Eosinophil infiltration precedes development of airway hyperreactivity and mucosal exudation after intranasal administration of interleukin-5 to mice

Basophils Orchestrating Eosinophils' Chemotaxis and Function in Allergic Inflammation

Eosinophils are well known to contribute significantly to Th2 immunity, such as allergic inflammations. Although basophils have often not been considered in the pathogenicity of allergic dermatitis and asthma, their role in Th2 immunity has become apparent in recent years. Eosinophils and basophils are present at sites of allergic inflammations. It is therefore reasonable to speculate that these two types of granulocytes interact in vivo. In various experimental allergy models, basophils and eosinophils appear to be closely linked by directly or indirectly influencing each other since they are responsive to similar cytokines and chemokines. Indeed, basophils are shown to be the gatekeepers that are capable of regulating eosinophil entry into inflammatory tissue sites through activation-induced interactions with endothelium. However, the direct evidence that eosinophils and basophils interact is still rarely described. Nevertheless, new findings on the regulation and function of eosinophils and basophils biology reported in the last 25 years have shed some light on their potential interaction. This review will focus on the current knowledge that basophils may regulate the biology of eosinophil in atopic dermatitis and allergic asthma.

Long noncoding RNA atlas of the inflammation caused by asthma in mice

There is little evidence regarding the roles of long noncoding RNAs (lncRNAs) in inflammation caused by asthma. In this study, we successfully generated an asthma mouse model that was induced by ovalbumin (OVA). The effects of dexamethasone (Dex) treatment on lung tissue were investigated using pathological and biochemical methods, including Diff-Quik staining, enzyme-linked immunosorbent assay (ELISA), hematoxylin-eosin (H&E) staining, and western blotting (WB). The inflammation was effectively relieved with Dex treatment. High-throughput sequencing revealed that a total of 1490 lncRNAs were detected in lung tissue samples. Differential expression analysis revealed that the Dex group had 20 upregulated and 15 downregulated lncRNAs compared with those in the Model group. Moreover, nine differentially expressed and inflammation-related lncRNAs were verified by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Furthermore, the regulation networks of these nine lncRNAs, their potential binding microRNA (miRNAs), and the putative target genes showed that these lncRNAs play important roles in the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. We further identified the expression levels of three potential binding miRNAs by qRT-PCR. The results of this study contribute to a better understanding of the functions of lncRNAs in inflammation caused by asthma.

Single and Synergistic Effects of Type 2 Cytokines on Eosinophils and Asthma Hallmarks

The type 2 cytokines IL-5, IL-13, and IL-4 play an important role in the induction and progression of asthma. According to the Global Initiative for Asthma guidelines, blood eosinophil numbers are one marker that helps to guide treatment decisions in patients suffering from severe forms of asthma. Effects of type 2 cytokines were analyzed, alone or in combination, on eosinophils in blood and other compartments and on the development of asthma symptoms. C57BL/6 mice received a single intranasal application of equimolar amounts of IL-5, IL-13, and IL-4, alone or in combination. Numbers, activation state, and migratory behavior of eosinophils in bone marrow (BM), blood, lung, and bronchoalveolar lavage as well as airway hyperresponsiveness and goblet cell metaplasia were evaluated. Only IL-13 was associated with airway eosinophilia, development of airway hyperresponsiveness, and goblet cell metaplasia, without any synergistic effects. IL-5 increased the number of eosinophils in BM and lung tissue but failed to affect structural changes. IL-4 had similar, but weaker, effects to IL-13. Cytokine combinations synergistically affected eosinophils but failed to enhance IL-13-driven effects on lung function or goblet cell metaplasia. IL-5 and IL-13 markedly increased eosinophil numbers locally in lung and airways and distally in blood and BM, whereas IL-5 and IL-4 only increased eosinophils in lung and BM. IL-13 together with IL-4 failed to demonstrate any synergistic effect. These insights into single and combined effects of type 2 cytokines on disease-driving mechanisms could improve understanding of the impact and effectiveness of new therapies in asthma.

Historic overview of allergy research in the Netherlands

Research in allergy has a long history in the Netherlands, although the relation with immunology has not always been appreciated. In many aspects Dutch researchers have made major contribution in allergy research. This ranges from the first characterization of house dust mite as an important allergen, the first characterization of human Th2 and Th1 T cell clones, to the development of diagnostic test systems. In this overview Aalberse and Knol have made an overview of the major contributions of Dutch immunologists in allergy.

Thymic Stromal Lymphopoietin Enhances Th2/Th22 and Reduces IL-17A in Protease-Allergen-Induced Airways Inflammation

Background. Thymic stromal lymphopoietin (TSLP) is induced in allergic skin and lung inflammation in man and mice. Methods. Allergic lung inflammation induced by two proteases allergens HDM and papain and a classical allergen ovalbumin was evaluated in vivo in mice deficient for TSLPR. Eosinophil recruitment, Th2 and Th17 cytokine and chemokine levels were determined in bronchoalveolar lavage fluid, lung homogenates and lung mononuclear cells ex vivo. Results. Here we report that mice challenged with house dust mite extract or papain in the absence of TSLPR have a drastic reduction of allergic inflammation with diminished eosinophil recruitment in BAL and lung and reduced mucus overproduction. TSLPR deficient DCs displayed diminished OVA antigen uptake and reduced capacity to activate antigen specific T cells. TSLPR deficient mice had diminished proinflammatory IL-1 β , IL-13, and IL-33 chemokines production, while IL-17A, IL-12p40 and IL-10 were increased. Together with impaired Th2 cytokines, IL-17A expressing TCR β (+) T cells were increased, while IL-22 expressing CD4(+) T cells were diminished in the lung. Conclusion. Therefore, TSLPR signaling is required for the development of both Th2 and Th22 responses and may restrain IL-17A. TSLP may mediate its effects in part by increasing allergen uptake and processing by DCs resulting in an exacerbated asthma.

Th2 cytokine antagonists: potential treatments for severe asthma

INTRODUCTION

Asthma is a major disease burden worldwide. Treatment with steroids and long acting β-agonists effectively manage symptoms in many patients but do not treat the underlying cause of disease and have serious side effects when used long term and in children. Therapies targeting the underlying causes of asthma are urgently needed. T helper type 2 (Th2) cells and the cytokines they release are clinically linked to the presentation of all forms of asthma. They are the primary drivers of mild to moderate and allergic asthma. They also play a pathogenetic role in exacerbations and more severe asthma though other factors are also involved. Much effort using animal models and human studies has been dedicated to the identification of the pathogenetic roles of these cells and cytokines and whether inhibition of their activity has therapeutic benefit in asthma.

AREAS COVERED

We discuss the current status of Th2 cytokine antagonists for the treatment of asthma. We also discuss the potential for targeting Th2-inducing cytokines, Th2 cell receptors and signaling as well as the use of Th2 cell antagonists, small interfering oligonucleotides, microRNAs, and combination therapies.

EXPERT OPINION

Th2 antagonists may be most effective in particular asthma subtypes/endotypes where specific cytokines are known to be active through the analysis of biomarkers. Targeting common receptors and pathways used by these cytokines may have additional benefit. Animal models have been valuable in identifying therapeutic targets in asthma, however the results from such studies need to be carefully interpreted and applied to appropriately stratified patient cohorts in well-designed clinical studies and trials.

Cytokine/anti-cytokine therapy - novel treatments for asthma?

Asthma is a chronic inflammatory disease of the airways and there are no preventions or cures. Inflammatory cells through the secretion of cytokines and pro-inflammatory molecules are thought to play a critical role in pathogenesis. Type 2 CD4(+) lymphocytes (Th2 cells) and their cytokines predominate in mild to moderate allergic asthma, whereas severe steroid-resistant asthma has more of a mixed Th2/Th1 phenotype with a Th17 component. Other immune cells, particularly neutrophils, macrophages and dendritic cells, as well structural cells such as epithelial and airway smooth muscle cells also produce disease-associated cytokines in asthma. Increased levels of these immune cells and cytokines have been identified in clinical samples and their potential role in disease demonstrated in studies using mouse models of asthma. Clinical trials with inhibitors of cytokines such as interleukin (IL)-4, -5 and tumour necrosis factor-α have had success in some studies but not others. This may reflect the design of the clinical trials, including treatments regimes and the patient population included in these studies. IL-13, -9 and granulocyte-macrophage colony-stimulating factor are currently being evaluated in clinical trials or preclinically and the outcome of these studies is eagerly awaited. Roles for IL-25, -33, thymic stromal lymphopoietin, interferon-γ, IL-17 and -27 in the regulation of asthma are just emerging, identifying new ways to treat inflammation. Careful interpretation of results from mouse studies will inform the development and application of therapeutic approaches for asthma. The most effective approaches may be combination therapies that suppress multiple cytokines and a range of redundant and disconnected pathways that separately contribute to asthma pathogenesis. Astute application of these approaches may eventually lead to the development of effective asthma therapeutics. Here we review the current state of knowledge in the field.

CD4+CD25-mTGFbeta+ T cells induced by nasal application of ovalbumin transfer tolerance in a therapeutic model of asthma

BACKGROUND

Intranasal administration of high amount of allergen was shown to induce tolerance and to reverse the allergic phenotype. However, mechanisms of tolerance induction via the mucosal route are still unclear.

