Eosinophil granule proteins and their role in disease

Antimicrobial Activity of Human Eosinophil Granule Proteins

Eosinophils secrete a number of proinflammatory mediators that include cytokines, chemokines, and granule proteins which are responsible for the initiation and maintenance of inflammatory responses. The eosinophil granule proteins, ECP, EDN, MBP, and EPO, possess antimicrobial activity against bacteria, helminths, protozoa, and viruses. In this chapter, we describe various assays used to detect and quantitate the antimicrobial activities of eosinophil granule proteins, particularly ECP and EDN. We have taken a model organism for each assay and described the method for antiviral, antihelminthic, antiprotozoan, and antibacterial activity of purified eosinophil granule proteins.

Effect of E-Cigarette aerosol exposure on airway inflammation in a murine model of asthma

OBJECTIVE

The popularity of electronic cigarettes (E-Cigs) smoking is increasing worldwide including patients with asthma. In this study, the effects of E-Cigs aerosol exposure on airway inflammation in an allergen-driven murine model of asthma were investigated.

MATERIALS AND METHODS

Balb/c mice were randomly assigned to; control group (received fresh air, Ovalbumin (Ova) sensitization and saline challenge), E-Cig group (received E-Cig aerosol, Ova sensitization, and saline challenge), Ova S/C group (received fresh air, Ova sensitization and Ova challenge) and E-Cig + Ova S/C group. Bronchoalveolar lavage fluid (BALF) and lung tissue were evaluated for inflammatory cells and inflammatory mediators, respectively.

RESULTS

Exposure to E-Cig aerosol significantly increased the number of all types of inflammatory cells in BALF (p < 0.05). Further, E-Cig aerosol reduced levels of transforming growth factor (TGF)-β1 and matrix metalloproteinase (MMP)-2 in lung tissue homogenate (p < 0.05). Combined E-Cig aerosol and Ova S/C increased the airway recruitment of inflammatory cells, especially neutrophils, eosinophils, and lymphocytes (p < 0.05), increased the level of interleukin (IL)-13, and reduced the level of TGF-β1 (p < 0.05).

CONCLUSIONS

E-Cig aerosol exposure induced airway inflammation in both control mice and allergen-driven murine model of asthma. The inflammatory response induced by E-Cig was slightly higher in allergen-driven murine model of asthma than in healthy animals.

Pharmacogenetics of Pediatric Asthma: Current Perspectives

Asthma is a chronic respiratory disease that affects 339 million people worldwide and has a considerable impact on the pediatric population. Asthma symptoms can be controlled by pharmacological treatment. However, some patients do not respond to therapy and continue suffering from symptoms, which impair the quality of life of patients and limit their daily activity. Genetic variation has been shown to have a role in treatment response. The aim of this review is to update the main findings described in pharmacogenetic studies of pediatric asthma published from January 1, 2018 to December 31, 2019. During this period, the response to short-acting beta-agonists and inhaled corticosteroids in childhood asthma has been evaluated by eleven candidate-gene studies, one meta-analysis of a candidate gene, and six pharmacogenomic studies. The findings have allowed validating the association of genes previously related to asthma treatment response (ADRB2, GSDMB, FCER2, VEGFA, SPAT2SL, ASB3, and COL2A1), and identifying novel associations (PRKG1, DNAH5, IL1RL1, CRISPLD2, MMP9, APOBEC3B-APOBEC3C, EDDM3B, and BBS9). However, some results are not consistent across studies, highlighting the need to conduct larger studies in diverse populations with more homogeneous definitions of treatment response. Once stronger evidence was established, genetic variants will have the potential to be applied in clinical practice as biomarkers of treatment response enhancing asthma management and improving the quality of life of asthma patients.

Precision medicine in childhood asthma

PURPOSE OF REVIEW

Childhood asthma is a heterogeneous disease and many children have uncontrolled disease. Therefore an individualized approach is needed to improve asthma outcomes in children. Precision medicine using clinical characteristics, biomarkers, and the rapidly involving field of genomics and pharmacogenomics aims to achieve asthma control and reduce future risks with less side-effects in individual children with asthma.

RECENT FINDINGS

It is not yet possible to select treatment options on clinical characteristics. Novel monoclonal antibodies are efficacious in patients with severe, eosinophilic asthma. Reduced lung function growth and early decline is a prevalent finding in children with persistent asthma. Pharmacogenetic studies have identified children at risk for cortisol suppression when using inhaled corticosteroids.

SUMMARY

Clinical characteristics and simple biomarkers like eosinophils, IgE, and the fraction of exhaled nitric oxide may be used in clinical practice for a basic precision medicine approach, deciding which children will have the best chance to respond to inhaled corticosteroids and to the biologicals omalizumab and mepolizumab.Further application of pharmacogenomics and breathomics needs additional studies before they can be applied as tools for precision medicine in individual children with asthma.

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.

Mepolizumab for the treatment of eosinophilic granulomatosis with polyangiitis

INTRODUCTION

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterized by asthma, hypereosinophilia, and progressive multiorgan involvement. Although not fully elucidated, advancement in our understanding of the pathophysiology of EGPA has led to the development of multiple new treatment targets.

AREAS COVERED

Herein we review the epidemiology, clinical manifestations, pathophysiology, treatments, and ongoing research in the management of EGPA. The central role of Interleukin-5 (IL-5) in the development and maintenance of hypereosinophilia will be discussed. The value of mepolizumab, an anti-IL-5 monoclonal antibody, in the treatment of EGPA is reviewed in detail.

EXPERT OPINION

The available literature supports the use of mepolizumab for the induction and maintenance of remission of refractory, relapsing, or glucocorticoid-dependent EGPA with potentially greater benefit in those who are ANCA-positive or those with greater eosinophilia ( ≥ 150 cells/ μ L). Despite these positive results, relapses remain frequent, and the need for both short- and long-term glucocorticoid use remains common. More research is needed to address these needs and determine the precise role of mepolizumab.

Biomarkers related to bullous pemphigoid activity and outcome

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disease of the skin. Investigation of the BP-associated pathophysiological processes during the last decades showed that the generation of autoantibodies directed against the hemidesmosome proteins BP180 and BP230, a hallmark of the BP-associated autoimmune response, leads to the recruitment of inflammatory immune cells at the dermal-epidermal junction, and subsequently to the release of a large amount of inflammatory molecules involved in blister formation. Analysis in transversal and longitudinal studies of autoantibodies and inflammatory molecules production both at the time of diagnosis and under treatment was mainly performed within the serum but also in the blister fluid. Some autoimmune or inflammatory molecules expression was related to the presence of clinical signs, while others were mere bystanders. In this review, we focused on the autoimmune and inflammatory molecules that have been identified as potential biomarkers of BP development and outcome.

Integrative approach identifies corticosteroid response variant in diverse populations with asthma

BACKGROUND

Although inhaled corticosteroid (ICS) medication is considered the cornerstone treatment for patients with persistent asthma, few ICS pharmacogenomic studies have involved nonwhite populations.

OBJECTIVE

We sought to identify genetic predictors of ICS response in multiple population groups with asthma.

METHODS

The discovery group comprised African American participants from the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-Ethnicity (SAPPHIRE) who underwent 6 weeks of monitored ICS therapy (n = 244). A genome-wide scan was performed to identify single nucleotide polymorphism (SNP) variants jointly associated (ie, the combined effect of the SNP and SNP × ICS treatment interaction) with changes in asthma control. Top associations were validated by assessing the joint association with asthma exacerbations in 3 additional groups: African Americans (n = 803 and n = 563) and Latinos (n = 1461). RNA sequencing data from 408 asthmatic patients and 405 control subjects were used to examine whether genotype was associated with gene expression.

