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Eosinophils are granule-containing leukocytes which develop in the bone marrow. For many years, eosinophils have been recognized as cytotoxic effector cells, but recent studies suggest that they perform additional immunomodulatory and homeostatic functions. Autophagy is a conserved intracellular process which preserves cellular homeostasis. Autophagy defects have been linked to the pathogenesis of many human disorders. Evidence for abnormal regulation of autophagy, including decreased or increased expression of autophagy-related (ATG) proteins, has been reported in several eosinophilic inflammatory disorders, such as Crohn's disease, bronchial asthma, eosinophilic esophagitis, and chronic rhinosinusitis. Despite the increasing extent of research using preclinical models of immune cell-specific autophagy deficiency, the physiological relevance of autophagic pathway in eosinophils has remained unknown until recently. Owing to the increasing evidence that eosinophils play a role in keeping organismal homeostasis, the regulation of eosinophil functions is of considerable interest. Here, we discuss the most recent advances on the role of autophagy in eosinophils, placing particular emphasis on insights obtained in mouse models of infections and malignant diseases in which autophagy has genetically dismantled in the eosinophil lineage. These studies pointed to the possibility that autophagy-deficient eosinophils exaggerate inflammation. Therefore, the pharmacological modulation of the autophagic pathway in these cells could be used for therapeutic interventions.

Benralizumab: Targeting the IL-5 Receptor in Severe Eosinophilic Asthma Abstract. For patients with difficult-to-control, severe bronchial asthma, highly effective, targeted treatment options are available in addition to inhaled medication. In the presence of eosinophilia, inhibition of the interleukin-5 (IL‑5) axis with specific monoclonal antibodies promises to be an effective alternative to continuous systemic steroid therapy with few side effects. This review summarizes the data on benralizumab, a specific antibody against the IL-5 receptor alpha preventing receptor stimulation by IL-5 and activating a NK-cell mediated cytotoxic reaction with apoptosis of eosinophils. The s.c.-application of benralizumab leads within days to a virtually complete depletion of blood eosinophils with consecutive improvement in lung function and stabilization of asthma. For selected severe asthmatics, this is a promising therapy option.

Benralizumab: Targeting the IL-5 Receptor in Severe Eosinophilic Asthma Abstract. Abstract:For patients with difficult-to-control, severe bronchial asthma, highly effective, targeted treatment options are available in addition to inhaled medication. In the presence of eosinophilia, inhibition of the interleukin-5 (IL-5) axis with specific monoclonal antibodies promises to be an effective alternative to continuous systemic steroid therapy with few side effects. This review summarizes the data on benralizumab, a specific antibody against the IL-5 receptor alpha preventing receptor stimulation by IL-5 and activating a NK-cell mediated cytotoxic reaction with apoptosis of eosinophils. The s.c.-application of benralizumab leads within days to a virtually complete depletion of blood eosinophils with consecutive improvement in lung function and stabilization of asthma. For selected severe asthmatics, this is a promising therapy option.

Asthma is a widespread chronic inflammatory disease, which has a highly heterogeneous etiopathogenesis, with predominance of either T‑helper cell type 2 (Th2; type 2) or non-Th2 (non-type 2) mechanisms. Together with cardiovascular or autoimmune diseases, obesity, and others, asthma belongs to so called noncommunicable diseases, a group of disorders with immunometabolic links as underlying mechanisms. So far, obesity and asthma have been considered mostly independently, but there are clear signs of relevant interactions. First, obese patients are at increased risk of asthma or asthma‑like symptoms. Second, asthma accompanied by obesity is more severe and more difficult to treat. A specific phenotype called obesity‑associated asthma has been also described, which is late‑onset, rather severe, non-type 2‑driven disease, present mostly in women. In addition, obesity can coincide with asthma also in children, and, although obesity generally skews the Th1/Th2 balance towards Th1, it can also accompany type 2‑driven asthma. However, those combinations represent less precisely defined disease entities. Despite a substantial increase in our knowledge on the mechanisms mediating the effects of obesity on the development of asthma in several recent years, still much needs to be done, especially on the molecular level.