OBJECTIVES

To characterize the therapeutic effects of intranasal application of ovalbumin (OVA) in a mouse model of bronchial inflammation as well as the cellular and molecular mechanisms leading to protection upon re-exposure to allergen.

METHODS

After induction of bronchial inflammation, mice were treated intranasally with OVA and re-exposed to OVA aerosols 10 days later. Bronchoalveolar lavage fluid (BALF), T cell proliferation and cytokine secretion were examined. The respective role of CD4(+)CD25(+) and CD4(+)CD25(-) T cells in the induction of tolerance was analysed.

RESULTS

Intranasal treatment with OVA drastically reduced inflammatory cell recruitment into BALF and bronchial hyperresponsiveness upon re-exposure to allergen. Both OVA- specific-proliferation of T cells, T(h)1 and T(h)2 cytokine production from lung and bronchial lymph nodes were inhibited. Transfer of CD4(+)CD25(-) T cells, which strongly expressed membrane-bound transforming growth factor β (mTGFβ), from tolerized mice protected asthmatic recipient mice from subsequent aerosol challenges. The presence of CD4(+)CD25(+)(Foxp3(+)) T cells during the process of tolerization was indispensable to CD4(+)CD25(-) T cells to acquire regulatory properties. Whereas the presence of IL-10 appeared dispensable in this model, the suppression of CD4(+)CD25(-)mTGFβ(+) T cells in transfer experiments significantly impaired the down-regulation of airways inflammation.

CONCLUSION

Nasal application of OVA in established asthma led to the induction of CD4(+)CD25(-)mTGFβ(+) T cells with regulatory properties, able to confer protection upon allergen re-exposure.

Interleukin-22 is a negative regulator of the allergic response

A proinflammatory role of T helper (Th)17 cells, producing IL-22 and IL-17A, has been favored although there is evidence for negative immune regulation by IL-17A. Here we show that IL-22 was produced during an allergic response in lungs of mice, immunized and challenged with ovalbumin (OVA), and that IL-22 neutralization further augmented the eosinophil recruitment to the lung. In a second allergy model, transfer of OVA-pulsed dendritic cells (DC) into naive mice conveyed eosinophil recruitment in response to subsequent inhaled OVA challenge, while DC preincubation with recombinant IL-22 abolished this response. Similarly, DC preincubation with IL-17A abolished DC-driven eosinophil recruitment, showing that both Th17 cytokines IL-22 and IL-17A mediate negative regulation of allergy by acting on DCs. Therefore, IL-22 inhibits DC functions and attenuates an allergic response.

A role for Bid in eosinophil apoptosis and in allergic airway reaction

Bid, a proapoptotic member of Bcl-2 family, is involved in Fas receptor signaling. Fas activation promotes human eosinophil cell death and is believed to accelerate the resolution of pulmonary Th2-driven allergic reaction in mice. We hypothesized that Bid would regulate eosinophil apoptosis and Ag-induced airway inflammation, particularly eosinophilia. C57BL/6 Bid(-/-) and wild-type mice were immunized and repeatedly challenged with OVA, and bronchoalveolar lavage (BAL) fluid, lung, and spleen were collected 4-240 h after the final challenge. Cultured BAL eosinophils from Bid-deficient mice showed resistance to Fas-mediated apoptotic DNA fragmentation, phosphatidylserine exposure, mitochondria depolarization, and caspase-3 activity. In addition, OVA-challenged Bid(-/-) mice had higher BAL eosinophilia and a lower proportion of BAL apoptotic eosinophils than Bid(+/+) mice. This was accompanied by augmented BAL levels of the eosinophilotactic cytokine, IL-5, and of the eosinophil-associated mediators, TGF-beta1 and fibronectin. Finally, cultured OVA-stimulated lung mononuclear cells and splenocytes from Bid-deficient mice showed increased release of the Th2-type cytokines, IL-4 and IL-5, but no change in cell number. We conclude that Bid modulates BAL eosinophilia by regulating both eosinophil apoptosis and Th2-type cytokine production.

Interleukin-17 is a negative regulator of established allergic asthma

T helper (Th)17 cells producing interleukin (IL)-17 play a role in autoimmune and allergic inflammation. Here, we show that IL-23 induces IL-17 in the lung and IL-17 is required during antigen sensitization to develop allergic asthma, as shown in IL-17R–deficient mice. Since IL-17 expression increased further upon antigen challenge, we addressed its function in the effector phase. Most strikingly, neutralization of IL-17 augmented the allergic response in sensitized mice. Conversely, exogenous IL-17 reduced pulmonary eosinophil recruitment and bronchial hyperreactivity, demonstrating a novel regulatory role of IL-17. Mechanistically, IL-17 down modulated eosinophil-chemokine eotaxin (CCL11) and thymus- and activation-regulated chemokine/CCL17 (TARC) in lungs in vivo and ex vivo upon antigen restimulation. In vitro, IL-17 reduced TARC production in dendritic cells (DCs)—the major source of TARC—and antigen uptake by DCs and IL-5 and IL-13 production in regional lymph nodes. Furthermore, IL-17 is regulated in an IL-4–dependent manner since mice deficient for IL-4Rα signaling showed a marked increase in IL-17 concentration with inhibited eosinophil recruitment. Therefore, endogenous IL-17 is controlled by IL-4 and has a dual role. Although it is essential during antigen sensitization to establish allergic asthma, in sensitized mice IL-17 attenuates the allergic response by inhibiting DCs and chemokine synthesis.

Antiasthmatic activity and selective inhibition of type 2 helper T cell response by aqueous extract of semen armeniacae amarum

Semen armeniacae amarum (SAA) has long been used to control asthma in Korean traditional medicine. However, its antiasthmatic action still remains poorly understood. In the current study, effective mechanism of SAA was investigated in a mouse model of allergic asthma induced by repeated sensitization and intranasal challenge with OVA. Airway hyperreactivity (AHR) measured by beta-methacholine-induced airflow obstruction and airway recruitment of leukocytes including eosinophils were significantly reduced by oral treatment of SAA water extract. Level of interleukin (IL)-4, but not Interferon gamma (IFN-gamma), in the bronchoalveolar lavage fluid (BALF) also appeared considerably lower in SAA-treated mice than in controls. Collectively, these data show that SAA suppresses type 2 helper T cell (Th2), but not type 1 helper T cell (Th1), response. This hypothesis was supported further by the data of ex vivo cytokine production of peribronchial lymph node cells. Thus, oral administration of SAA attenuates asthmatic manifestations including AHR and airway inflammation, which possibly result from selective inhibition of Th2 response to allergen. Our data strongly suggest that SAA may be effectively applied to control other Th2-related diseases as well as allergic asthma.

IL-19 induced Th2 cytokines and was up-regulated in asthma patients

IL-19 belongs to the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, melanoma differentiation-associated gene-7 (IL-24), and AK155 (IL-26). IL-10 has been shown to inhibit allergen-induced airway hyperreactivity and inflammation. To determine whether IL-19 was also associated with asthma, we used ELISA to analyze the serum level of IL-19 in patients with asthma and found that their serum IL-19 levels were twice those of healthy controls. Patients with a high level of IL-19 also had high levels of IL-4 and IL-13. In a dust mite-induced murine model of asthma, we found that IL-19 level in asthmatic BALB/cJ mice was also twice that of healthy control mice. IL-19 transcript was also induced in the lungs of asthmatic mice. Electroporation i.m. of the IL-19 gene into healthy mice up-regulated IL-4 and IL-5, but not IL-13. However, IL-19 up-regulated IL-13 in asthmatic mice. In vitro, IL-19 induced IL-4, IL-5, IL-10, and IL-13 production by activated T cells. Activation of T cells was required for induction of IL-13 because IL-19 did not induce IL-13 production on nonstimulated T cells. Taken together, these results demonstrated that IL-19 up-regulates Th2 cytokines on activated T cells and might play an important role in the pathogenesis of asthma.

Resiquimod, a new immune response modifier from the family of imidazoquinolinamines, inhibits allergen-induced Th2 responses, airway inflammation and airway hyper-reactivity in mice

BACKGROUND

Allergen-induced sensitization and airway disease are the results of adverse immune reactions against environmental antigens that may be prevented or inhibited by immune modifying strategies.

OBJECTIVE

To investigate the effects of the novel immune response modifier resiquimod (R-848), from the family of imidazol-derivates, in a murine model of allergen-mediated Th2-immune responses and concomitant airway inflammation and airway hyper-reactivity.

METHODS

BALB/c mice were systemically sensitized with ovalbumin (OVA) on days 1 and 14 and challenged with OVA aerosol on days 28 and 29. R-848 was applied intranasally to sensitized animals once prior to the first allergen airway challenge, on day 27.

RESULTS

A single application of R-848 significantly reduced numbers of eosinophils and lymphocytes in bronchoalveolar lavage fluid and inhibited mucus gland hyperplasia, compared with sensitized and challenged controls. Associated with the decrease in airway inflammation, single intranasal treatment with R-848 abolished the development of airway hyper-reactivity after allergen sensitization and airway challenges. Additionally, Th2-cytokine production in lung tissues from sensitized and R-848-treated animals was reduced, whereas IL-12 and IFN-gamma production was increased, compared with non-treated sensitized mice.

CONCLUSION

These data indicate that R-848 effectively inhibits allergen-induced airway inflammation and hyper-reactivity by modulation of increased Th2-immune responses.

