The appearance of hypodense eosinophils in antigen-dependent late phase asthma

Eosinophilic inflammation: An Appealing Target for Pharmacologic Treatments in Severe Asthma

Severe asthma is characterized by different endotypes driven by complex pathologic mechanisms. In most patients with both allergic and non-allergic asthma, predominant eosinophilic airway inflammation is present. Given the central role of eosinophilic inflammation in the pathophysiology of most cases of severe asthma and considering that severe eosinophilic asthmatic patients respond partially or poorly to corticosteroids, in recent years, research has focused on the development of targeted anti-eosinophil biological therapies; this review will focus on the unique and particular biology of the eosinophil, as well as on the current knowledge about the pathobiology of eosinophilic inflammation in asthmatic airways. Finally, current and prospective anti-eosinophil therapeutic strategies will be discussed, examining the reason why eosinophilic inflammation represents an appealing target for the pharmacological treatment of patients with severe asthma.

Eosinophil diversity in asthma

Eosinophils are a type of granulated innate immune cells that have long been implicated in a specific type of asthma, referred to as eosinophilic asthma. Several immunotherapeutics that target and deplete eosinophils or limit their numbers are currently widely used and provide improved disease outcome in severe eosinophilic asthma. Current clinical results provide conclusive evidence of a generally detrimental role of eosinophils in asthma. Yet, a small but growing body of reports suggests that eosinophils may be more diverse than currently appreciated. In this review, we explore pre-clinical and clinical evidence that suggests the existence of eosinophil subsets with potentially distinct functional roles in asthma. We conclude by discussing state-of-the-art strategies for deciphering heterogeneity of this complex cell type, and argue this knowledge could translate into the improved personalized treatment of severe eosinophilic asthma.

Diagnosis and management of eosinophilic asthma: a US perspective

Eosinophilic asthma is now recognized as an important subphenotype of asthma based on the pattern of inflammatory cellular infiltrate in the airway. Eosinophilic asthma can be associated with increased asthma severity, atopy, late-onset disease, and steroid refractoriness. Induced sputum cell count is the gold standard for identifying eosinophilic inflammation in asthma although several noninvasive biomarkers, including fractional exhaled nitric oxide and periostin, are emerging as potential surrogates. As novel therapies and biologic agents become increasingly available, there is an increased need for specific phenotype-directed treatment strategies. Greater recognition and understanding of the unique immunopathology of this asthma phenotype has important implications for management of the disease and the potential to improve patient outcomes. The present review provides a summary of the clinical features, pathogenesis, diagnosis, and management of eosinophilic asthma.

Asthma outcomes: biomarkers

BACKGROUND

Measurement of biomarkers has been incorporated within clinical research studies of asthma to characterize the population and associate the disease with environmental and therapeutic effects.

OBJECTIVE

National Institutes of Health institutes and federal agencies convened an expert group to propose which biomarkers should be assessed as standardized asthma outcomes in future clinical research studies.

METHODS

We conducted a comprehensive search of the literature to identify studies that developed and/or tested asthma biomarkers. We identified biomarkers relevant to the underlying disease process progression and response to treatment. We classified the biomarkers as either core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an National Institutes of Health-organized workshop convened in March 2010 and finalized in September 2011.

RESULTS

Ten measures were identified; only 1, multiallergen screening to define atopy, is recommended as a core asthma outcome. Complete blood counts to measure total eosinophils, fractional exhaled nitric oxide (Feno), sputum eosinophils, urinary leukotrienes, and total and allergen-specific IgE are recommended as supplemental measures. Measurement of sputum polymorphonuclear leukocytes and other analytes, cortisol measures, airway imaging, breath markers, and system-wide studies (eg, genomics, proteomics) are considered as emerging outcome measures.

CONCLUSION

The working group participants propose the use of multiallergen screening in all asthma clinical trials to characterize study populations with respect to atopic status. Blood, sputum, and urine specimens should be stored in biobanks, and standard procedures should be developed to harmonize sample collection for clinical trial biorepositories.

Update on clinical and immunological features of eosinophilic gastrointestinal diseases

PURPOSE OF REVIEW

Eosinophilic gastrointestinal diseases (EGIDs) are an increasingly common heterogeneous group of intestinal diseases. The purpose of this review is to present the latest developments in the care of patients with EGIDs and to summarize a growing literature defining the clinical features and mechanistic elements of eosinophils and their complex relationships with the gastrointestinal tract.