The asthmatic airways are highly susceptible to inflammatory injury by air pollutants such as ozone (O 3 ), characterized by enhanced activation of eosinophilic granulocytes and a failure of immune protective mechanisms. Eosinophil activation during asthma exacerbation contributes to the proinflammatory oxidative stress by high levels of nitric oxide (NO) production and extracellular DNA release. Surfactant protein-D (SP-D), an epithelial cell product of the airways, is a critical immune regulatory molecule with a multimeric structure susceptible to oxidative modifications. Using recombinant proteins and confocal imaging, we demonstrate here that SP-D directly bound to the membrane and inhibited extracellular DNA trap formation by human and murine eosinophils in a concentration and carbohydrate-dependent manner. Combined allergic airway sensitization and O 3 exposure heightened eosinophilia and nos2 mRNA (iNOS) activation in the lung tissue and S-nitrosylation related de-oligomerisation of SP-D in the airways. In vitro reproduction of the iNOS action led to similar effects on SP-D. Importantly, S-nitrosylation abolished the ability of SP-D to block extracellular DNA trap formation. Thus, the homeostatic negative regulatory feedback between SP-D and eosinophils is destroyed by the NO-rich oxidative lung tissue environment in asthma exacerbations., (©2018 Society for Leukocyte Biology.)

Based on a case report an overview on the differential diagnostic considerations with respect to blood hypereosinophilia (HE) and hypereosinophilic syndromes (HES) in childhood is given. A 13-year-old boy was admitted for the clarification of an asthma. In the blood count an increased HE with 3 500/µl (30%) was found along with elevated total serum IgE and IL-5 level (2 000 IU/ml and 17 pg/ml). Lung function showed an obstruction (FEV1 38%). Radiologically the picture of bronchiectasis and mucus pluggine appeared. In the BAL a HE (76%) with raised IL-5 level was apparent. Histologically asthma was diagnosed with mucostasis, hypertrophy of the bronchial wall musculature and a lung HE. Differential-diagnostically an ABPA, a Churg-Strauss-Syndrome, a parasitosis, drug associated HE, allergies and malignant disease could be excluded. An aberrant T-cell clone in peripheral blood was detected by flow cytometry and T-cell receptor clonal rearrangements by PCR, leading to the diagnosis of a lymphoid variant of HES (L-HES). Failure to detect the FIP1L1-PDGFRA gene fusion and a normal bone marrow examination could exclude a neoplastic HES (HESN). After steroid initiation, prompt decrease of blood eosinophilia with resolution of symptoms was observed. Steroid discontinuation led to eosinophilia recurrence associated with disease symptoms. As steroid-sparing agent the immunosuppressive azathioprine was additionally given; steroid doses could be decreased and stopped in the course. This case demonstrated the range of HE evaluation in infancy. With asthma one should also consider the possibility of a L-HES., (© Georg Thieme Verlag KG Stuttgart · New York.)

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.)

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.)

Asthma is a chronic inflammatory disease of the airways. The treatment of asthma is far from optimal and hence the need for novel therapeutic agents exists. The purpose of this study was to assess the anti-asthma effects of an enaminone, E121, and also its effects on human peripheral blood mononuclear cell proliferation and cytokine release. The effects of E121 were assessed in an ovalbumin-induced model of airway inflammation and airway hyperresponsiveness. In addition, the effects of E121 on phytohemagglutinin (PHA), anti-CD3 monoclonal antibody and lipopolysaccharide (LPS)-induced human peripheral blood mononuclear cell proliferation and cytokine release, respectively, were assessed. Treatment of mice with E121 significantly decreased the ovalbumin-induced increase in airway total cell influx and eosinophil infiltration and this was associated with an inhibition of ovalbumin-induced airway hyperresponsiveness. Moreover, E121 reduced PHA and anti-CD3-induced human peripheral blood mononuclear cell proliferation in vitro. E121 also inhibited PHA, anti-CD3 monoclonal antibody and LPS-induced cytokine release from human peripheral blood mononuclear cell cultures. These findings indicate that E121 exhibits anti-inflammatory and immunosuppressive activities., (2009 Elsevier B.V. All rights reserved.)