RESULTS

One variant, rs3827907, was significantly associated with ICS-mediated changes in asthma control in the discovery set (P = 7.79 × 10^-8) and was jointly associated with asthma exacerbations in 3 validation cohorts (P = .023, P = .029, and P = .041). RNA sequencing analysis found the rs3827907 C-allele to be associated with lower RNASE2 expression (P = 6.10 × 10^-4). RNASE2 encodes eosinophil-derived neurotoxin, and the rs3827907 C-allele appeared to particularly influence ICS treatment response in the presence of eosinophilic inflammation (ie, high pretreatment eosinophil-derived neurotoxin levels or blood eosinophil counts).

CONCLUSION

We identified a variant, rs3827907, that appears to influence response to ICS treatment in multiple population groups and likely mediates its effect through eosinophils.

Heightened Systemic Levels of Neutrophil and Eosinophil Granular Proteins in Pulmonary Tuberculosis and Reversal following Treatment

Granulocytes are activated during Mycobacterium tuberculosis infection and act as immune effector cells, and granulocyte responses are implicated in tuberculosis (TB) pathogenesis. Plasma levels of neutrophil and eosinophil granular proteins provide an indirect measure of degranulation. In this study, we wanted to examine the levels of neutrophil and eosinophil granular proteins in individuals with pulmonary tuberculosis (PTB) and to compare them with the levels in individuals with latent TB (LTB). Hence, we measured the plasma levels of myeloperoxidase (MPO), neutrophil elastase, proteinase 3, major basic protein (MBP), eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), and eosinophil peroxidase (EPX) in these individuals. Finally, we also measured the levels of all of these proteins in PTB individuals following antituberculosis treatment (ATT). Our data reveal that PTB individuals are characterized by significantly higher plasma levels of MPO, elastase, proteinase 3, as well as MBP and EDN in comparison to those in LTB individuals. Our data also reveal that ATT resulted in the reversal of all of these changes, indicating an association with TB disease. Finally, our data show that the systemic levels of MPO and proteinase 3 can significantly discriminate PTB from LTB individuals. Thus, our data suggest that neutrophil and eosinophil granular proteins could play a potential role in the innate immune response and, therefore, the pathogenesis of pulmonary TB.

Elevated Systemic Levels of Eosinophil, Neutrophil, and Mast Cell Granular Proteins in Strongyloides Stercoralis Infection that Diminish following Treatment

Infection with the helminth parasite Strongyloides stercoralis (Ss) is commonly clinically asymptomatic that is often accompanied by peripheral eosinophilia. Granulocytes are activated during helminth infection and can act as immune effector cells. Plasma levels of eosinophil and neutrophil granular proteins convey an indirect measure of granulocyte degranulation and are prominently augmented in numerous helminth-infected patients. In this study, we sought to examine the levels of eosinophil, neutrophil, and mast cell activation-associated granule proteins in asymptomatic Ss infection and to understand their kinetics following anthelmintic therapy. To this end, we measured the plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, neutrophil elastase, myeloperoxidase, neutrophil proteinase-3, mast cell tryptase, leukotriene C4, and mast cell carboxypeptidase-A3 in individuals with asymptomatic Ss infection or without Ss infection [uninfected (UN)]. We also estimated the levels of all of these analytes in infected individuals following definitive treatment of Ss infection. We demonstrated that those infected individuals have significantly enhanced plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, elastase, myeloperoxidase, mast cell tryptase, leukotriene C4, and carboxypeptidase-A3 compared to UN individuals. Following the treatment of Ss infection, each of these granulocyte-associated proteins drops significantly. Our data suggest that eosinophil, neutrophil, and mast cell activation may play a role in the response to Ss infection.

T-Helper Type 2 Cells Direct Antigen-Induced Eosinophilic Skin Inflammation in Mice

Eosinophilic inflammation in combination with immunoglobulin E (IgE) production is a characteristic feature of atopic dermatitis. Although activated T-helper type (Th) 2 cells play critical roles in the local accumulation and activation of eosinophils, whether they induce eosinophilic skin inflammation, independent of the IgE-mediated pathway has been unclear. To address the functional role of T cells in allergic skin diseases, we herein transferred Th1/Th2-differentiated or naive DO11.10 T cells into unprimed BALB/c mice. Ovalbumin-specific Th2 cells, as well as eosinophils, accumulated in the skin upon antigen challenge, despite the absence of antigen-specific IgE. Neither antigen-specific Th1 nor naive T cells induced eosinophil accumulation, although Th1 cells by themselves migrated into the skin. Interleukin (IL)-4, IL-5, and eotaxin were specifically produced in the skin of antigen-challenged, Th2 cell-transferred mice, whereas interferon (IFN)-γ and regulated on activation, normal T cell expressed and secreted (RANTES) were preferentially produced in Th1 cells-transferred mice. Production of monocyte chemoattractant protein (MCP)-1 and MCP-3 was enhanced by both Th1 and Th2 cells. The accumulation of eosinophils and Th2 cells in the skin was suppressed by both dexamethasone and FK506, indicating an essential role of Th2 cells in eosinophil recruitment. We conclude that Th2 cells can induce eosinophilic infiltration into the skin in the absence of antigen-specific IgE.

Cell Type-Specific Immunomodulation Induced by Helminthes: Effect on Metainflammation, Insulin Resistance and Type-2 Diabetes

Recent epidemiological studies have documented an inverse relationship between the decreasing prevalence of helminth infections and the increasing prevalence of metabolic diseases ("metabolic hygiene hypothesis"). Chronic inflammation leading to insulin resistance (IR) has now been identified as a major etiological factor for a variety of metabolic diseases other than obesity and Type-2 diabetes (metainflammation). One way by which helminth infections such as filariasis can modulate IR is by inducing a chronic, nonspecific, low-grade, immune suppression mediated by modified T-helper 2 (Th2) response (induction of both Th2 and regulatory T cells) which can in turn suppress the proinflammatory responses and promote insulin sensitivity (IS). This article provides evidence on how the cross talk between the innate and adaptive arms of the immune responses can modulate IR/sensitivity. The cross talk between innate (macrophages, dendritic cells, natural killer cells, natural killer T cells, myeloid derived suppressor cells, innate lymphoid cells, basophils, eosinophils, and neutrophils) and adaptive (helper T [CD4⁺] cells, cytotoxic T [CD8⁺] cells and B cells) immune cells forms two opposing circuits, one associated with IR and the other associated with IS under the conditions of metabolic syndrome and helminth-mediated immunomodulation, respectively.