RECENT FINDINGS

Recent studies continue to define what constitutes 'normal' and 'abnormal' numbers of eosinophils in the different sections of the gastrointestinal tract. Symptom complexes of EGIDs appear to be related primarily to the mucosal, as opposed to the muscular or serosal, forms of EGIDs. Dissection of the mucosal microenvironment is uncovering a complex array of cells, other than eosinophils, that likely contribute to the inflammatory response associated with EGIDs. Mechanistic studies have identified genetic perturbations (eotaxin-3, thymic stromal lymphopoietin, IL-13, and filaggrin) that may also contribute to the development of the most often encountered and well studied EGID, eosinophilic esophagitis.

SUMMARY

Clinicians should remain aware of EGIDs as a diagnostic possibility for patients with common gastrointestinal symptoms. Additional research is needed to determine mechanistic processes leading to dysfunction associated with eosinophilic gastrointestinal inflammation.

Tryptase as an inflammatory marker in allergic disease and asthma

Asthma is a chronic inflammatory disease of the airways, varying from occasional episodes of wheezing and shortness of breath, to an irreversible, life-threatening obstructive disease. While many cases are managed with relative ease, others do not respond to the traditional inhaled therapy or even to oral glucocorticosteroids. Although it cannot be cured as yet, asthma can be controlled if properly diagnosed. Usually, functional clinical parameters form the basis for estimation of the disease severity. In addition, the growing database of cytokine and mediator profiles have allowed their exploitation as molecular markers for processes underlying airway inflammation in asthma. Tryptase is a potent and versatile mediator in allergic inflammation, orchestrating both acute and chronic events by acting on a vast array of cells and tissue components. For more than a decade, tryptase has been used as a marker for allergic inflammation in asthma as well as in a variety of other airway diseases. In this review, the current advantages and disadvantages of the use of tryptase as an inflammatory marker in asthma will be discussed.

Dendritic cells in allergic airway inflammation

Dendritic cells (DCs) are primary antigen-presenting cells involved in interactions with T cells leading to the proliferation of TH1 or TH2 cell types. In asthma, predominance of TH2 cells appears to be responsible for disease pathogenesis. Differentiation of TH2 cells is driven by a variety of factors such as the expression of high levels of costimulatory molecules, the cytokine profile, and the subset of DCs. Many inflammatory cells involved in the pathogenesis of asthma either directly or indirectly modulate DC function. Traditional treatments for asthma decrease the number of airway DCs in animals as well as in patients with asthma. Immunomodulators including interleukin (IL)-10, transforming growth factor (TGF)-beta, cytosine-phosphate-guanosine-containing oligodeoxynucleotides (CpG-ODN), 1alpha,25-dihydroxyvitamin D3, and fetal liver tyrosine kinase 3 ligand (Flt3L) are involved in the modulation of the function of DCs. Based on the critical review of the interaction between DCs and other inflammatory cells, we propose that activation of T cells by DCs and sensitization to inhaled allergen and resulting airway inflammation are dependent on plasmacytoid and myeloid subset of lung DCs to induce an immune response or tolerance and are tightly regulated by T-regulatory cells. Effects of various therapeutic agents to modulate the function of lung myeloid DCs have been discussed.

[Activated eosinophils: techniques to characterize them]

The deleterious role thought to be played by eosinophils in many situations is linked to their ability to secrete various inflammatory substances, mainly toxic proteins and lipid mediators, in body tissue. This ability is a particular feature of activated eosinophils, which have undergone numerous metabolic, functional, and phenotypic changes from their resting state. Characterizing the properties of these activated cells is an essential step in improving our understanding of their contributions to local inflammatory response, as both regulatory and effector cells. Improvements in existing methods as well as the development of new technical approaches have facilitated the ex vivo and in vitro study of activated eosinophils and their contribution to various disease states.

Eosinophils alter colonic epithelial barrier function: role for major basic protein

Mucosal eosinophils increase in a number of gastrointestinal diseases that are often associated with altered epithelial barrier function, including food allergic enteropathies and inflammatory bowel diseases. Although eosinophils are known to secrete biologically active mediators including granule proteins, their role in gastrointestinal diseases is uncertain. The aim of this study was to determine the impact of eosinophils on intestinal barrier function. Epithelial barrier function was determined in a coculture of eosinophils and T84 epithelial cells and in a murine model of T helper (Th) type 2-mediated colitis. Coculture conditions resulted in decreased transepithelial resistance (TER) and increased transepithelial flux. Cell-free coculture supernatants contained a > or =5-kDa soluble factor that also diminished TER; these supernatants contained the eosinophil-granule proteins major basic protein (MBP) and eosinophil-derived neurotoxin (EDN). T84 barrier function decreased significantly when basolateral surfaces were exposed to native human MBP but not EDN. Additional studies identified downregulation of the tight junctional molecule occludin as at least one mechanism for MBP action. MBP-null mice were protected from inflammation associated with oxazolone colitis compared with wild-type mice. In conclusion, MBP decreases epithelial barrier function and in this manner contributes to the pathogenesis of inflammatory bowel diseases.

