some cases. In contrast, serum thymus and activation-regulated chemokine levels are consistently increased in such patients compared with others with persistent idiopathic hyper-eosinophilia and could therefore represent a useful diagnostic tool.

Background: Idiopathic eosinophilic esophagitis (IEE) is a chronic-inflammatory disorder of the esophagus of unknown origin. The established cornerstone of diagnosis is a dense infiltration of the esophagus with eosinophils, but neither the precise pattern of inflammatory cell infiltration nor the mechanisms that likely contribute to induction and maintenance of the inflammatory response have been described., Objective: The intention of this study was to characterize the esophageal inflammatory infiltrate and the expression of cytokines in the esophagus in this disease. In addition, we searched for immunologic abnormalities of blood leukocytes to exclude major primary hyporeactive and hyperreactive conditions of the immune system., Methods: Infiltration of inflammatory cells in the esophagus, stomach, and duodenum was analyzed by immunohistochemistry through use of mAbs against lineage-associated molecules. Cytokine expression was measured by ELISA and immunohistochemical analysis. Lymphocyte subpopulations in blood were determined by means of flow cytometry., Results: High eosinophil infiltration into the esophageal squamous epithelium was observed in patients with IEE but not in control subjects. Interestingly, increased T-cell and mast cell numbers were also found within the epithelium in these patients. In contrast, the numbers of inflammatory cells were not increased in the stomach and duodenum in patients with IEE, suggesting a specific inflammatory process within the esophagus. Moreover, increased expression of IL-5 and TNF-alpha was observed in esophageal epithelial biopsy specimens. The distribution of lymphocyte subsets in the peripheral blood and their capacity to generate cytokines did not reflect the changes observed at the inflammatory site., Conclusions: IEE is a selective inflammatory response of the esophagus. T cells, IL-5, eosinophils, and IgE-mediated mechanisms appear to be involved, giving rise to the possibility that allergic reactions might play a role in the pathogenesis of the disease.

Background: CD137 (ILA/4-1BB), a member of the TNF/nerve growth factor receptor superfamily, has previously been suggested to be involved in T-cell activation and differentiation., Objective: The aim of this study was to investigate expression and potential function of CD137 in eosinophils., Methods: Eosinophils were isolated from normal control subjects as well as from patients with bronchial asthma, patients with atopic dermatitis, and patients with idiopathic eosinophilia. CD137 expression was analyzed by RT-PCR and flow cytometry. The in situ expression of CD137 on eosinophils in nasal polyp and skin tissues was analyzed through use of immunohistochemistry. To examine whether CD137 regulates eosinophil death and apoptosis, cells were stimulated with a plate-bound anti-CD137 antibody in the presence or absence of survival cytokines. Cell death was measured by means of an ethidium bromide exclusion test. Apoptosis was determined by analyzing phosphatidylserine surface exposure., Results: Blood and tissue eosinophils from patients with IgE-mediated allergic responses (atopic dermatitis, extrinsic asthma) express CD137. In contrast, eosinophils from normal control individuals and patients with non-IgE-mediated eosinophilic inflammatory responses (intrinsic asthma, idiopathic eosinophilia) express neither detectable levels of mRNA nor protein for CD137. Expression of CD137 in eosinophils was induced in vitro by stimulating the cells with supernatants derived from in vivo- or in vitro-activated T cells, suggesting that a soluble T cell-derived factor might be responsible for the observed phenomenon. Although CD137 expression was associated with increased IgE levels, IL-4 and IL-13 did not induce CD137 gene expression in eosinophils. Activation of CD137 abrogated both GM-CSF-mediated and IL-5-mediated antiapoptosis in CD137-expressing eosinophils but not in CD137-deficient eosinophils. In contrast, the survival effect of IFN-gamma was not affected by anti-CD137 treatment., Conclusion: Our data indicate that CD137 activation might limit GM-CSF-mediated and IL-5-mediated antiapoptosis of eosinophils. The absence of this potential anti-inflammatory mechanism might further increase eosinophil numbers at inflammatory sites in patients with intrinsic asthma and patients with idiopathic eosinophilia. The T cell-derived factor that induces CD137 expression in eosinophils remains to be identified.