Pathological manifestations in lymphatic filariasis correlate with lack of inhibitory properties of IgG4 antibodies on IgE-activated granulocytes

Helminth parasites are known to be efficient modulators of their host’s immune system. To guarantee their own survival, they induce alongside the classical Th2 a strong regulatory response with high levels of anti-inflammatory cytokines and elevated plasma levels of IgG4. This particular antibody was shown in different models to exhibit immunosuppressive properties. How IgG4 affects the etiopathology of lymphatic filariasis (LF) is however not well characterized. Here we investigate the impact of plasma and affinity-purified IgG/IgG4 fractions from endemic normals (EN) and LF infected pathology patients (CP), asymptomatic microfilaraemic (Mf+) and amicrofilaraemic (Mf-) individuals on IgE/IL3 activated granulocytes. The activation and degranulation states were investigated by monitoring the expression of CD63/HLADR and the release of granule contents (neutrophil elastase (NE), eosinophil cationic protein (ECP) and histamine) respectively by flow cytometry and ELISA. We could show that the activation of granulocytes was inhibited in the presence of plasma from EN and Mf+ individuals whereas those of Mf- and CP presented no effect. This inhibitory capacity was impaired upon depletion of IgG in Mf+ individuals but persisted in IgG-depleted plasma from EN, where it strongly correlated with the expression of IgA. In addition, IgA-depleted fractions failed to suppress granulocyte activation. Strikingly, affinity-purified IgG4 antibodies from EN, Mf+ and Mf- individuals bound granulocytes and inhibited activation and the release of ECP, NE and histamine. In contrast, IgG4 from CP could not bind granulocytes and presented no suppressive capacity. Reduction of both the affinity to, and the suppressive properties of anti-inflammatory IgG4 on granulocytes was reached only when FcγRI and II were blocked simultaneously. These data indicate that IgG4 antibodies from Mf+, Mf- and EN, in contrast to those of CP, natively exhibit FcγRI/II-dependent suppressive properties on granulocytes. Our findings suggest that quantitative and qualitative alterations in IgG4 molecules are associated with the different clinical phenotypes in LF endemic regions.

Lymphatic Filariasis, also known as elephantiasis, infects an estimated 39 million people in 73 tropical and sub-tropical countries. The most severe clinical manifestations of the disease include swelling of the scrotal area and lower limbs (hydrocele and lymphedema). It is well admitted that host immune reactivity plays a critical role in the pathogenesis of the disease. Previous investigations have linked the non-cytolytic antibody IgG4 to the hyporesponsive states in filarial infections. However, few data exist on how this antibody is involved in the pathogenesis of human filariasis. Here we investigated the role of this antibody in disease pathogenesis by comparing the effect of plasma, IgG and IgG4 fractions from the four clinical categories of individuals; chronic pathology individuals (CP), asymptomatic microfilaria positive (Mf+) and negative (Mf-) and uninfected endemic normal individuals (EN) on activated granulocytes. We could show that granulocyte activation was significantly inhibited in the presence of plasma from EN and Mf+ and that, affinity-purified IgG4 antibodies from EN, Mf+ and Mf- individuals inhibited granulocyte activation in a dose-dependent manner via the immune receptors FcγRI and FcγRII. Our data also reveal significant functional differences between IgG4 molecules from EN, Mf+, Mf- and CP.

Eosinophil Cationic Protein (ECP), a predictive marker of bullous pemphigoid severity and outcome

Bullous Pemphigoid (BP) is an inflammatory rare autoimmune bullous dermatosis, which outcome cannot be predicted through clinical investigations. Eosinophils are the main immune infiltrated cells in BP. However, the release of Major Basic Protein (MBP), Eosinophil Derived Neurotoxin (EDN), and Eosinophil Cationic Protein (ECP) upon eosinophil activation has still not been evaluated with respect to BP development. MBP, EDN and ECP were measured by ELISA in serum (n = 61) and blister fluid (n = 20) of patients with BP at baseline, and in serum after 2 months of treatment (n = 41). Eosinophil activation in BP patients was illustrated at baseline by significantly higher MBP, EDN and ECP serum concentrations as compared with control subjects (n = 20), but without distinction according to disease severity or outcome. EDN and ECP values were even higher in the blister fluids (P < 0.01 and P < 0.05, respectively), whereas MBP values were lower (P < 0.001). ECP serum concentration decreased after 60 days of treatment in BP patients with ongoing remission but not in patients who later relapsed (P < 0.05). A reduction of at least 12.8 ng/mL in ECP concentrations provided a positive predictive value for remission of 81%, showing that ECP serum variation could be a useful biomarker stratifying BP patients at risk of relapse.

Reductions in eosinophil biomarkers by benralizumab in patients with asthma

BACKGROUND

Eosinophilic inflammation is frequently associated with increased asthma severity. Benralizumab is a humanized, afucosylated, anti-interleukin-5Rα monoclonal antibody that selectively depletes eosinophils and basophils through enhanced antibody-dependent cell-mediated cytotoxicity.

OBJECTIVE

To study effects of benralizumab on eosinophil counts and activity following administration to asthma patients.

METHODS

Sera were collected from asthma patients enrolled in two clinical studies. Placebo or benralizumab was subcutaneously administered to patients in Phase I (100 or 200 mg, multiple doses; N = 14; NCT00659659) and Phase IIa (25, 100, or 200 mg every 4 weeks; N = 24; NCT00783289) studies. Sera were also collected from healthy volunteers (N = 20) for comparison. Blood eosinophils, IL-5, eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), eotaxin/chemokine (C-C motif) 11 (CCL11), eotaxin-2/CCL24, tumor necrosis factor (TNF), and interferon-γ (IFN-γ) were measured at baseline and post-treatment.

RESULTS

Increased EDN concentrations were observed in sera of patients from both studies relative to healthy volunteers (p < 0.05). At baseline, sera EDN concentrations correlated with blood eosinophil counts (rs = 0.5; p < 0.05). Benralizumab reduced blood eosinophil numbers and sera EDN and ECP relative to baseline (p < 0.05). No changes in TNF or IFN-γ were observed, while serum IL-5, eotaxin/CCL11, and eotaxin-2/CCL24 increased after benralizumab administration vs. placebo (p < 0.05).

CONCLUSIONS

In two independent studies, serum IL-5, EDN, and ECP were modulated following benralizumab. Eosinophil depletion after benralizumab also resulted in significant reductions in EDN and ECP concentrations, suggesting that cytotoxic granule proteins were not released after eosinophil reduction.

Infektionsimmunologie8

Im Laufe der Entwicklung der Lebewesen traten die Organismen gegeneinander in Konkurrenz und entdeckten andere Spezies als eigene Lebensgrundlage oder Nahrung. Bei höheren Lebewesen sehen wir dies als selbstverständlich an und teilen Sie in Fleisch- und Pflanzenfresser ein. Bei niederen Lebewesen bezeichnen wir dies jedoch als pathogene Eigenschaft oder als parasitäre Lebensweise, wenn wir ihnen als Nahrungsgrundlage dienen. Zur Abwehr der Krankheitserreger entwickelten alle höheren Lebewesen ein Immunsystem, um das Fortbestehen der Spezies zu garantieren. Je weiter sich die Lebewesen entwickelt haben, desto höher hat sich auch das Immunsystem in einer Coevolution in Konkurrenz zu den Erregern entwickelt. Da das Immunsystem in der Evolution zur Infektionsabwehr entstanden ist, leiten sich seine übrigen physiologischen und pathophysiologischen Mechanismen von denen der Infektionsabwehr ab. Die Tumorabwehr entspricht der Abwehr von Viren und die Allergie der Abwehr von „nicht vorhandenen Parasiten“. Damit ist die Infektionsimmunologie der zentrale Punkt der Immunologie. Während wirbellose Tiere nur eine angeborene Immunität besitzen, hat sich bei den Wirbeltieren zusätzlich die spezifische (adaptive) Immunität entwickelt. Die Komplexität des Immunsystems steht dabei mit der Lebensdauer der Organismen und der Rate an Nachkommen im Einklang, d. h., je länger die Lebensdauer und je geringer die Anzahl der Nachkommen, desto komplexer muss das Immunsystem aufgebaut sein, um das Überleben der Art zu gewährleisten. Somit haben sich im Laufe der Evolution die in den vorherigen Kapiteln beschriebenen Abwehrsysteme entwickelt, die für die Abwehr von Infektionen koordiniert zusammenarbeiten müssen. Wichtig ist dabei, dass das Immunsystem den richtigen Reaktionsweg einschlägt, der den Erreger spezifisch bekämpfen kann, da sonst die Immunreaktion ins Leere läuft und der Erreger sich trotzdem weitervermehrt und den Körper schädigt.