Leukocyte oxidant and antioxidant status in asthmatic patients

BACKGROUND

Oxidative stress mediated by reactive oxygen species (ROS) is recognized to contribute significantly to the inflammatory process of bronchial asthma (BA). These species are released into the airway by activated inflammatory cells such as leukocytes. In this study, we aimed to determine whether the oxidant-antioxidant balance is changed in leukocytes of patients with BA.

METHODS

Thirty eight patients (21 male, 17 female) aged 22-68 years and controls of 32 subjects (18 male, 14 female) aged 20-63 years were included in the study. A total of 10 mL venous blood was drawn, leukocytes were separated and lipid peroxidation (LPO), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and vitamin C levels were determined in both patients and controls.

RESULTS

Leukocyte LPO and SOD activity in the patient group were higher than that of controls (p <0.001 and p <0.05, respectively). However, leukocyte GSH-Px and vitamin C levels in the patient group were lower than that of controls (p <0.01 and p <0.001, respectively).

CONCLUSIONS

The results suggest that there are alterations in a wide array of oxidants and antioxidants with balance shifting toward increased oxidative stress in BA.

Altered pituitary-adrenal interaction in nocturnal asthma

BACKGROUND

Increased airway inflammation at night contributes to the nocturnal worsening of asthma, but the mechanisms regulating circadian variations in airway inflammation are unknown.

OBJECTIVE

We hypothesized that altered hypothalamic-pituitary-adrenal axis function serves as an endogenous controller of inflammation in nocturnal asthma.

METHODS

Patients with nocturnal asthma (n = 7), patients with nonnocturnal asthma (n = 13), and healthy control subjects (n = 11) adhered to a regular sleep-wake cycle for 1 week. Corticotropin and cortisol levels were assayed every 2 hours for 24 hours. Low-dose corticotropin stimulation was performed. Circadian hormonal flux was analyzed by means of cosinor modeling and calculation of the area under the 24-hour curve.

RESULTS

Corticotropin peak levels and areas under the 24-hour curve were significantly increased in patients with nocturnal asthma versus values in patients with nonnocturnal asthma and control subjects. Patients with nonnocturnal asthma demonstrated significantly increased areas under the 24-hour cortisol curve when compared with control subjects, but peak cortisol levels did not differ between groups. Cortisol levels after low-dose corticotropin stimulation did not differ between groups. Corticotropin and cortisol levels were not correlated with the degree of physiologic impairment.

CONCLUSION

Nocturnal asthma is marked by increased corticotropin levels that are not accompanied by commensurate increases in cortisol levels. This observation might indicate blunted adrenal responsiveness in the nocturnal asthma phenotype. Conversely, adrenal response to corticotropin might be enhanced in nonnocturnal asthma, attenuating nocturnal worsening of airway inflammation.

Transcriptional regulation of the IL-5 gene in peripheral T cells of asthmatic patients

Mechanisms that underlie the regulation of IL-5 gene expression in human peripheral T cells remain incompletely defined because of the low efficiency of transfection of plasmid constructs into non-transformed T cells. To elucidate the cellular and molecular mechanisms of IL-5 production, concanavalin A (ConA)-stimulated blastocytes derived from peripheral blood lymphocytes of asthmatic patients were employed in this study. Transcriptional activity of the synthetic human IL-5 promoter in ConA-stimulated blastocytes correlated with the production of IL-5. Deletion analysis of the reporter gene showed that the cis-regulatory element located at - 119 to - 80 is critical for inducible IL-5 promoter activity. Electrophoretic mobility shift assay revealed that an oligonucleotide probe corresponding to the element (- 119 to - 90) gave two specific bands. The slower migrating band was absolutely dependent on stimulation and was composed of a co-operative complex of the transcription factors, nuclear factor of activated T cells (NFAT) and activating protein-1 (AP-1). The faster migrating band was also inducible and was identified as AP-1-less NFAT. Mutation of either the NFAT or AP-1 element abrogated the slower migrating band and at the same time abolished transcriptional activity of the human IL-5 promoter/enhancer gene. Cyclosporin A equivalently suppressed DNA-binding activity of the composite NFAT/AP-1 site, promoter activity and protein production of IL-5. In conclusion, these data suggests that the composite NFAT/AP-1 binding element (- 115 to - 100) plays a crucial role in IL-5 synthesis by peripheral T cells of asthmatic patients.