Cytokines play a critical role in the pathogenesis of asthma. Asthma resolution may depend on the correction of dysregulated cytokine expression, which is a characteristic feature of this chronic inflammatory disease. It is, therefore, not surprising that attempts have been made to either block cytokines present at elevated levels or to substitute cytokines that are insufficiently expressed in asthma. In this article, the results of these studies are discussed, and the obtained insights regarding asthma pathogenesis and new treatment options are summarized.

Background: Interferon (IFN)-alpha is a cytokine that possesses potent anti-viral and immunoregulatory activities. We aimed to assess clinical and immunological effects of low-dose IFN-alpha in patients with severe corticosteroid-resistant asthma with and without Churg-Strauss syndrome. There is currently no efficient pharmacological treatment available for this group of patients., Methods: We studied 10 patients with corticosteroid-resistant asthma, in which 3x10(6) IU/day IFN-alpha were administrated in addition to the prednisone dose given already before introduction of the cytokine therapy. The prednisone dose was gradually reduced dependent on the clinical situation and used as a clinical readout to evaluate the efficacy of the cytokine therapy. To distinguish between IFN-alpha- and prednisone-mediated immunological changes, the corticosteroid dose was kept constant for at least 2 weeks upon introduction of the cytokine therapy in seven patients. The effects of treatment on clinical and immunological parameters were measured at 2-4 weeks and 5-10 months depending on the availability of the patient., Results: Interferon-alpha treatment rapidly improved the clinical situation as assessed by lung function parameters and required prednisone dose. Important immunological changes included: decreased leukocyte numbers, increased relative numbers of CD4+ T cells, increased differentiation of T helper (Th)1 cells, and increased expression of interleukin (IL)-10 in peripheral blood mononuclear cells., Conclusion: Interferon-alpha treatment was associated with dramatic improvements in the condition of patients with corticosteroid-resistant asthma with and without Churg-Strauss syndrome. Potential mechanisms of action include the establishment of a correct Th1/Th2 balance and the induction of the anti-inflammatory IL-10 gene.

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.

The effect of systemic glucocorticoid therapy on immune parameters was studied in patients with bronchial asthma. Patients were divided into two groups: 1) those receiving oral glucocorticoid; 2) control patients who did not receive systemic glucocorticoid treatment. The glucocorticoid dose varied between 5 and 70 mg per day. Patients had been taking oral therapy for at least 1 year. Glucocorticoid treatment was associated with an increased frequency of respiratory tract infections. Therefore, we need to define immune parameters which may predict an increased risk of infections. In this study, we analyzed several surface markers on lymphocytes and monocytes by flow cytometry. A significant reduction of the ratio of peripheral blood CD4+ to CD8+ T cells was associated with the administration of oral glucocorticoids. Furthermore, the expression of the HLA-DR molecule on monocytes was reduced in patients with systemic glucocorticoid therapy compared to control patients. Moreover, the capacity to elaborate cytokines by peripheral blood mononuclear cells upon stimulation was greatly reduced after exposure to glucocorticoids in vivo and in vitro. In addition, the humoral immune response was affected, because reduced IgG, IgM, and IgA levels were observed in patients receiving oral glucocorticoids. These results indicate that systemic glucocorticoid treatment in patients with bronchial asthma is associated with cellular and humoral immunosuppression which results in an increased risk of bacterial and viral infections.

P-Glycoprotein is a transmembrane efflux pump for different lipophilic drugs including glucocorticosteroids. Thus, upregulation of P-glycoprotein may provide a mechanism for reduced glucocorticosteroid responses as they occur in steroid-resistant asthma. To address this issue, we have examined freshly isolated peripheral blood mononuclear cells and granulocytes with regards to P-glycoprotein functional and surface expression. Using two-color immuno fluorescence techniques, we demonstrated a direct correlation between the efflux of the fluorescent dye Rh 123 and P-glycoprotein surface expression in lymphocytes, NK (natural killer) cells, monocytes and granulocytes. P-Glycoprotein levels varied widely between different leucocytes, with NK cells and CD8+ T cells having high, and granulocytes having no detectable levels. There was no evidence for upregulation of P-glycoprotein expression in any cell type from patients with steroid-resistant asthma compared to patients with steroid-sensitive or mild asthma. These results suggest that increased P-glycoprotein expression can be excluded as a mechanism for steroid resistance. Interestingly, a down regulation of P-glycoprotein expression in B cells was associated with systemic glucocorticosteroid treatment in vivo and in vitro. Whether this phenomenon may account for reduced immunoglobulin levels associated with oral glucocortico-steroid therapy remains to be determined.