Animal models of type I allergy using recombinant allergens

Various animal models including guinea pigs, monkeys, dogs, rats, and mice have been established in an attempt to provide insights into the complex immunological and pathophysiological mechanisms of human type I allergic diseases. The detailed knowledge of the murine genome, the various components of the murine immune system, and the generation of engineered mice has made the murine system the most attractive among all animal models. The availability of multitude technologies and reagents to characterize and manipulate immunological pathways and mediators adds to the outstanding opportunities to assess the pathology of allergic diseases and to develop novel therapeutic strategies in mice. Numerous sensitization protocols with food and aero-allergens are used to establish an allergic/asthma-like phenotype in mice. Requirements for an appropriate murine model include a close resemblance to the pathology of the disease in humans, the objective measurement of the physiologic parameters, as well as reliability and reproducibility of the experimental data. With respect to reproducible experimental conditions, it has been recognized that extract preparations from natural allergen sources can vary in their allergen-content and -composition. This might influence the degree of sensitization or the outcome of treatment strategies in dependence of the applied extract preparation. The use of recombinant allergens in experimental in vivo and in vitro systems can overcome these problems. Another aspect, that has become obvious from the experimental studies, is that allergens can differ in their immunogenicity as well as in their capacity to act as tolerogens. Therefore, it seems important that the efficacy of the different allergen-molecules to act as therapeutic agents is individually examined. In this review, examples of animal models are described, in which recombinant allergens have been used for sensitization and/or treatment of allergic responses and how they have been used to enhance our understanding of the pathology of allergic diseases.

To respond or not to respond: T cells in allergic asthma

The incidence of allergic asthma has almost doubled in the past two decades. Numerous epidemiological studies have linked the recent surge in atopic disease with decreased exposure to infections in early childhood as a result of a more westernized lifestyle. However, a clear mechanistic explanation for how this might occur is still lacking. An answer might lie in the presently unfolding story of various regulatory T-cell populations that can limit adaptive immune responses, including T helper 2 (T(H)2)-cell-mediated allergic airway disease.

Elicitation of the allergic reaction in beta-lactoglobulin-sensitized Balb/c mice: biochemical and clinical manifestations differ according to the structure of the allergen used for challenge

BACKGROUND

Mouse models of allergy are used to study the mechanisms of induction and perpetuation of bronchopulmonary hyper-reactivity (BHR) as related to eosinophils and specific IgE.

OBJECTIVE

Our aim was to adapt the current model for the study of bovine beta-lactoglobulin (BLG), a major cow's milk allergen, and to further analyse the mechanisms of the acute and late allergic reaction.

METHODS

Female Balb/c mice were sensitized intraperitoneally with BLG and the influence of the adjuvant and of the BLG dose on the IgE response was analysed, IgE and IgG1 epitopes being characterized. Once optimized, this model was applied to the study of the active phase of allergy in the respiratory tract after a single airway challenge using native or denatured BLG, which contains only linear epitopes.

RESULTS

An immediate allergic reaction was characterized by the rapid release of histamine into the bronchoalveolar lavage fluids. Prostaglandin (PG)D2 was only present when the standard histamine-releasing agent compound 48/80 or denatured BLG were used as triggers, whereas native BLG induced leukotriene release. Twenty-four hours after challenge, BHR, eosinophil influx, IL-4 and IL-5 production, plasma exudation and mucus production were very much increased, differently depending on the allergen structure, and indicated the occurrence of the late allergic reaction. Our results show that the murine model can be used to study the mechanisms of allergy to clinically relevant antigens, such as those contained in cow's milk. The acute allergic reaction, which depends on the structural feature of the allergen, is composed of two distinct pathways characterized by peptido-leukotrienes or PGD2 production, which may result from distinct activation intensities of mast cells, leading to distinct late reactions.

CONCLUSION

This study thus demonstrates a clear link between the structural feature of a protein, and the physiopathology of the experimental asthmatic reaction.

Therapeutic efficacy of an E coli strain carrying an ovalbumin allergenic peptide as a fused protein to OMPC in a murine model of allergic airway inflammation

An Escherichia coli strain expressing the ovalbumin (OVA) 323-329 allergenic peptide on the bacterial surface was evaluated for its ability to reduce the lung inflammatory response in mice allergic to OVA. BALB/c mice were rendered allergic by means of two intraperitoneal injections of OVA suspended in alum 5 days apart, and one intratracheal boost 1 week later. The mice were then treated with two intranasal, 1 week apart, doses of 4x10(9) E. coli-UH302 transformed with plasmids pST13 or pST13-OVA(323-339), which bear the OmpC porin from Salmonella enterica serovar Typhi or the OmpC with the OVA allergenic 323-339 amino acid sequence inserted in the external loop 5. The allergic inflammatory reaction was evaluated on day 31, finding that mice treated with E. coli-UH302-pST13-OVA reduced four to seven times perivascular and peribronchial infiltrates, mucus production, goblet cell hyperplasia and eosinophils when compared with mice treated with E. coli-UH302-pST13 or saline solution. These results were consistent with a significant decrease of IL-5 mRNA and induction of IFN-gamma mRNA in cells from bronchio-alveolar lavages (BAL). Specific serum IgE anti-OVA was also reduced, although the decrease did not reach statistical significance. These results demonstrate that the bacterial live vector bearing an allergenic peptide successfully moderated two important components of allergy, pulmonary inflammation and mucus overproduction.

Persistence of bronchopulmonary hyper-reactivity and eosinophilic lung inflammation after anti-IL-5 or -IL-13 treatment in allergic BALB/c and IL-4Ralpha knockout mice

BACKGROUND

Antigen-induced bronchopulmonary hyper-reactivity (BHR) is generally associated with eosinophilia. It involves cytokines produced by Th2 lymphocytes, including IL-4, IL-5 and IL-13, which are implicated in IgE production, eosinophil differentiation and attraction, and related events relevant to allergic inflammation, whose mechanisms remain unclear.

OBJECTIVE

To investigate the mechanisms by which Th2 cytokines mediate eosinophilia and subsequent BHR using ovalbumin (OVA)-immunized and OVA-challenged IL-4Ralpha-/- and IL-4-/- mice, which fail to transduce and/or to produce IL-4 and IgE as compared with wild type (WT) mice, and specific neutralizing antibodies.

METHODS

On days 0 and 7, mice were immunized subcutaneously (s.c.) with OVA. At day 14, anti-IL-5 or anti-IL-13 antibodies were administered intranasally and/or intravenously before allergenic challenge. Different functional and cellular parameters were studied in vivo and cytokine production was followed with a newly described ex vivo procedure using lung explants.

RESULTS

IL-4Ralpha-/- and IL-4-/- mice developed BHR and pulmonary eosinophilia, even though eosinophil recruitment to the bronchoalveolar liquid lavage (BALF) was reduced. In vivo, IL-4-/- and IL-4Ralpha-/- mice produced, respectively, no or reduced amounts of IL-5 in the BALF/serum as compared with WT mice, whereas no IL-13 in the BALF was detected. By contrast, ex vivo, surviving lung explants from WT and IL-4-/- or IL-4Ralpha-/- mice produced IL-13 and large amounts of IL-5. The neutralization of IL-5 in vivo (BALF and serum) and ex vivo (from lung explant) in IL-4Ralpha-/- and WT mice failed to suppress BHR and lung eosinophilia, and to modify IL-13 production ex vivo. In addition, neutralization of IL-13 in vivo from lung explant also failed to abrogate BHR and lung eosinophilia, whereas IL-5 was unchanged.

CONCLUSION

Antigen-induced BHR can develop independently from IL-4, IL-5 or IL-13 and from the IL-4alpha receptor chain, suggesting a possible novel IL-4, IL-5 and IL-13-independent pathway for the development of BHR in allergic BALB/c mice. The failure of IL-5 or IL-13 antibodies to prevent BHR in IL-4Ralpha-/- mice suggests that neither is indispensable for BHR but does not exclude a role for lung tissue eosinophilia.

Effects of fractions of traffic particulate matter on TH2-cytokines, IgE levels, and bronchial hyperresponsiveness in mice

In recent decades an increased prevalence of allergic conditions has been observed in developed countries. Although lifestyles, exposure to infection, and diet are all likely important factors, many studies have also shown a strong link between industrialization and allergy. The aim of this study was to investigate which extract fractions from traffic particulate matter (TPM, collected in a tunnel in Prague) have the greatest impact on different inflammatory and immunological parameters, such as cytokine production, levels of immunoglobulin E (IgE) antibodies, and bronchial hyperresponsiveness (BHR) in mice, when the extracts are used together with birch pollen for immunization. BP2 mice were immunized with birch pollen and different fractions of TPM (fractions 1-8). They were provoked intranasally with a mixture of pollen and TPM or pollen alone before they were challenged with methacholine. The BHR was evaluated in a whole-body plethysmograph. Th2 cytokines and fibronectin concentrations were measured, and differential cell counts were performed in the bronchioalveolar lavage (BAL) fluid. Sera were collected for determination of antibody titers. The highest titers of IgE and the highest BHR were found in the positive control mice (immunized and provoked with a mixture of pollen and TPM), followed by mice immunized with pollen and fraction 2 (which contains organic acids). Fraction 2 also induced the highest number of eosinophils and increased levels of interleukin 5 (IL-5) in the BAL fluid. The highest levels of IL-5, in BAL fluid and sera, were obtained in mice immunized with fraction 6 (moderately polar compounds), a somewhat surprising result since those mice did not produce any IgE, did not have any eosinophils in their BAL, or showed almost no BHR. Our data demonstrate that fractions 2 (organic acids) and 7 (highly polar compounds) seem to contain potential adjuvants stimulating the IL-5 production, the IgE synthesis, the eosinophil recruitment, and the bronchial hyperreactivity. Further characterization at the molecular level is now necessary to be able to identify the exact nature of those potential adjuvants. This will be of help in the future to improve the quality of the urban air aerosol.