Eosinophils in vasculitis: characteristics and roles in pathogenesis

Eosinophils are multifunctional granular leukocytes that are implicated in the pathogenesis of a wide variety of disorders, including asthma, helminth infection, and rare hypereosinophilic syndromes. Although peripheral and tissue eosinophilia can be a feature of many types of small-vessel and medium-vessel vasculitis, the role of eosinophils has been best studied in eosinophilic granulomatosis with polyangiitis (EGPA), where eosinophils are a characteristic finding in all three clinical stages of the disorder. Whereas numerous studies have demonstrated an association between the presence of eosinophils and markers of eosinophil activation in the blood and tissues of patients with EGPA, the precise role of eosinophils in disease pathogenesis has been difficult to ascertain owing to the complexity of the disease process. In this regard, results of clinical trials using novel agents that specifically target eosinophils are providing the first direct evidence of a central role of eosinophils in EGPA. This Review focuses on the aspects of eosinophil biology most relevant to the pathogenesis of vasculitis and provides an update of current knowledge regarding the role of eosinophils in EGPA and other vasculitides.

Eosinophil peroxidase induces expression of cholinergic genes via cell surface neural interactions

Eosinophils localize to and release their granule proteins in close association with nerves in patients with asthma and rhinitis. These conditions are associated with increased neural function. In this study the effect of the individual granule proteins on cholinergic neurotransmitter expression was investigated. Eosinophil peroxidase (EPO) upregulated choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) gene expression. Fluorescently labeled EPO was seen to bind to the IMR-32 cell surface. Both Poly-L-Glutamate (PLG) and Heparinase-1 reversed the up-regulatory effect of EPO on ChAT and VAChT expression and prevented EPO adhesion to the cell surface. Poly-L-arginine (PLA) had no effect on expression of either gene, suggesting that charge is necessary but insufficient to alter gene expression. EPO induced its effects via the activation of NF-κB. MEK inhibition led to reversal of all up-regulatory effects of EPO. These data indicate a preferential role of EPO signaling via a specific surface receptor that leads to neural plasticity.

Surfactant protein SP-D modulates activity of immune cells: proteomic profiling of its interaction with eosinophilic cells

Surfactant protein D (SP-D), a C-type lectin, is known to protect against lung infection, allergy and inflammation. Its recombinant truncated form comprising homotrimeric neck and CRD region (rhSP-D) has been shown to bring down specific IgE levels, eosinophilia and restore Th2-Th1 homeostasis in murine models of lung hypersensitivity. SP-D knockout mice show intrinsic hypereosinophilia and airway hyper-responsiveness that can be alleviated by rhSP-D. The rhSP-D can bind activated eosinophils, inhibit chemotaxis and degranulation, and selectively induce oxidative burst and apoptosis in sensitized eosinophils. A global proteomics study of rhSP-D-treated eosinophilic cell line AML14.3D10 identified large-scale molecular changes associated with oxidative burst, cell stress and survival-related proteins potentially responsible for apoptosis induction. The data also suggested an involvement of RNA binding- and RNA splicing-related proteins. Thus, the proteomics approach yielded a catalog of differentially expressed proteins that may be protein signatures defining mechanisms of SP-D-mediated maintenance of homeostasis during allergy.

An experimental study of inner ear injury in an animal model of eosinophilic otitis media

Conclusion:

As the periods of intratympanic injection of ovalbumin (OVA) to the middle ear became longer, marked eosinophil infiltration in the perilymphatic space was observed. Moreover severe morphological damage of the organ of Corti was observed in the 28-day antigen-stimulation side. These results indicate that eosinophilic inflammation occurred in the inner ear and caused profound hearing loss.

Objective:

The purpose of the present study was to elucidate the inner ear damage in a new animal model of eosinophilic otitis media (EOM) which we recently constructed.

Methods:

We constructed the animal model of EOM by intraperitoneal and intratympanic injection of OVA. Infiltrating cells and the inner ear damage were examined by histological study.

Results:

In the inner ear, a few eosinophils were seen in the scala tympani of the organ of Corti and the dilation of capillaries of the stria vascularis was observed in the 7-day stimulation side. In the 14-day antigen stimulation side, some eosinophils and macrophages were seen in not only the scala tympani but also the scala vestibule. In the 28-day antigen-stimulation side, severe morphological damage of the organ of Corti and many eosinophils, red blood cells, and plasma cells infiltrating the perilymph were observed.

Antimicrobial activity of human eosinophil granule proteins

Eosinophils secrete a number of proinflammatory mediators, like cytokines, chemokines, and granule proteins which are responsible for the initiation and sustenance of inflammatory response caused by them. The eosinophil granule proteins, ECP, EDN, MBP, and EPO possess antimicrobial activity against bacteria, helminths, protozoa, and viruses. In this chapter, we describe various assays used to detect and quantitate the antimicrobial activities of eosinophil granule proteins, particularly ECP and EDN. We have taken a model organism for each assay and described the method for antiviral, antihelminthic, antiprotozoan, and antibacterial activity of purified eosinophil granule proteins.

Infektionsimmunologie

Im Laufe der Entwicklung der Lebewesen traten die Organismen gegeneinander in Konkurrenz und entdeckten andere Spezies als eigene Lebensgrundlage oder Nahrung. Bei höheren Lebewesen sehen wir dies als selbstverständlich an und teilen Sie in Fleisch- und Pflanzenfresser ein. Bei niederen Lebewesen bezeichnen wir dies jedoch als pathogene Eigenschaft oder als parasitäre Lebensweise, wenn wir ihnen als Nahrungsgrundlage dienen (Abb. 8.1). Zur Abwehr der Krankheitserreger entwickelten alle höheren Lebewesen ein Immunsystem, um das Fortbestehen der Spezies zu garantieren. Je weiter sich die Lebewesen entwickelt haben, desto höher hat sich auch das Immunsystem in einer Coevolution in Konkurrenz zu den Erregern entwickelt. Da das Immunsystem in der Evolution zur Infektionsabwehr entstanden ist, leiten sich seine übrigen physiologischen und pathophysiologischen Mechanismen von denen der Infektionsabwehr ab.

Polymorphisms in the RNASE3 gene are associated with susceptibility to cerebral malaria in Ghanaian children

Background

Cerebral malaria (CM) is the most severe outcome of Plasmodium falciparum infection and a major cause of death in children from 2 to 4 years of age. A hospital based study in Ghana showed that P. falciparum induces eosinophilia and found a significantly higher serum level of eosinophil cationic protein (ECP) in CM patients than in uncomplicated malaria (UM) and severe malaria anemia (SA) patients. Single nucleotide polymorphisms (SNPs) have been described in the ECP encoding-gene (RNASE3) of which the c.371G>C polymorphism (rs2073342) results in an arginine to threonine amino acid substitution p.R124T in the polypeptide and abolishes the cytotoxicity of ECP. The present study aimed to investigate the potential association between polymorphisms in RNASE3 and CM.