Immunomodulatory effects of melatonin in asthma

Patients with nocturnal asthma demonstrate circadian variations in airway inflammation. We hypothesized that melatonin, a circadian rhythm regulator, modulates circadian inflammatory variations in asthma. The effect of melatonin stimulation on peripheral blood mononuclear cell cytokine production was evaluated at 4:00 P.M. and 4:00 A.M. in normal control subjects, patients with nocturnal asthma, and patients with non-nocturnal asthma. Melatonin was proinflammatory, causing significantly increased production of interleukin-1, interleukin-6, and tumor necrosis factor-alpha at 4:00 P.M. and 4:00 A.M. in all subject groups (range, 12.8 +/- 3.3 to 131.72 +/- 16.4%, p < or = 0.0003). The observed increases in cytokine production did not change between 4:00 P.M. and 4:00 A.M. in control subjects or in patients with nocturnal asthma (p > 0.05, both cases). At 4:00 P.M., the cytokine response to melatonin of patients with nocturnal asthma was greater than that of control subjects or patients with non-nocturnal asthma and did not change significantly at 4:00 A.M. At 4:00 P.M., the cytokine response of patients with non-nocturnal asthma was less than that of patients with nocturnal asthma and rose significantly at 4:00 A.M. (p = 0.0001, all comparisons). Melatonin is proinflammatory in both patients with asthma and healthy subjects. Patients with nocturnal asthma demonstrate the largest daytime cytokine response and cannot be further stimulated at 4:00 A.M., suggesting chronic overstimulation in vivo. These results suggest differential immunomodulatory effects of melatonin based on asthma clinical phenotype and may indicate an adverse effect of exogenous melatonin in asthma.

The association between persistent eosinophilia and asthma in childhood is independent of atopic status

BACKGROUND

Although peripheral blood eosinophilia is associated with risk of asthma, the relation with atopy has not been established.

OBJECTIVE

To assess the relationship between eosinophils and chronic asthma in childhood, and to determine the factors associated with eosinophil levels over time.

METHODS

Percent eosinophils/300 white blood cell (WBC) count ('eos') was measured at 9 months, 6 years and 11 years in subjects participating in the prospective Tucson Children's Respiratory Study. Children were classified based on the number of measurements in which they had low (< or = 2%) or high (>5%) eosinophils, as follows: (1) Persistently low eos (n = 130); (2) Low eos (intermittently low or consistently moderate, but never high, n = 317); (3) Intermittently high eos (n = 192); and (4) Persistently high eos (n = 17). Only children with > or = 2 eos measurements were included in the analysis. Chronic asthma was defined as medical doctor (MD)-diagnosed asthma with reports of wheezing during the previous year, on > or = 3 questionnaires completed between 2 and 13 years of age. Children with at least one positive skin prick test (SPT; > or = 3 mm) at age 6 or 11 were considered 'atopic'.

RESULTS

Chronic asthma was linearly related to longitudinally ascertained eosinophils (trend chi2 P<0.001) with prevalence ranging from 5.8% among children with persistently low eos to 37.5% among children with persistently high eos. This relation was independent of atopy. Parental history of asthma was associated with both chronic asthma (P <0.001) and with longitudinal eosinophil status (P < 0.001). After adjusting for atopy and gender, there was a 70% increase in asthma risk with each increase in longitudinal eosinophil level. This stepwise increase was reduced to 48% when parental asthma was added to the model.

CONCLUSION

Longitudinal eosinophil levels are linearly associated with chronic asthma in childhood, independent of atopy. The strong association between parental asthma and eosinophil status suggests that genetic background may be an important determinant of eosinophilic response.