Interference of a short-term exposure to nitrogen dioxide with allergic airways responses to allergenic challenges in BALB/c mice

Nitrogen dioxide (NO(2)) is a common indoor and outdoor air pollutant whose role in the induction of asthma is unclear. We investigated the effects of NO(2) on the development of asthma-like responses to allergenic challenge in BALB/c mice. Ovalbumin (OVA)-immunized mice were intranasally challenged with OVA or saline solution just before starting a 3 h exposure to 5 or 20 ppm NO(2) or air. Twenty parts per million of NO(2) induced a significant increase of bronchopulmonary hyperreactivity in OVA-challenged mice and of permeability according to the fibronectin content of the bronchoalveolar lavage fluid (BALF) 24 h after exposure, as compared with air or 5 ppm NO(2). Eosinophilia (cell counts in the BALF and eosinophil peroxidase of lung tissue) was detected at 24 and 72 h with similar levels for air and 20 ppm NO(2), whereas a marked reduction was unexpectedly observed for 5 ppm NO(2). At 24 h, interleukin-5 in the BALF was markedly reduced at 5 ppm compared with 20 ppm NO(2) and was also more intense for 20 ppm NO(2) than for the air group. In contrast to specific IgG1 titers, anti-OVA IgE titers and interleukin-4 in the BALF were not affected by NO(2) exposure. Irrespective of the concentration of NO(2), OVA-challenged mice did not develop late mucosal metaplasia compared with those exposed to OVA-air. These results indicate that a short exposure to NO(2) can exacerbate or inhibit some features of the development of allergic disease in mice and may depend on the concentration of pollutant.

Effects of birch pollen and traffic particulate matter on Th2 cytokines, immunoglobulin E levels and bronchial hyper-responsiveness in mice

BACKGROUND

Health effects due to air pollution arising from motor vehicles are a major public and political concern world-wide. Epidemiological studies have shown that the manifestations of asthma are increased by air pollution in already affected individuals.

OBJECTIVE

To investigate the potential role of air-polluted tunnel dust (traffic particulate matter, TPM) or pure carbon core particles in the initiation and persistence of experimental allergic inflammation.

METHODS

BP2 mice were immunized with birch pollen alone (group B) or pollen together with TPM (group A), or with birch pollen and Al(OH)3 (group C), or with birch pollen and carbon core particles (group D). Before methacholine challenge they were challenged intranasally and thereafter bronchial hyper-reactivity (BHR) was evaluated in a whole-body plethysmograph. Levels of Th2 cytokines, fibronectin and lactate dehydrogenase (LDH) were determined, and differential counts were performed in the bronchoalveolar lavage (BAL) fluid. Sera were collected for determination of antibody titres and cytokine levels.

RESULTS

Specific IgE titres, BHR, the number of recruited eosinophils and levels of fibronectin and LDH in BAL were increased in mice immunized and challenged with a mixture of birch pollen and TPM. However, mice immunized with birch pollen alone and challenged intranasally with pollen or a mixture of pollen and TPM demonstrated the highest levels of IL-4 and IL-5.

CONCLUSION

This study highlights the importance of the exposure to a combination of particulate matters and pollen allergens, in the induction of allergic disease in the airways, and we have demonstrated that polluted tunnel dust has an effect on both the inflammatory and immunological components of experimental allergy. Immunization and challenge with carbon core particles together with birch pollen increased neither the BHR nor the specific IgE production significantly. Our results therefore strongly suggest that it is most likely to be the organic phase bound to the carbon core of the diesel exhaust particles that might have an important adjuvant effect in the induction of experimental allergy.

Fas deficiency delays the resolution of airway hyperresponsiveness after allergen sensitization and challenge

BACKGROUND

In asthma, persistent inflammation might be the result of (1) an impaired ability to clear inflammatory cells from the airways and/or (2) impaired apoptotic responses.

OBJECTIVE

In a mouse model, we investigated the regulatory role of Fas (CD95)-induced apoptosis in the development and resolution of airway inflammation and airway hyperresponsiveness (AHR).

METHODS

Mice that were either Fas-sufficient (wild-type; WT) or Fas-deficient (lpr ) were sensitized by intraperitoneal injections of ovalbumin (OVA) and challenged once intranasally with OVA (IP-IN mice). Control (IN) mice were challenged only.

RESULTS

IP-IN WT mice developed AHR at 48 hours; changes in airway resistance resolved by 96 hours. Airway responsiveness at 48 hours in IP-IN lpr mice was similar to that in IP-IN WT mice. However, in contrast to WT mice, IP-IN lpr mice sustained significant AHR at 96 hours in comparison with IN lpr mice; the AHR resolved by 6 days. Bronchoalveolar lavage fluid cell composition was similar in all of the different groups at 48 hours and 96 hours. Both IP-IN WT mice and lpr mice exhibited similar tissue eosinophilia, whereas IP-IN lpr mice had significantly lower numbers of TdT-mediated dUTP nick end labeling (TUNEL)-positive cells in comparison with IP-IN WT mice at 48 hours. Anti-IL-5 antibody given to IP-IN lpr mice 48 hours and 72 hours after the challenge significantly decreased AHR and eosinophilic inflammation and increased TUNEL-positive cell numbers at 96 hours.

CONCLUSION

These results suggest that Fas expression can regulate the onset and resolution of AHR through an increase in eosinophil apoptosis.

Understanding the pathogenesis of allergic asthma using mouse models

OBJECTIVE

This paper reviews the current views of the pathogenesis of airway eosinophilic inflammation and airway hyperresponsiveness (AHR) in allergic asthma based on mouse models of the disease. The reader will also encounter new treatment strategies that have arisen as this knowledge is applied in practice.

DATA SOURCES

MEDLINE searches were conducted with key words asthma, mouse model, and murine. Additional articles were identified from references in articles and book chapters.

STUDY SELECTION

Original research papers and review articles from peer-reviewed journals were chosen.

RESULTS

Although the mouse model does not replicate human asthma exactly, the lessons learned about the pathogenesis of allergic airway inflammation and AHR are generally applicable in humans. Type 2 T helper lymphocytes (Th2) orchestrate the inflammation and are crucial for the development of AHR. Cells and molecules involved in T cell activation (dendritic cells, T cell receptor, major histocompatibility complex molecule, and costimulatory molecules) are also vital. Besides these, no other cell or molecule could be shown to be indispensable for the establishment of the model under all experimental conditions. There are at least three pathways that lead to AHR. One is dependent on immunoglobulin E and mast cells, one on eosinophils and interleukin-5 (IL-5), and one on IL-13. Eosinophils are probably the most important effector cells of AHR. Radical methods to treat asthma have been tested in the animal model, including modifying the polarity of lymphocyte response and antagonizing IL-5.

CONCLUSIONS

AHR, the hallmark of asthma, is attributable to airway inflammation ultimately mediated by helper T cells via three pathways, at least. The mouse model is also a valuable testing ground for new therapies of asthma.

Preclinical efficacy and safety of mepolizumab (SB-240563), a humanized monoclonal antibody to IL-5, in cynomolgus monkeys

BACKGROUND

Allergic respiratory diseases are characterized by large numbers of eosinophils and their reactive products in airways and blood; these are believed to be involved in progressive airway damage and remodeling. IL-5 is the principal cytokine for eosinophil maturation, differentiation, and survival. Mepolizumab (SB-240563), a humanized monoclonal antibody (mAb) specific for human IL-5, is currently in clinical trials for treatment of asthma.

OBJECTIVE

The purpose of this study was to characterize the pharmacologic activity and long-term safety profile of an anti--human IL-5 mAb to support clinical trials in asthmatic patients.

METHODS

Naive and Ascaris suum -sensitive cynomolgus monkeys received various dose levels of mepolizumab and were monitored for acute and chronic pharmacologic and toxic responses.

RESULTS

To support preclinical safety assessment, cynomolgus monkey IL-5 was cloned, expressed, and characterized. Although monkey IL-5 differs from human IL-5 by 2 amino acids (Ala27Gly and Asn40His), mepolizumab has comparable inhibitory activity against both monkey IL-5 and human IL-5. In A suum--sensitive monkeys, single doses of mepolizumab significantly reduced blood eosinophilia, eosinophil migration into lung airways, and levels of RANTES and IL-6 in lungs for 6 weeks. However, mepolizumab did not affect acute bronchoconstrictive responses to inhaled A suum. In an IL-2--induced eosinophilia model (up to 50% blood eosinophilia), 0.5 mg/kg mepolizumab blocked eosinophilia by >80%. Single-dose and chronic (6 monthly doses) intravenous and subcutaneous toxicity studies in naive monkeys found no target organ toxicity or immunotoxicity up to 300 mg/kg. Monkeys did not generate anti-human IgG antibodies. Monthly mepolizumab doses greater than 5 mg/kg caused an 80% to 100% decrease in blood and bronchoalveolar lavage eosinophils lasting 2 months after dosing, and there was no effect on eosinophil precursors in bone marrow after 6 months of treatment. Eosinophil decreases correlated with mepolizumab plasma concentrations (half-life = 13 days).