Eosinophils possess the capacity to synthesize various cytokines. We demonstrate that IL-8 mRNA and protein are constitutively expressed by freshly isolated resting human eosinophils. Most of the patients with bronchial asthma or atopic dermatitis show evidence for up-regulated IL-8 protein expression in eosinophils but not in neutrophils, suggesting that an eosinophil-specific cytokine may act in these patients. To investigate whether the intracellular IL-8 can be released, eosinophils were stimulated by different cytokines and platelet-activating factor. Priming with granulocyte-macrophage CSF and a subsequent 25-min stimulation with RANTES or platelet-activating factor resulted in release of IL-8 from highly purified human eosinophils in vitro. As the eosinophil is the predominant cell in asthmatic inflammation, we determined IL-8 concentrations in bronchoalveolar lavage fluids from normal individuals and asthmatic patients. Bronchoalveolar lavage fluids from patients with bronchial asthma consistently demonstrated high IL-8 concentration compared with the controls. This suggests that IL-8 is released in vivo by inflammatory bronchial cells in asthma.

Platelet-activating factor (PAF) may play a role in the regulation of immune responsiveness and is a potent mediator in asthmatic inflammation. However, as yet, the mechanisms whereby PAF mediates its pleiomorphic effects on immune cells have not been elucidated. Because PAF is a potent chemotactic factor for eosinophils, the presence of receptors for PAF (PAFR) on lymphocytes may provide a mechanism for the concurrent recruitment of both eosinophils and T lymphocytes into the airways of asthmatic patients. To address this issue, we have examined freshly isolated PBMC and granulocytic cells as well as various T and B lymphocyte lines with regards to PAFR expression and PAF-induced changes in intracellular calcium concentration. Using two-color immunofluorescence techniques and highly purified cell populations, it was not possible to detect surface PAFR protein or functional PAFR on resting and in vivo or in vitro activated T and B cells derived from nonallergic individuals or patients with allergic asthma. In addition, we were unable to detect PAFR mRNA, protein, or functional response to PAF in human or murine T cell lines. In contrast, we found functional PAFR in most B lymphoblastoid cell lines. Within the PBMC population, CD14+ cells respond to PAF. These results suggest that PAF does not interact directly with lymphocytes and thus that previous observations suggestive of such an interaction likely reflect the effects of PAF on monocytes. PAF-induced increases in intracellular calcium concentration were also detected in neutrophils and eosinophils, but were lower in granulocytes relative to the levels detected in monocytes.

Asthma is a multifactorial disease of unknown etiology but often associated with atopy and inflammation. Previous studies in adult asthma have demonstrated the presence of activated T cells in blood, bronchoalveolar lavage (BAL) fluid, and bronchial tissue, and the relevance of their soluble products for eosinophil function. In view of these observations, it was hypothesized that similar pathogenetic mechanisms also occur in childhood asthma. In fact, peripheral blood T lymphocytes in 14 children with house-dust mite allergic asthma showed clear evidence of T cell activation as measured by the expression of CD25 and HLA-DR antigen. Without changing medication, significant reduction of the IL-2 receptor alpha-chain expression within the CD4+ lymphocyte population was observed after only 3 weeks of allergen avoidance. Within this time period, absolute and relative eosinophil numbers decreased to normal levels. After 5 weeks in an area of low house-dust mite exposure, lung function also presented evidence for clinical improvement of the asthmatic disease. These results indicate similar pathogenetic mechanisms in childhood and adult asthma. Furthermore, they suggest that allergen avoidance may contribute to the efficient therapy of asthma in patients with house-dust mite IgE-meditated allergy.