Methodology/Principal Findings

The RNASE3 gene and flanking regions were sequenced in 206 Ghanaian children enrolled in a hospital based malaria study. An association study was carried out to assess the significance of five SNPs in CM (n = 45) and SA (n = 56) cases, respectively. The two severe case groups (CM and SA) were compared with the non-severe control group comprising children suffering from UM (n = 105). The 371G allele was significantly associated with CM (p = 0.00945, OR = 2.29, 95% CI = 1.22–4.32) but not with SA. Linkage disequilibrium analysis demonstrated significant linkage between three SNPs and the haplotype combination 371G/*16G/*94A was strongly associated with susceptibility to CM (p  = 0.000913, OR = 4.14, 95% CI = 1.79–9.56), thus, defining a risk haplotype. The RNASE3 371GG genotype was found to be under frequency-dependent selection.

Conclusions/Significance

The 371G allele of RNASE3 is associated with susceptibility to CM and forms part of a risk associated haplotype GGA defined by the markers: rs2073342 (G-allele), rs2233860 (G-allele) and rs8019343 (A-allele) respectively. Collectively, these results suggest a hitherto unrecognized role for eosinophils in CM pathogenesis.

Synthesis of heparin oligosaccharides and their interaction with eosinophil-derived neurotoxin

A convenient route for the synthesis of heparin oligosaccharides involving regioselective protection of D-glucosamine and a concise preparation of rare L-ido sugars from diacetone α-D-glucose is described. Stereoselective coupling of a D-glucosamine-derived trichloroacetimidate with a 1,6-anhydro-β-L-idopyranosyl 4-alcohol gave the desired α-linked disaccharide, which was used as repeating unit for dual chain elongation and termination. Stepwise assembly from the reducing to the non-reducing end with a D-glucosamine-derived monosaccharide as starting unit furnished the oligosaccharide skeletons having different chain lengths. A series of functional group transformations afforded the expected heparin oligosaccharides with 3, 5 and 7 sugar units. Interaction of these oligosaccharides with eosinophil-derived neurotoxin (EDN), a cationic ribonuclease and a mediator produced by human eosinophils, was further investigated. The results revealed that at 5 μg mL(-1), the heptasaccharide has sufficiently strong interference to block EDN binding to Beas-2B cells. The tri- and pentasaccharides have moderate inhibitory properties at 50 μg mL(-1) concentration, but no inhibition has been observed at 10 μg mL(-1). The IC(50) values of the tri-, penta- and heptasaccharides are 69.4, 47.2 and 0.225 μg mL(-1), respectively.

MEDI-563, a humanized anti-IL-5 receptor alpha mAb with enhanced antibody-dependent cell-mediated cytotoxicity function

BACKGROUND

Peripheral blood eosinophilia and lung mucosal eosinophil infiltration are hallmarks of bronchial asthma. IL-5 is a critical cytokine for eosinophil maturation, survival, and mobilization. Attempts to target eosinophils for the treatment of asthma by means of IL-5 neutralization have only resulted in partial removal of airway eosinophils, and this warrants the development of more effective interventions to further explore the role of eosinophils in the clinical expression of asthma.

OBJECTIVE

We sought to develop a novel humanized anti-IL-5 receptor alpha (IL-5Ralpha) mAb with enhanced effector function (MEDI-563) that potently depletes circulating and tissue-resident eosinophils and basophils for the treatment of asthma.

METHODS

We used surface plasmon resonance to determine the binding affinity of MEDI-563 to FcgammaRIIIa. Primary human eosinophils and basophils were used to demonstrate antibody-dependent cell-mediated cytotoxicity. The binding epitope of MEDI-563 on IL-5Ralpha was determined by using site-directed mutagenesis. The consequences of MEDI-563 administration on peripheral blood and bone marrow eosinophil depletion was investigated in nonhuman primates.

RESULTS

MEDI-563 binds to an epitope on IL-5Ralpha that is in close proximity to the IL-5 binding site, and it inhibits IL-5-mediated cell proliferation. MEDI-563 potently induces antibody-dependent cell-mediated cytotoxicity of both eosinophils (half-maximal effective concentration = 0.9 pmol/L) and basophils (half-maximal effective concentration = 0.5 pmol/L) in vitro. In nonhuman primates MEDI-563 depletes blood eosinophils and eosinophil precursors in the bone marrow.

CONCLUSIONS

MEDI-563 might provide a novel approach for the treatment of asthma through active antibody-dependent cell-mediated depletion of eosinophils and basophils rather than through passive removal of IL-5.

Role of eosinophils and their clinical significance in allergic inflammation

Eosinophils are believed to play roles in the pathophysiology of allergic inflammation, such as bronchial asthma. However, recent studies on anti-interleukin-5 monoclonal antibody treatment of asthmatic patients raised the possibility that eosinophils may play only a limited role. More recent studies established that eosinophils are essentially involved in the development of airway remodeling. Moreover, it is theoretically conceivable that eosinophils are a cellular source of lipid mediators, such as cysteinyl leukotrienes or platelet-activating factor in asthma. Even in the absence of interleukin-5, it is likely that the 'T-helper Type 2 network', including a cascade of vascular cell adhesion molecule-1, intercellular cell adhesion molecule-1, CC chemokines, granulocyte-macrophage colony-stimulating factor, for example, can maintain sufficient eosinophilic infiltration and effector functions, such as superoxide anion generation and degranulation. Long-term studies, wherein tissue eosinophils are eliminated effectively will be required to establish the exact roles of these cells in asthma. Finally, the authors will demonstrate that eosinophils have the potential for not only playing detrimental roles but also beneficial ones.

Granulocytes: effector cells or immunomodulators in the immune response to helminth infection?

Granulocytes are effector cells in defence against helminth infections. We review the current evidence for the role of granulocytes in protective immunity against different helminth infections and note that for each parasite species the role of granulocytes as effector cells can vary. Emerging evidence also points to granulocytes as immunomodulatory cells able to produce many cytokines, chemokines and modulatory factors which can bias the immune response in a particular direction. Thus, the role of granulocytes in an immunomodulatory context is discussed including the most recent data that points to an important role for basophils under this guise.

TNF-alpha mediates eosinophil cationic protein-induced apoptosis in BEAS-2B cells

Background

Eosinophilic granulocytes are important for the human immune system. Many cationic proteins with cytotoxic activities, such as eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN), are released from activated eosinophils. ECP, with low RNase activity, is widely used as a biomarker for asthma. ECP inhibits cell viability and induces apoptosis to cells. However, the specific pathway underlying the mechanisms of ECP-induced cytotoxicity remains unclear. This study investigated ECP-induced apoptosis in bronchial epithelial BEAS-2B cells and elucidated the specific pathway during apoptosis.

Results

To address the mechanisms involved in ECP-induced apoptosis in human BEAS-2B cells, investigation was carried out using chromatin condensation, cleavage of poly (ADP-ribose) polymerase (PARP), sub-G1 distribution in cell cycle, annexin V labeling, and general or specific caspase inhibitors. Caspase-8-dependent apoptosis was demonstrated by cleavage of caspase-8 after recombinant ECP treatment, accompanied with elevated level of tumor necrosis factor alpha (TNF-α). Moreover, ECP-induced apoptosis was effectively inhibited in the presence of neutralizing anti-TNF-α antibody.