CONCLUSION

These studies demonstrate that chronic antagonism of IL-5 by mepolizumab in monkeys is safe and has the potential, through long-term reductions in circulating and tissue-resident eosinophils, to be beneficial therapy for chronic inflammatory respiratory diseases.

IL-5 deficiency abolishes aspects of airway remodelling in a murine model of lung inflammation

BACKGROUND AND OBJECTIVES

Lung remodelling is a recognized feature of chronic asthma. In the present study, we have used IL-5-deficient mice to evaluate the role of this cytokine and eosinophilic inflammation in the initial stages of the structural changes occurring in the lung after antigen challenge.

METHODS

Ovalbumin-sensitized wild type and IL-5-deficient mice were daily challenged for 5 consecutive days and killed 3 or 7 days after the last challenge to study the inflammatory and remodelling events, respectively.

RESULTS

Wild type mice challenged with ovalbumin exhibited an accumulation of eosinophils in the bronchoalveolar lavage (BAL) fluid, associated with a production of BAL cellular fibronectin. Histological analysis also revealed an antigen-specific increase in epithelial and alveolar cell proliferation together with an increase in mucus producing epithelial cells. Eosinophilic infiltration and the associated lung remodelling were totally abrogated in IL-5-deficient mice. In wild type mice, treated intranasally with 1 microg of murine IL-5 for 5 consecutive days, no BAL eosinophilia and structural changes of the lungs could be observed.

CONCLUSION

Our results demonstrate that eosinophil accumulation, but not IL-5 alone, plays a central role in the initial stages of the lung remodelling process and suggests that therapies directed at inhibiting eosinophilic inflammation may be beneficial in treating chronic asthma.

Role of dendritic cells and Th2 lymphocytes in asthma: lessons from eosinophilic airway inflammation in the mouse

Asthma is a chronic disorder of the airways characterized by variable airway narrowing, mucus hypersecretion, and infiltration of the airway wall with eosinophils. It is now believed that asthma is controlled by Th2 lymphocytes producing cytokines such as IL-4, IL-5, IL-9, and IL-13. Animal models of eosinophilic airway inflammation and airway hyperreactivity have been developed to study the contribution of cells or mediators in the pathogenesis of asthma. In this review, we discuss the role of antigen presenting cells, CD4(+) and CD8(+) T lymphocytes, B lymphocytes, NK cells, and mast cells in the induction and maintenance of eosinophilic airway inflammation, mucus hypersecretion, and airway hyperreactivity.

Bronchial interleukin-5 and eotaxin expression in nasal polyposis. Relationship with (a)symptomatic bronchial hyperresponsiveness

An eosinophilic bronchial inflammation was previously demonstrated in patients with nasal polyposis (NP) and asymptomatic bronchial hyperresponsiveness (BHR) similar to that observed in asthmatic patients with NP, whereas patients with NP without BHR did not. The aim of the study was to investigate the contribution of interleukin 5 (IL-5) and eotaxin to the pathogenesis of BHR associated with NP. Eleven patients with NP without BHR (Group A), 8 patients with NP and asymptomatic BHR (Group B), and 9 patients with NP and asthma (Group C) were included. Bronchial biopsies were studied for IL-5 and eotaxin immunoreactivity and IL-5 mRNA expression. IL-5 levels were determined in bronchial lavage (BL). Compared with Groups A and B, Group C patients exhibited higher numbers of IL-5 protein(+) cells, IL-5 mRNA(+) cells, and eotaxin(+) cells in bronchial submucosa. Compared with Group A, Group B patients showed an increased number of IL-5 protein(+) cells, whereas the number of IL-5 mRNA(+) cells and eotaxin(+) cells was similar. IL-5 levels in BL were increased only in Group C. Our study provides evidence of IL-5 involvement in bronchial eosinophilia and in the pathogenesis of asymptomatic BHR associated with NP, whereas both IL-5 and eotaxin are involved in asthma associated with NP.

Temporal association between airway hyperresponsiveness and airway eosinophilia in ovalbumin-sensitized mice

The temporal association between airway inflammation and airway hyperresponsiveness (AHR) has been analyzed in BALB/c mice sensitized to, and subsequently exposed to, a single intranasal challenge of ovalbumin (OVA). In OVA-sensitized/challenged animals only a small increase in responsiveness to methacholine (MCh) was seen at 8 h, peaked at 24 to 48 h, and resolved by 96 h. An early bronchoalveolar lavage fluid (BALF) neutrophil infiltrate (peaking at 8 h postchallenge; approximately 72% total cells was observed) that returned to baseline by 48 h. BALF eosinophil numbers did not increase until 48 h (approximately 32% of total cells), peaked at 96 h (approximately 38% total cells), and remained elevated at 8 d (approximately 27% total cells). Airway tissue eosinophilia preceded changes in BALF. Eosinophil peroxidase (EPO) levels in BALF were elevated in OVA-sensitized/challenged mice at 48 h only. BALF TNF-alpha levels peaked at 8 h, whereas IL-5 and IL-4 levels peaked at 24 h. IL-13 levels were increased at both 24 and 48 h. Mucus-positive cells were not observed in the airway epithelium until 48 h. Administration of IL-5 or VLA-4 antibody prior to OVA challenge prevented the development of AHR in sensitized mice as well as BALF and tissue eosinophilia. These data identify a temporal association between Th2 cytokine production, tissue eosinophil infiltration and activation, and, importantly, both the development and resolution kinetics of AHR. Moreover, the antibody studies further support the association of eosinophilia with the pathogenesis of AHR.

Infection of mice with the helminth Strongyloides stercoralis suppresses pulmonary allergic responses to ovalbumin

Asthma and helminth infections induce similar immune responses characterized by the presence of peripheral blood eosinophilia and elevated serum IgE levels. Epidemiological surveys have reported either increases or decreases in the development of atopic diseases and asthma based on the prevalence of helminth infections in the population. The aim of this study was to determine if a pre-existing helminth infection would increase or decrease subsequent allergic responses to an unrelated allergen in the lungs. BALB/cByJ mice were infected with the nematode parasite Strongyloides stercoralis prior to ovalbumin (OVA) immunization and intratracheal challenge. Bronchoalveolar lavage (BAL) and fluid (BALF) were collected 3 days post-challenge and cellular and humoral immune responses were measured. Intracellular cytokine staining revealed increased IL-4 and IL-5 producing cells in BAL from mice infected with S. stercoralis before OVA sensitization. Increased IL-5 protein levels and decreased IFN-gamma protein levels were also observed in the BALF. There was, however, no increase in airway eosinophil accumulation in mice infectd with parasites before sensitization with OVA as compared to mice exposed to OVA alone. Furthermore, eotaxin levels in the lungs induced by OVA was suppressed in mice infected with the parasite before OVA sensitization. The development of OVA specific IgE responses in BALF was also impaired in mice infected with the parasite before sensitization with OVA. These results suggest that a pre-existing helminth infection may potentiate a systemic Type 2-type response yet simultaneously suppress in the lungs allergen-specific IgE responses and eotaxin levels in response to subsequent exposure to allergens.

Pathogenic roles of eosinophils in guinea-pig contact sensitivity: regulation of dermal eosinophilia with remotely administered IL-5

Eosinophils have a variety of functions. Although increasing evidence links the presence of eosinophils to airway damage, studies have not examined in detail if, and how, eosinophils affect skin inflammation. The purpose of this study was to determine whether eosinophil infiltration augments the contact sensitivity reaction in vivo. Guinea-pigs were sensitized with 2, 4-dinitrochlorobenzene and challenged on the dorsal skin or on the right ear lobe. The number of eosinophils and macroscopic changes of the skin lesion in the presence or absence of human recombinant IL-5 (rIL-5) administered at the remote site was assessed. The reaction on the dorsal skin was acutely eczematous with considerable basophil infiltration. In contrast, eosinophils had extensively infiltrated the right ear lobe and major basic protein was deposited in the dermis. A subcutaneous injection of rIL-5 (10 pmol/kg) at the remote site (left ear lobe) 12 h after challenge induced transient blood eosinophilia and enhanced eosinophil accumulation in the challenged ear lobe. These changes were accompanied by increased ear swelling and severe erythema. In contrast, eosinophil infiltration was significantly inhibited by rIL-5 administered at the time of challenge. Ear thickness, as well as the erythema and oedema, were also reduced. These data suggest that marked eosinophil infiltration enhances skin inflammation in allergic contact dermatitis. Moreover, locally administered IL-5 functions remotely by controlling eosinophil recruitment into the skin. The guinea-pig model of contact sensitivity may be useful for evaluating therapies and pharmaceuticals targeted at eosinophil infiltration.

Cyclooxygenase inhibition increases interleukin 5 and interleukin 13 production and airway hyperresponsiveness in allergic mice

The immunomodulatory role of arachidonic acid metabolites in allergic sensitization is undefined. Prostaglandin E(2) (PGE(2)), a product of arachidonic acid metabolism through the cyclooxygenase pathway, has been reported to favor Type 2-like cytokine secretion profiles in murine and human CD4(+) T cells by inhibiting the production of Type 1-associated cytokines. On the basis of these in vitro data, we hypothesized that indomethacin, a nonselective cyclooxygenase inhibitor, would diminish allergen-induced production of Type 2 cytokines in mice, and protect against airway hyperresponsiveness (AHR) to methacholine. We found that ovalbumin-sensitized mice that were treated with indomethacin (OVA-indomethacin mice) had significantly greater AHR (p < 0.05) and higher levels of IL-5 (176 +/- 52 versus 66 +/- 4 pg/ml) and IL-13 (1,226 +/- 279 versus 475 +/- 65 pg/ml) in lung supernatants than mice sensitized with ovalbumin alone (OVA mice), while levels of IL-4 and serum IgE were not different. Lung mRNA expression of the C-C chemokine MCP-1 was increased in OVA-indomethacin mice, while there was no difference between the two groups in lung mRNA expression of eotaxin, MIP-1alpha, MIP-1beta, or MIP-2. Histologic examination revealed greater pulmonary interstitial eosinophilia in OVA-indomethacin mice as well. Contrary to our expectations, we conclude that in the BALB/c mouse, cyclooxygenase inhibition during allergen sensitization increases AHR, production of IL-5 and IL-13, and interstitial eosinophilia.

Regulation of cyclophosphamide-induced eosinophilia in contact sensitivity: functional roles of interleukin-5-producing CD4(+) lymphocytes

Blood and tissue eosinophilia is obtained when mice pretreated with cyclophosphamide (CY) and sensitized with picryl chloride are challenged on each ear lobe on day 13. To gain important insights into the cellular mechanisms involved in CY-induced eosinophilia in the contact-sensitivity reaction, we examined the cytokine profile expressed in regional lymph node cells and spleen cells. CY pretreatment 2 days before sensitization enhanced expression of IL-4 mRNA in the regional lymph node cells more strongly than expressions of both IL-2 and IFN-gamma mRNA on day 13. Five days after sensitization, spleen cells expressed IL-5 mRNA and produced IL-5 in vitro. Depletion of CD4(+) cells from spleen cells completely abrogated the secretory capacity of IL-5. In vivo blocking of IL-5 on day 3 entirely inhibited spleen, bone marrow, and subsequent blood eosinophilia. When immune lymph node cells prepared on day 13 were stimulated with hapten-modified cells in vitro, the level of IL-4 secreted in the culture supernatant was enhanced by CY pretreatment, but that of IL-2 was not. One important result was that IL-5 was not produced in response to in vitro stimulation, despite the fact that marked eosinophil infiltration in the dermis was observed in vivo. Thus, eosinophilopoiesis was stimulated by IL-5-producing CD4(+) immune T cells that were present in the eosinophil production site, particularly in the spleen before elicitation. In contrast, eosinophil recruitment into the dermis in the efferent phase can be induced without production of IL-5 from lymphocytes.

Airway inflammation driven by antigen-specific resident lung CD4(+) T cells in alphabeta-T cell receptor transgenic mice

CD4(+) T cells are thought to play a major role in the initiation and perpetuation of T helper cell, type 2 (Th2)-like allergic airway inflammation. However, it is not clear whether activation of resident antigen-specific CD4(+) T cells is in itself sufficient to induce such a phenotype. Using ovalbumin (OVA)-specific alphabeta-T cell receptor transgenic Balb/c DO11.10 mice, we were able to test this hypothesis. Nonsensitized DO11.10 mice but not wild-type mice responded to a primary OVA aerosol with a rapid and impressive bronchoalveolar lavage (BAL) neutrophilia followed by a smaller but significant eosinophilia. Responses in DO11.10 mice were mediated by OVA-specific activation of CD4(+) T cells because in vivo depletion of CD4(+) but not CD8(+) T cells abrogated inflammatory cell influx. Cytokines measured in BAL fluid (BALF) after OVA aerosol exposure of DO11.10 mice were indicative of a T helper cell, type 1 (Th1)-like immune response. Further, neutralization of interferon gamma (IFN-gamma) with antibody enhanced eosinophil influx, suggesting that IFN-gamma production was limiting the development of a Th2 response. Despite this, an increased prevalence of cells staining for mucus was seen in the bronchial epithelium, a feature more commonly associated with a Th2-immune response. Unlike what was seen in OVA-sensitized wild-type mice, multiple OVA aerosol exposures of DO11.10 mice failed to induce airway hyperresponsiveness (AHR) to inhaled methacholine. In conclusion, in vivo stimulation of resident lung CD4(+) T cells with antigen caused lung inflammation with characteristics of both a Th1- and Th2-immune response but was insufficient to directly induce AHR.

Anti-interleukin 5 but not anti-IgE prevents airway inflammation and airway hyperresponsiveness

The role of IL-5 and allergen-specific IgE in the development of eosinophilic airway inflammation and airway hyperresponsiveness (AHR) was investigated in a murine model. BALB/c mice were sensitized to ovalbumin (OVA) by intraperitoneal injection on Days 1 and 14, followed by airway challenge with OVA on Days 28 and 29. Anti-IL-5 (TRFK-5) or anti-IgE (antibody 1-5) was administered before each airway challenge. Sensitized and challenged mice developed increased OVA-specific IgE serum levels, Th2 cytokine production by peribronchial lymph node (PBLN) cells, increased numbers of eosinophils (predominantly located in the peribronchial regions of the lungs), and increased airway responsiveness to methacholine (MCh). Anti-IgE treatment significantly decreased serum anti-OVA IgE levels and prevented the development of anaphylaxis but failed to affect T cell function, eosinophil airway infiltration, and AHR in sensitized and challenged mice. In contrast, treatment with anti-IL-5 antibody did not affect B cell (Ig serum levels), T cell (cytokine production), or mast cell function (immediate cutaneous reactivity) but completely inhibited development of eosinophilic lung inflammation and AHR. These data identify IL-5-mediated eosinophilia as a major target for development of AHR in this model, with little effect resulting from neutralization of IgE.

Biology of IL-5 in health and disease

LEARNING OBJECTIVES

Reading this article will increase the readers' knowledge of the biology of interleukin-5 (IL-5), an important cytokine. The immune and inflammatory responses of any organism are the basis of the defense mechanism ensuring its survival. The role of IL-5 in these processes, as well as in the pathogenesis of various diseases has been discussed along with the effects of various pharmacologic agents on the production and function of IL-5.

DATA SOURCES

A detailed literature search was performed. Studies considered relevant and important, in all languages, which involved humans and animals were used.

STUDY SELECTION

Information was obtained only from peer reviewed journals.

RESULTS

Interleukin-5 is normally produced by T-cells, mast cells, and eosinophils while Reed Sternberg and Epstein Barr virus (EBV) transformed cells also produce IL-5. Monoclonal antibodies (mAb) to IL-5 are potent inhibitors of IL-5 mediated tissue damage, secondary to eosinophil infiltration. The majority of the studies on IL-5 are preliminary, often the information is obtained from animal studies or in vitro systems and occasionally from pathologic tissue analysis. This along with the absence of confirmatory studies is a limiting factor. Nonetheless, the role of IL-5 in allergic and immunologic disease and asthma may be central to their pathogenesis.

CONCLUSIONS

Interleukin-5 is an important molecule that is participant to many processes that maintain health and are involved directly or indirectly in the pathogenesis of disease. Some pharmacologic agents can modify IL-5 production in vivo. Development of selective inhibitors of IL-5 may have a potential use for specific therapy of certain autoimmune, inflammatory, and neoplastic diseases.

Airway exposure to bacterial superantigen (SEB) induces lymphocyte-dependent airway inflammation associated with increased airway responsiveness--a model for non-allergic asthma

Although immunological consequences of systemic superantigen administration have been extensively studied, the effects of local mucosal exposure to superantigens are not well defined. The purpose of this study was to delineate the type of immune response triggered by superantigen exposure to the airway mucosa in mice. In dose-response experiments we determined a low dose of staphylococcal enterotoxin B (SEB) that triggered an inflammatory response characterized by mucosal and airway recruitment of lymphocytes, eosinophils and neutrophils together with elevated levels of IL-4, but not IFN-gamma, in bronchoalveolar lavage (BAL) fluids. TCR Vbeta analysis revealed that superantigen-responsive and -non-responsive T cells were equally recruited into the airways. SEB markedly enhanced the frequency of TNF-alpha-positive BAL macrophages as well as the amount of TNF-alpha in BAL fluids. These responses were associated with the development of increased airway responsiveness (AR) in SEB-treated mice. This effect occurred in an antibody-independent fashion. Furthermore, this type of response was observed in IgE-high responder BALB/c as well as in IgE-low/intermediate responder C57BL/6 mice. The development of increased AR was CD4+ T cell dependent as shown by transfer experiments into BALB/c nu/nu mice. These results suggest that the local immune response following mucosal superantigen administration triggers a unique inflammatory response in the airways resembling many features of "intrinsic asthma".