Conclusion

In conclusion, our results have demonstrated that ECP increased TNF-α production in BEAS-2B cells and triggered apoptosis by caspase-8 activation through mitochondria-independent pathway.

Effects of antisense interleukin-5 gene transferred by recombinant adeno-associated virus to allergic rats

BACKGROUND AND OBJECTIVE

The accumulation of eosinophils in airways is an important characteristic of asthma. The process is primarily mediated by interleukin-5 (IL-5) secreted by Th2 lymphocytes. This study explored a new approach to asthma therapy in which allergic rats were transfected with the IL-5 antisense gene delivered by the recombinant adeno-associated virus (rAAV-ASIL-5).

METHODS

The viral vector rAAV-ASIL-5 was constructed and the IL-5 antisense gene transfected into allergic rats. The levels of IL-5, IgE, eotaxin and eosinophilic cationic protein (ECP) in sera and bronchoalveolar lavage fluid (BALF) were measured by ELISA. The inflammatory responses in lung tissues were evaluated by histological study.

RESULTS

The levels of IL-5 protein in serum and BALF were significantly decreased in the allergic rats treated with rAAV-ASIL-5 (P < 0.05). Serum ovalbumin-specific IgE was reduced in treated rats compared with untreated rats (P < 0.05). rAAV-ASIL-5 treatment also reduced eosinophils in the peripheral blood and BALF, as well as the ECP and eotaxin levels in serum and BALF (P < 0.05). There was significantly less inflammation in the lungs of rAAV-ASIL-5-treated rats than in those of untreated rats. No obvious pathological damage to the kidneys and livers of the rats treated with rAAV was observed.

CONCLUSIONS

Treatment with rAAV-ASIL-5 inhibited the accumulation of eosinophils and airway inflammation in the rat model of allergic asthma by suppressing IL-5 production. These results suggest that rAAV-ASIL-5-based gene therapy may be used for the treatment of allergic asthma.

Beta2-integrin-mediated adhesion and intracellular Ca2+ release in human eosinophils

Human eosinophils spontaneously adhere to various substrates in the absence of exogenously added activators. In the present study a method was developed for characterizing eosinophil adhesion by measuring changes in impedance. Impedance measurements were performed in HCO(3)-buffered HybriCare medium maintained in a humidified 5% CO(2) incubator at 37 degrees C. Impedance increased by more than 1 kOmega within minutes after eosinophils made contact with the substrate, reaching a peak within 20 min. Blocking mobilization of intracellular [Ca(2+)] that precedes adhesion with BAPTA-AM (10 microM) completely inhibited the rise in impedance as well as the changes in cell shape typically observed in adherent cells. However, lowering the extracellular [Ca(2+)] with 2.5 mM EGTA did not inhibit the increase in impedance. Pretreatment with anti-CD18 antibody to block substrate interactions with beta(2)-integrins, or jasplakinolide (2 microM) to block actin reorganization, abolished the increase in impedance and adherent morphology of the cells. Exposure of eosinophils to the phosphatidylinositol 3 kinase inhibitor LY294002 (5 microM) or treatment with protein kinase C zeta pseudosubstrate to competitively inhibit activity of the enzyme significantly reduced the increase in impedance and inhibited the cell spreading associated with adhesion. These results demonstrate a novel method for measuring eosinophil adhesion and showed that, following formation of a tethered attachment, a rapid increase in intracellular [Ca(2+)] precedes the cytoskeletal rearrangements required for cell shape changes and plasma membrane-substrate interactions associated with adhesion.

Innate antifungal immunity of human eosinophils mediated by a beta 2 integrin, CD11b

Eosinophils produce and release various proinflammatory mediators and also show immunomodulatory and tissue remodeling functions; thus, eosinophils may be involved in the pathophysiology of asthma and other eosinophilic disorders as well as host defense. Several major questions still remain. For example, how do human eosinophils become activated in diseased tissues or at the site of an immune response? What types of host immunity might potentially involve eosinophils? Herein, we found that human eosinophils react vigorously to a common environmental fungus, Alternaria alternata, which is implicated in the development and/or exacerbation of human asthma. Eosinophils release their cytotoxic granule proteins, such as eosinophil-derived neurotoxin and major basic protein, into the extracellular milieu and onto the surface of fungal organisms and kill the fungus in a contact-dependent manner. Eosinophils use their versatile beta(2) integrin molecule, CD11b, to adhere to a major cell wall component, beta-glucan, but eosinophils do not express other common fungal receptors, such as dectin-1 and lactosylceramide. The I-domain of CD11b is distinctively involved in the eosinophils' interaction with beta-glucan. Eosinophils do not react with another fungal cell wall component, chitin. Because human eosinophils respond to and kill certain fungal organisms, our findings identify a previously unrecognized innate immune function for eosinophils. This immune response by eosinophils may benefit the host, but, in turn, it may also play a role in the development and/or exacerbation of eosinophil-related allergic human diseases, such as asthma.

Essential role of phosphoinositide 3-kinase gamma in eosinophil chemotaxis within acute pulmonary inflammation

We and others have established an important role for phosphoinositide-3 kinase gamma (PI3Kgamma) in the chemotactic responses of macrophages and neutrophils. The involvement of this lipid kinase in allergic inflammatory responses is, however, yet to be fully determined. Here we compare wild-type (WT) and PI3Kgamma(-/-) (KO) mice within a model of ovalbumin (OVA) -specific pulmonary inflammation. Upon OVA aerosol challenge, cell influx into the bronchoalveolar lavage (BAL) fluid consisted of neutrophils, macrophages and, more significantly, eosinophils - which are key effector cells in allergic inflammation. Each population was reduced by up to 80% in KO mice, demonstrating a role for PI3Kgamma in cell infiltration into the airways. The mechanism of reduced eosinophilia was analysed within both development and effector stages of the immune response. Comparable levels of OVA-specific T-cell proliferation and immunoglobulin production were established in both strains. Furthermore, no significant differences between WT and KO chemokine production were observed. Having identified the critical point of PI3Kgamma involvement, KO eosinophil chemotactic dysfunction was confirmed in vitro. These data are the first to demonstrate the vital role of PI3Kgamma in acute allergic inflammation. The profound dependency of eosinophils on PI3Kgamma for pulmonary influx identifies this lipid kinase as an attractive target for the pharmacological intervention of asthma.