Prevention of Th2-Like Cell Responses by Coadministration of IL-12 and IL-18 Is Associated with Inhibition of Antigen-Induced Airway Hyperresponsiveness, Eosinophilia, and Serum IgE Levels

Allergic asthma is thought to be regulated by Th2 cells, and inhibiting this reponse is a promising mode of intervention. Many studies have focused on differentiation of Th cells to the Th1 or Th2 subset in vitro. IL-4 is essential for Th2 development, while IL-12 induces Th1 development, which can be enhanced by IL-18. In the present study, we investigated whether IL-12 and IL-18 were able to interfere in Th2 development and the associated airway symptoms in a mouse model of allergic asthma. Mice were sensitized with OVA using a protocol that induces IgE production. Repeated challenges by OVA inhalation induced elevated serum levels of IgE, airway hyperresponsiveness, and a predominantly eosinophilic infiltrate in the bronchoalveolar lavage concomitant with the appearance of Ag-specific Th2-like cells in lung tissue and lung-draining lymph nodes. Whereas treatments with neither IL-12 nor IL-18 during the challenge period were effective, combined treatment of IL-12 and IL-18 inhibited Ag-specific Th2-like cell development. This inhibition was associated with an absence of IgE up-regulation, airway hyperresponsiveness, and cellular infiltration in the lavage. These data show that, in vivo, the synergistic action of IL-12 and IL-18 is necessary to prevent Th2-like cell differentiation, and consequently inhibits the development of airway symptoms in a mouse model of allergic asthma.

Circulating, but not local lung, IL-5 is required for the development of antigen-induced airways eosinophilia

IL-5 is induced locally in the lung and systemically in the circulation during allergic airways eosinophilic inflammation both in humans and experimental animals. However, the precise role of local and systemic IL-5 in the development of allergic airways eosinophilia remains to be elucidated. In our current study, we demonstrate that compared with their IL-5(+/+) counterparts, IL-5(-/-) mice lacked an IL-5 response both in the lung and peripheral blood, yet they released similar amounts of IL-4, eotaxin, and MIP-1alpha in the lung after ovalbumin (OVA) sensitization and challenge. At cellular levels, these mice failed to develop peripheral blood and airways eosinophilia while the responses of lymphocytes, neutrophils, and macrophages remained similar to those in IL-5(+/+) mice. To dissect the relative role of local and systemic IL-5 in this model, we constructed a gene transfer vector expressing murine IL-5. Intramuscular IL-5 gene transfer to OVA-sensitized IL-5(-/-) mice led to raised levels of IL-5 compartmentalized to the circulation and completely reconstituted airways eosinophilia upon OVA challenge, which was associated with reconstitution of eosinophilia in the bone marrow and peripheral blood. Significant airways eosinophilia was observed for at least 7 d in these mice. In contrast, intranasal IL-5 gene transfer, when rendered to give rise to a significant but compartmentalized level of transgene protein IL-5 in the lung, was unable to reconstitute airways eosinophilia in OVA-sensitized IL-5(-/-) mice upon OVA-challenge, which was associated with a lack of eosinophilic responses in bone marrow and peripheral blood. Our findings thus provide unequivocal evidence that circulating but not local lung IL-5 is critically required for the development of allergic airways eosinophilia. These findings also provide the rationale for developing strategies to target circulating IL-5 and/or its receptors in bone marrow to effectively control asthmatic airways eosinophilia.

IL-5 and IL-5 receptor in asthma

Eosinophils, along with mast cells are key cells involved in the innate immune response against parasitic infection whereas the adaptive immune response is largely dependent on lymphocytes. In chronic parasitic disease and in chronic allergic disease, IL-5 is predominantly a T cell derived cytokine which is particularly important for the terminal differentiation, activation and survival of committed eosinophil precursors. The human IL-5 gene is located on chromosome 5 in a gene cluster that contains the evolutionary related IL-4 family of cytokine genes. The human IL-5 receptor complex is a heterodimer consisting of a unique alpha subunit (predominantly expressed on eosinophils) and a beta subunit which is shared between the receptors for IL-3 & GM-CSF (more widely expressed). The alpha subunit is required for ligand-specific binding whereas association with the beta subunit results in increased binding affinity. The alternative splicing of the alpha IL-5R gene which contains 14 exons can yield several alpha-IL-5R isoforms including a membrane-anchored isoform (alpha IL-5Rm) and a soluble isoform (alpha IL-5Rs). Cytokines such as IL-5 produce specific and non-specific cellular responses through specific cell membrane receptor mediated activation of intracellular signal transduction pathways which, to a large part, regulate gene expression. The major intracellular signal transduction mechanism is activation of non-receptor associated tyrosine kinases including JAK and MAP kinases which can then transduce signals via a novel family of transcriptional factors named signal transducers and activators of transcription (STATS). JAK2, STAT1, and STAT5 appear to be particularly important in IL-5 mediated eosinophil responses. Asthma is characterized by episodic airways obstruction, increased bronchial responsiveness, and airway inflammation. Several studies have shown an association between the number of activated T cells and eosinophils in the airways and abnormalities in FEV1, airway reactivity and clinical severity in asthma. It has now been well documented that IL-5 is highly expressed in the bronchial mucosa of atopic and intrinsic asthmatics and that the increased IL-5 mRNA present in airway tissues is predominantly T cell derived. Immunocytochemical staining of bronchial biopsy sections has confirmed that IL-5 mRNA transcripts are translated into protein in asthmatic subjects. Furthermore, the number of activated CD4 + T cells and IL-5 mRNA positive cells are increased in asthmatic airways following antigen challenge and studies that have examined IL-5 expression in asthmatic subjects before and after steroids have shown significantly decreased expression following oral corticosteroid treatment in steroid-sensitive asthma but not in steroid resistant and chronic severe steroid dependent asthma. The link between T cell derived IL-5 and eosinophil activation in asthmatic airways is further strengthened by the demonstration that there is an increased number of alpha IL-5R mRNA positive cells in the bronchial biopsies of atopic and non-atopic asthmatic subjects and that the eosinophil is the predominant site of this increased alpha IL-5R mRNA expression. We have also shown that the subset of activated eosinophils that expressed mRNA for membrane bound alpha IL-5r inversely correlated with FEV1, whereas the subset of activated eosinophils that expressed mRNA for soluble alpha IL-5r directly correlated with FEV1. Hence, not only does this data suggest that the presence of eosinophils expressing alpha IL-5R mRNA contribute towards the pathogenesis of bronchial asthma, but also that the eosinophil phenotype with respect to alpha IL-5R isoform expression is of central importance. Finally, there are several animal, and more recently in vitro lung explant, models of allergen induced eosinophilia, late airway responses (LARS), and bronchial hyperresponsiveness (BHR)--all of which support a link between IL-5 and airway eosinophilia and bronc

Allergen challenge-induced extravasation of plasma in mouse airways

BACKGROUND

Mouse models are extensively used to study genetic and immunological mechanisms of potential importance to inflammatory airway diseases, e.g. asthma. However, the airway pathophysiology in allergic mice has received less attention. For example, plasma extravasation and the ensuing tissue-deposition of plasma proteins, which is a hallmark of inflammation, has not been examined in allergic mice.

OBJECTIVE

This study aims to examine the vascular permeability and the distribution of plasma proteins in mouse airways following exposure to allergen and serotonin.

METHODS

Extravasated plasma was quantified by a dual isotop technique using intravascular (131I-albumin) and extrasvascular (125I-albumin) plasma tracers. Histological visualization of fibrinogen and colloidal gold revealed the tissue distribution of extravasated plasma.

RESULTS

Allergen aerosol exposure (3% OVA, 15min) of sensitized animals resulted in a marked plasma extravasation response in the trachea (P < 0.01) and the bronchi but not in the lung parenchyma. A similar extravasation response was induced by serotonin (P<0.001). Extravasating vessels (assessed by Monastral blue dye) were identified as intercartilaginous venules. Extravasated plasma abounded in the subepithelial tissue but was absent in the epithelium and airway lumen. The allergen-induced response was dose-dependently inhibited by iv administration of formoterol (P < 0.001), a vascular antipermeability agent.

CONCLUSION

The present study demonstrates that serotonin and allergen challenge of sensitized mice increase airway venular permeability to cause transient extravasation and lamina propria distribution of plasma in the large airways. We suggest that the extravasation response is a useful measure of the intensity and the distribution of active inflammation

Various immunological phenotypes are associated with increased airway responsiveness

BACKGROUND

Bronchial asthma is characterized by a TH2 type immune response, chronic inflammation of the airways and increased airway responsiveness. The relationship between IgE- and inflammatory-dependent mechanisms that contribute to bronchial asthma are not well defined.

OBJECTIVE

The purpose of this study was to compare and analyse the immune pathways that resulted in development of allergen-induced and/or inflammatory dependent increased airways responsiveness.

RESULTS

BALB/c and C57BL/6 mice responded to OVA-sensitization with elevated allergen-specific IgE/IgG1 serum antibody-titres and the development of cutaneous immediate-type hypersensitivity reactions. Increased airway responsiveness was observed following airway allergen challenges. However, the inflammatory component of the lung differed between the strains. In OVA-sensitized BALB/c mice a marked increase in lymphocytes, eosinophils and neutrophils in BAL fluids was parallelled with elevated production of IL-4, IL-5 and TNFalpha in the lung. In contrast in OVA-sensitized C57BL/6 mice, the inflammatory immune response in the lung was much weaker. We postulate that two pathways can regulate the induction of increased airway responsiveness. One depends on the presence of allergen-specific IgE/IgG1 and allergen, and a second is mediated by allergen-independent inflammation of the lung. To test this hypothesis, BALB/c mice were treated nasally with low doses of bacterial superantigen (SEB) as a prototypical inducer of airway inflammation, following which influx of lymphocytes, eosinophils and neutrophils into the airways was parallelled by development of increased airway-responsiveness in the absence of allergen-specific IgE/IgG1 antibodies and allergen.