Molecular mechanisms of cytokine and chemokine release from eosinophils activated by IL-17A, IL-17F, and IL-23: implication for Th17 lymphocytes-mediated allergic inflammation

IL-17A and IL-17F are members of the IL-17 family that play crucial roles in allergic inflammation. Recent studies reported that IL-17A and IL-17F production from a distinct Th lymphocyte subset, Th17, was specifically induced by IL-23, which was produced by dendritic cells and macrophages in response to microbial stimuli. The IL-23-IL-17 axis might therefore provide a link between infections and allergic diseases. In the present study, we investigated the effects of IL-17A, IL-17F, and IL-23, alone or in combination, on cytokine and chemokine release from eosinophils and the underlying intracellular mechanisms. Human eosinophils were found to constitutively express receptors for IL-17A, IL-17F, and IL-23 at the protein level. IL-17A, IL-17F, and IL-23 could induce the release of chemokines GRO-alpha/CXCL1, IL-8/CXCL8, and MIP-1beta/CCL4 from eosinophils, while IL-17F and IL-23 could also increase the production of proinflammatory cytokines IL-1beta and IL-6. Synergistic effects were observed in the combined treatment of IL-17F and IL-23 on the release of proinflammatory cytokines, and the effects were dose-dependently enhanced by IL-23, but not IL-17F. Further investigations showed that IL-17A, IL-17F, and IL-23 differentially activated the ERK, p38 MAPK, and NF-kappaB pathways. Moreover, inhibition of these pathways using selective inhibitors could significantly abolish the chemokine release induced by IL-17A, IL-17F, and IL-23 and the synergistic increases on IL-1beta and IL-6 production mediated by combined treatment of IL-17F and IL-23. Taken together, our findings provide insight for the Th17 lymphocyte-mediated activation of eosinophils via differential intracellular signaling cascades in allergic inflammation.

Eosinophils: biological properties and role in health and disease

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. In this review, the biology of eosinophils is summarized, focusing on transcriptional regulation of eosinophil differentiation, characterization of the growing properties of eosinophil granule proteins, surface proteins and pleiotropic mediators, and molecular mechanisms of eosinophil degranulation. New views on the role of eosinophils in homeostatic function are examined, including developmental biology and innate and adaptive immunity (as well as their interaction with mast cells and T cells) and their proposed role in disease processes including infections, asthma, and gastrointestinal disorders. Finally, strategies for targeted therapeutic intervention in eosinophil-mediated mucosal diseases are conceptualized.

Secondary necrosis in multicellular animals: an outcome of apoptosis with pathogenic implications

In metazoans apoptosis is a major physiological process of cell elimination during development and in tissue homeostasis and can be involved in pathological situations. In vitro, apoptosis proceeds through an execution phase during which cell dismantling is initiated, with or without fragmentation into apoptotic bodies, but with maintenance of a near-to-intact cytoplasmic membrane, followed by a transition to a necrotic cell elimination traditionally called “secondary necrosis”. Secondary necrosis involves activation of self-hydrolytic enzymes, and swelling of the cell or of the apoptotic bodies, generalized and irreparable damage to the cytoplasmic membrane, and culminates with cell disruption. In vivo, under normal conditions, the elimination of apoptosing cells or apoptotic bodies is by removal through engulfment by scavengers prompted by the exposure of engulfment signals during the execution phase of apoptosis; if this removal fails progression to secondary necrosis ensues as in the in vitro situation. In vivo secondary necrosis occurs when massive apoptosis overwhelms the available scavenging capacity, or when the scavenger mechanism is directly impaired, and may result in leakage of the cell contents with induction of tissue injury and inflammatory and autoimmune responses. Several disorders where secondary necrosis has been implicated as a pathogenic mechanism will be reviewed.

Eosinophil-derived neurotoxin acts as an alarmin to activate the TLR2-MyD88 signal pathway in dendritic cells and enhances Th2 immune responses

Eosinophil-derived neurotoxin (EDN) is an eosinophil granule-derived secretory protein with ribonuclease and antiviral activity. We have previously shown that EDN can induce the migration and maturation of dendritic cells (DCs). Here, we report that EDN can activate myeloid DCs by triggering the Toll-like receptor (TLR)2-myeloid differentiation factor 88 signaling pathway, thus establishing EDN as an endogenous ligand of TLR2. EDN activates TLR2 independently of TLR1 or TLR6. When mice were immunized with ovalbumin (OVA) together with EDN or with EDN-treated OVA-loaded DCs, EDN enhanced OVA-specific T helper (Th)2-biased immune responses as indicated by predominant production of OVA-specific interleukin (IL)-5, IL-6, IL-10, and IL-13, as well as higher levels of immunoglobulin (Ig)G1 than IgG2a. Based on its ability to serve as a chemoattractant and activator of DCs, as well as the capacity to enhance antigen-specific immune responses, we consider EDN to have the properties of an endogenous alarmin that alerts the adaptive immune system for preferential enhancement of antigen-specific Th2 immune responses.

Regulation of the Il4 gene is independently controlled by proximal and distal 3' enhancers in mast cells and basophils

Mast cells and basophils are known to be a critical interleukin 4 (IL-4) source for establishing Th2 protective responses to parasitic infections. Chromatin structure and histone modification patterns in the Il13/Il4 locus of mast cells were similar to those of IL-4-producing type 2 helper T cells. However, using a transgenic approach, we found that Il4 gene expression was distinctly regulated by individual cis regulatory elements in cell types of different lineages. The distal 3' element contained conserved noncoding sequence 2 (CNS-2), which was a common enhancer for memory phenotype T cells, NKT cells, mast cells, and basophils. Targeted deletion of CNS-2 compromised production of IL-4 and several Th2 cytokines in connective-tissue-type and immature-type mast cells but not in basophils. Interestingly, the proximal 3' element containing DNase I-hypersensitive site 4 (HS4), which controls Il4 gene silencing in T-lineage cells, exhibited selective enhancer activity in basophils. These results indicate that CNS-2 is an essential enhancer for Il4 gene transcription in mast cell but not in basophils. The transcription of the Il4 gene in mast cells and basophils is independently regulated by CNS-2 and HS4 elements that may be critical for lineage-specific Il4 gene regulation in these cell types.

Eosinophils and asthma

Recruitment and activation of eosinophils into the airways of asthma patients is suggested to be a contributing causative agent in the histopathologies and lung dysfunction that are characteristic of asthma. Recent studies in mouse models of asthma and in human patients implicate eosinophils in immune regulation and remodeling in the lung in addition to their hypothesized role as destructive agents. Specifically, eosinophils not only participate in release of granule proteins, lipid mediators, reactive oxygen species, cytokines, and growth factors but also function through complex cell-cell interactions to elicit chronic T helper 2 inflammation in the lung. This review highlights the roles of eosinophils in asthma.

The 434(G>C) polymorphism within the coding sequence of Eosinophil Cationic Protein (ECP) correlates with the natural course of Schistosoma mansoni infection

Schistosomiasis is a chronic parasitic infection with over 200 million people infected worldwide. In Schistosoma mansoni infections, parasite-derived eggs get trapped in the liver, causing the formation of granulomas, which may develop into periportal fibrosis and portal hypertension, and thus severe morbidity. Eosinophil cationic protein (ECP) is a secretory protein of eosinophil granulocytes that efficiently kills the larval stage of S. mansoni, but also affects fibroblast functions. We have investigated the prevalence of the ECP gene polymorphism 434(G>C) in two African populations, from an S. mansoni endemic area in Uganda (n=297) and from a non-endemic area in Sudan (n=78), and also compared these with a Swedish population (n=209). The genotype frequencies in the Ugandan population differed significantly from both the Sudanese and Swedish populations (P<0.001). In the Ugandan population there was a significant association between genotype and prevalence of infection (P=0.03), with lower prevalence in subjects with the GG genotype compared with GC (P=0.02) and CC (P=0.03). There was also a trend towards an association with periportal fibrosis (P=0.08) in the Ugandan population. This suggested association was confirmed when the predominant tribe (n=212) was analysed separately (P=0.004). Our results suggest that ECP may be an important protein, both in the immune response against S. mansoni and in the development of periportal fibrosis. The results also suggest genetic selection towards the ECP 434CC genotype in populations living in S. mansoni endemic areas.