CONCLUSIONS

These results indicate that increased airway responsiveness is associated with different immunological phenotypes in BALB/c and C57BL/6 mice.

Airway hyperresponsiveness: first eosinophils and then neuropeptides

Airway hyperreactivity to bronchoconstrictor mediators is a main characteristic in the majority of asthmatic patients and correlates well with the severity of the disease. The airways of asthmatic patients are characterized by an inflammatory state resulting in activation of lung tissue cells and attraction and infiltration of leukocytes from the blood. The accumulation of eosinophilic leukocytes is a prominent feature of inflammatory reactions that occurs in allergic asthma. The increase in number of eosinophils is important since it correlates in time with an increase in bronchial hyperresponsiveness. Viral respiratory infections can also induce eosinophilia and airway hyperresponsiveness in humans and animals and can worsen asthmatic reactions. This report reviews current opinions on the relationship between inflammation-induced eosinophil accumulation/activation and the development of airway hyperresponsiveness and the possible role for sensory neuropeptides in this process. Firstly, CC chemokines play an important role in allergic airway inflammation and respiratory viral infections leading to eosinophil recruitment. Secondly, it can be concluded that IL5 is involved in the development in airway hyperresponsiveness. IL5 has profound effects on eosinophils as promoter of growth, differentiation and proliferation, chemoattractant, activator and primer. However, it is conceivable that in animal models for allergic asthma besides IL5 other regulatory mediators may be involved in eosinophil migration and activation in the lung, which in turn will lead to airway hyperresponsiveness. Recent data support the possible role of eotaxin and its eosinophil-specific receptor CCR-3 in eosinophil chemotaxis and activation in allergic asthma. Moreover, it is suggested that the development of airway eosinophilia in vivo involves a two-step mechanism, elicited by eotaxin and IL5. The precise mechanism by which eosinophils induce bronchial hyperresponsiveness is at present unknown. Sensory neuropeptides could be important mediators in this process, since it has been demonstrated that airway nerves are surrounded by and infiltrated with eosinophils after antigen challenge. Sensory neuropeptides could be the final, more downstream, common pathway after eosinophil infiltration and activation in inducing airway hyperresponsiveness due to allergen inhalation or respiratory viral infections. In conclusion, in the process of the development of airway hyperresponsiveness observed during viral infections or in allergic asthma, the IL5/eotaxin-induced infiltration and activation of eosinophils in the airways is evident. Following this step, eosinophil-derived inflammatory mediators will induce the release of sensory neuropeptides (possibly NK2-receptor activating tachykinins) which in turn will lead to airway hyperresponsiveness.

Role for neurokinin-2 receptor in interleukin-5-induced airway hyperresponsiveness but not eosinophilia in guinea pigs

In the guinea pig, interleukin-5 (IL-5) has been shown to induce airway hyperresponsiveness as well as eosinophilia, which are important symptoms in asthma. IL-5 seems to be a critical cytokine since it selectively affects eosinophil functions. The mechanism of action by which IL-5 leads to airway hyperresponsiveness may be important for our understanding of the pathogenesis of asthma. Neurogenic inflammation, which is mediated by nonadrenergic noncholinergic nerves (NANC), may play a role in the IL-5-induced effects in guinea pig airways. In this study, the role of neuropeptides in the IL-5-induced airway hyperresponsiveness and eosinophilia in the guinea pig was examined using selective neurokinin receptor antagonists. Intra-airway application of IL-5 (1 microgram, twice) induces a selective eosinophil migration (control: 12 [8-22] x 10(5) cells and IL-5: 90 [67-187] x 10(5) cells, p < 0.05) and activation (control: 6.3 +/- 0.9 ng eosinophil peroxidase [EPO]/ml bronchoalveolar lavage [BAL] fluid and IL-5: 29.3 +/- 4.9 ng EPO/ml BAL fluid, p < 0.05) and a pronounced airway hyperresponsiveness in vivo. The maximal responses to histamine are increased by 160 +/- 16% (p < 0.05) after IL-5. Treatment of guinea pigs with either the nonselective neurokinin (NK)-receptor antagonist, FK224, or the selective NK2-receptor antagonist, SR48968, results in a complete inhibition of the in vivo hyperresponsiveness found after application of IL-5. Vice versa, intra-airway administration of substance P (10 micrograms, twice) results in an airway hyperresponsiveness (increased maximal response after substance P: 166 +/- 15% [p < 0.05]) without inducing migration or activation of eosinophils. All examined NK-receptor antagonists do not influence the IL-5-induced eosinophil accumulation. In addition, no effect of the NK-receptor antagonists is observed on the IL-5-induced eosinophil activation, as determined by BAL fluid EPO levels. The release of NK2-receptor active tachykinins plays an important role in the development of IL-5-induced airway hyperresponsiveness. This feature appears to be a step following eosinophil infiltration and activation since there are no effects on eosinophil function by pretreatment of the used NK-receptor antagonists.

Cyclophosphamide-induced blood and tissue eosinophilia in contact sensitivity: mechanism of hapten-induced eosinophil recruitment into the skin

The mechanism leading to selective production and accumulation of eosinophils in certain allergic skin diseases is unknown. Cyclophosphamide treatment (150 mg/kg) of BALB/c mice 48 h before sensitization with picryl chloride (PCl) resulted in striking blood and tissue eosinophilia, maximal at 13 days. Blood eosinophilia was not induced by the sensitization with oxazolone and 2,4-dinitrofluorobenzene. Challenge with 1 % PCl, but not croton oil caused preferential eosinophil accumulation into the dermis, which was associated with the enhanced expression of vascular cell adhesion molecule 1 (VCAM-1) on endothelial cells. Intravenous administration of anti-VCAM-1 monoclonal antibody abrogated eosinophil infiltration. In this murine model, we examined the role of several cytokines, including chemokines in inducing selective tissue eosinophilia in vivo. Local administration of antibodies against interleukin (IL)-1beta, IL-4, tumor necrosis factor (TNF)-alpha, and RANTES, but not against IL-5 before challenge inhibited hapten-induced eosinophil recruitment. Intradermal injection of recombinant (r)IL-1beta, rIL-4, rTNF-alpha, rRANTES, and rMIP-1alpha induced marked eosinophil accumulation. Nonetheless, intradermal rIL-5 was not a chemoattractant for eosinophils in vivo. Our findings suggest that IL-1beta, IL-4, TNF-alpha, and RANTES contribute to the selective accumulation of eosinophils in contact sensitivity reaction. Although circulating IL-5 can activate eosinophils and prolong their survival, locally secreted IL-5 is not crucial for inducing eosinophil recruitment into the skin.

Blockade of CD28/B7 co-stimulation by mCTLA4-Hgamma1 inhibits antigen-induced lung eosinophilia but not Th2 cell development or recruitment in the lung

We have studied the role of the CD28/B7 co-stimulatory pathway in the development of a Th2-type lung immune response. Mice injected two or three times intraperitoneally with ovalbumin in alum adjuvant and then re-exposed to the same antigen by intranasal (i.n.) inoculation show infiltration of the lung tissue and appearance in the broncho-alveolar lavage (BAL) fluid of significant numbers of eosinophils and lymphocytes, in a pattern which is reminiscent of asthmatic inflammation. The accumulation of eosinophils in the airways is completely dependent on interleukin (IL)-5 secretion by CD4+ T cells. We have used mice transgenic for a soluble form of murine CTLA-4 (mCTLA4-Hgamma1) which binds to B7 molecules on antigen-presenting cells, thereby preventing their interaction with T cell-expressed CD28. mCTLA4-Hgamma1-transgenic mice immunized intraperitoneally and challenged i.n. with ovalbumin failed to generate any eosinophil infiltration, suggesting that little or no IL-5 was secreted in the lungs of these mice. In contrast with the complete lack of eosinophils, the numbers and phenotypes of infiltrating lymphocytes were comparable in the lungs of mCTLA4-Hgamma1-transgenic and normal mice. Also, lung lymphocytes from immunized mCTLA4-Hgamma1-transgenic and normal mice could be shown to secrete comparable amounts of IL-4 and IL-5 when stimulated in culture in the absence of mCTLA4-Hgamma1. We conclude that mCTLA4-Hgamma1 can efficiently block the production of IL-5 during in vivo responses and inhibit eosinophil recruitment, but that it does not block the development of CD4+ T cells into Th2 cells with the potential to secrete IL-5.

The relevance of murine animal models to study the development of allergic bronchial asthma

Bronchial asthma (BA) develops on the basis of a genetic predisposition and involves a characteristic sequence of changes in immune functions. In the immunopathogenesis, several phases can be distinguished: the initial stage is defined as the development of allergic sensitization. This step is dependent on: (i) T cell activation; (ii) IL-4 production; (ii) IgE synthesis; and (iv) mediator release by effector cells. The second phase of allergic inflammation as a consequence of the T cell dependent sensitization is characterized by IL-5 production and eosinophil activation and recruitment. Airway mucosa remodelling is the consequence of chronic inflammatory processes and represents the final stage of BA. In this article animal models will be discussed with regard to their relevance for these different phases in development of chronic allergic BA.