Induction of adhesion molecules upon the interaction between eosinophils and bronchial epithelial cells: involvement of p38 MAPK and NF-kappaB

Eosinophils are principal effector cells of inflammation in allergic asthma, characterized by their infiltration and accumulation at inflammatory sites mediated by chemokine eotaxin, and interaction with adhesion molecules expressed on bronchial epithelial cells. In this study, tumor necrosis factor (TNF)-alpha and/or the interaction of eosinophils and bronchial epithelial BEAS-2B cells were found to up-regulate the cell surface expression of adhesion molecules intercellular adhesion molecule (ICAM)-1 and vascular adhesion molecule (VCAM)-1 on BEAS-2B cells, and ICAM-1 and leukocyte function-associated antigen-1 (LFA-1) on eosinophils. Interaction of eosinophils and BEAS-2B cells could induce the release of granulocyte macrophage colony-stimulating factor (GM-CSF) and activate both p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB activities in BEAS-2B cells but only NF-kappaB activity in eosinophils. Both proteasome inhibitor MG-132 and selective p38 MAPK inhibitor SB 203580 could significantly decrease the expression of ICAM-1 on BEAS-2B cells and CD18 on eosinophils upon co-culture with or without TNF-alpha treatment. However, the expression of VCAM-1 on BEAS-2B cells was only up-regulated by TNF-alpha-induced NF-kappaB activity. The interaction of eosinophils and bronchial epithelial cells therefore plays an important role in the up-regulation of adhesion molecules on eosinophils and epithelial cells via differential intracellular signalling pathways during allergic inflammation.

Eosinophil cationic protein damages protoscoleces in vitro and is present in the hydatid cyst

Eosinophils are locally recruited during the establishment and chronic phases of cystic hydatidosis. This study provides evidence that eosinophil cationic protein (ECP), one of the major components of eosinophil granules, can damage Echinococcus granulosus protoscoleces (PSC). The toxicity of ECP was investigated in vitro by following parasite viability in the presence of this protein. ECP was found to damage PSC at micromolar concentrations; the effect was blocked by specific antibodies and heparin, and was more severe than the one caused by similar concentrations of RNase A, suggesting that the cationic nature of ECP, and not its ribonuclease activity, is involved in toxicity. This observation may highlight the capacity of eosinophils to control secondary hydatidosis, derived from PSC leakage from a primary cyst. To further assess the relevance of the previous result during infection, the presence of eosinophil proteins was investigated in human hydatid cysts. ECP was found to be strongly associated with the laminated layer of the cyst wall, and present at micromolar concentrations in the hydatid fluid. Overall, these results demonstrate that eosinophils degranulate in vivo at the host-parasite interface, and that the released ECP reaches concentrations that could be harmful for the parasite.

CD8 T cells modulate CD4 T-cell and eosinophil-mediated pulmonary pathology in pneumocystis pneumonia in B-cell-deficient mice

Pneumocystis spp. pneumonia (PCP) in humans and in surrogate animal species typically occurs in the absence of CD4 T cells, as takes place during acquired immune deficiency syndrome. However, patients treated with highly active anti-retroviral therapy sometimes exhibit an exacerbation of diseases such as PCP that coincides with resurgent CD4 T cells, a phenomenon known as immune reconstitution disease. We used an animal model of PCP using the B-cell-deficient muMT mouse together with antibody-mediated depletion of various T-cell subsets to examine the role of CD4 and CD8 T cells in the development of pathology in PCP. Although overt pathology occurs in the presence of CD4 T cells only, CD8 T cells only, or both, pulmonary injury occurs via different paths, depending on the complement of T cells present. Surprisingly, profound damage occurred when only CD4 T cells were present, and this pathology coincided with enhanced recruitment and activation of eosinophils and strong type 2 cytokine polarization in the alveolar environment. In addition, CD8 T cells can act to moderate this CD4 T cell-mediated pathology, possibly by increasing the ratio of putative CD25+ suppressor CD4 T cells to CD25- effector CD4 T cells.

T cell and eosinophil activation in mild and moderate atopic and nonatopic children's asthma in remission

BACKGROUND

Inflammation in the pathogenesis of asthma is associated with products of activated T cells and eosinophils. The aim of this study was to determine whether ongoing inflammation persists in children with different phenotypes of asthma despite the disease in remission.

METHODS

Serum samples were collected from 68 children with atopic or nonatopic asthma in remission and from 15 healthy children. Soluble interleukin-2 receptor (sIL-2R), IL-2 and IL-4 were examined by using an enzyme-linked immunosorbent assay. Total and specific immunoglobulin E, and eosinophil cationic protein (ECP) were analysed by fluoroimmunoassay (Pharmacia CAP System).

RESULTS

In patients with moderate persistent atopic asthma, sIL-2R was increased significantly when compared with mild persistent atopic asthma (P < 0.05). No changes of sIL-2R were seen in nonatopic asthmatics compared with atopics and controls. The level of IL-2 was elevated in moderate persistent atopic and nonatopic asthmatic children compared with controls (P < 0.05 and P < 0.05 respectively) and compared with mild persistent atopic asthmatics and mild persistent nonatopic asthmatics (P < 0.05 in both cases). The levels of IL-4 in most patients and controls remained below the sensitivity of the assay. Eosinophil cationic protein levels in moderate persistent atopic and nonatopic asthmatics were significantly higher than in mild persistent asthma severity cases (P < 0.001 and P < 0.01 respectively) and in healthy children (P < 0.01 in both cases).

CONCLUSION

Changes in the concentration of sIL-2R, IL-2 and ECP reflect increased T cell and eosinophil activity in relation to the level of severity of asthma in atopic and nonatopic children, thereby proving the presence of persistent inflammation despite the absence of disease symptoms.

Activation of humoral immunity and eosinophils in neuromyelitis optica

OBJECTIVE

To study immunologic alterations in patients with neuromyelitis optica (NMO).

METHODS

The authors studied 8 patients with NMO together with 16 healthy subjects, 16 patients with relapsing remitting multiple sclerosis (RRMS), and 16 patients with secondary progressive MS (SPMS), matched for age and sex, as controls. Because recent histopathologic studies have demonstrated that active NMO lesions consist of perivascular immunoglobulin (Ig) deposition and eosinophil infiltration, IL-5, IL-6, IL-12, IgG, and IgM production by anti-myelin oligodendrocyte glycoprotein (MOG) mononuclear cells in peripheral blood and CSF were selected for study using ELISPOT. Eotaxin-2 (Eo-2) and eotaxin-3 (Eo-3) levels were also assessed using ELISA and eosinophil cationic protein (ECP) levels by radioimmunoassay.

RESULTS

MOG-specific responses in CSF showed significant increase in IL-5, IL-6, IgG, and IgM secreting cells in NMO patients compared with patients with RRMS, SPMS and healthy subjects. Interestingly, numbers of IgM secreting cells were significantly higher than identical specificity IgG secreting ones. Moreover, CSF Eo-2, Eo-3, and ECP levels were also significantly higher in NMO patients compared to all three control populations. Anti-MOG IL-12 secreting cells were increased in CSF and peripheral blood from NMO, RRMS, and SPMS patients when compared to healthy subjects.

CONCLUSIONS

These observations suggest that neuromyelitis optica is associated with a major humoral immune response (particularly anti-MOG IgM production) and eosinophil activation present exclusively in CSF.