Correlation between eosinophilia induced by CD4(+) T cells and bronchial hyper-responsiveness

The relationship between CD4(+) T cell-mediated airway eosinophilic inflammation and bronchial hyper-responsiveness (BHR) was investigated. Ovalbumin-reactive T(h)0 clones were adoptively transferred to unprimed BALB/c mice and then the mice were challenged by inhalation of the relevant antigen. Upon antigen provocation, infused T(h) clones infiltrated into the airways, followed by the accumulation and degranulation of eosinophils, goblet cell hyperplasia, edema and increase in bronchial responsiveness to acetylcholine. Transfer of several clones that differed in the levels of IL-5 production revealed that the magnitude of in vivo eosinophilia strongly correlated with the IL-5-producing capacity of the infused T(h) clones. Administration of anti-IL-5 mAb almost completely suppressed antigen-induced eosinophilic inflammation and BHR. Administration of anti-IL-4 mAb or anti-IFN-gamma mAb enhanced the eosinophilia and BHR, whereas anti-IL-2 mAb did not affect them. The number of accumulated eosinophils significantly correlated with the intensity of BHR. Our present results clearly demonstrated that CD4(+) T cells induced BHR as a result of eosinophilic inflammation. IL-5 totally regulated both responses.

Systemic activation of basophils and eosinophils: markers and consequences

Basophils and eosinophils are important effector cells in human allergic diseases; they play a significant role in promoting allergic inflammation through the release of proinflammatory mediators (such as histamine, leukotriene C(4), major basic protein, eosinophil cationic protein, IL-4, and IL-13, among others). Notably, in allergic subjects, these cells exist in higher numbers and in a more activated state compared with nonatopic control subjects. Evidence for the greater activation state includes increased expression of intracellular and surface markers and hyperreleasability of allergy mediators. We have been interested in the phenotypic markers of effector-cell activation for many years. There is considerable overlap among activation markers, and few activation markers have been found that define a unique phenotype that is quantifiable in the assessment of the presence and severity of allergic disease. This review summarizes the existing evidence for systemic activation of human basophils and eosinophils in allergic diseases. The potential mechanisms responsible for functional and morphologic alterations in these effector cells and the specificity and utility of surface markers in the assessment of allergic disease activity or severity are also discussed.

Attenuation of the allergen-induced late asthmatic reaction by cyclosporin A is associated with inhibition of bronchial eosinophils, interleukin-5, granulocyte macrophage colony-stimulating factor, and eotaxin

The allergen-induced late asthmatic reaction (LAR) is associated with increases in bronchial eosinophils and basophils as well as upregulation of several eosinophil active cytokines and C-C chemokines. Cyclosporin A (CsA) was previously shown to inhibit the LAR, but not the early asthmatic reaction (EAR), and this was associated with a decrease in blood eosinophils. For these reasons, we determined whether CsA inhibited the allergen-induced increases in bronchial eosinophils, basophils, eotaxin, interleukin-5 (IL-5), and granulocyte macrophage colony-stimulating factor (GM-CSF). Subjects with a demonstrable LAR underwent bronchoscopy with biopsy and bronchoalveolar lavage (BAL) at baseline and then were randomly allocated to receive either CsA (n = 13) or placebo (n = 11) before challenge. A second bronchoscopy was performed 24 h later. The LAR, but not the EAR, was significantly attenuated in the CsA group compared with placebo (p < 0.05). CsA significantly inhibited the allergen-induced increases in IL-5 (p = 0.02) and GM-CSF (p = 0. 0028) in mRNA+ cells in BAL, and in a mAB against human activated eosinophils (EG2+) (p = 0.0227). We conclude that inhibition of the LAR by CsA may be related to its inhibitory effects on eosinophil-associated cytokines and chemokines. The beneficial effect of CsA in asthma may also be the result of inhibition of eosinophil accumulation.

Inhibition of allergic inflammation in a murine model of asthma by expression of a dominant-negative mutant of GATA-3

The cytokines IL-4, IL-5, and IL-13, secreted by Th2 cells, have distinct functions in the pathogenesis of asthma. We have previously shown that the transcription factor GATA-3 is expressed in Th2 but not Th1 cells. However, it was unclear whether GATA-3 controls the expression of all Th2 cytokines. Expression of a dominant-negative mutant of GATA-3 in mice in a T cell-specific fashion led to a reduction in the levels of all the Th2 cytokines IL-4, IL-5, and IL-13. Airway eosinophilia, mucus production, and IgE synthesis, all key features of asthma, were severely attenuated in the transgenic mice. Thus, targeting GATA-3 activity alone is sufficient to blunt Th2 responses in vivo, thereby establishing GATA-3 as a potential therapeutic target in the treatment of asthma and allergic diseases.

Biologic rhythms in the immune system

In all of its components, the immune system shows regularly recurring, rhythmic variations in numerous frequencies; the circadian (about 24 h) rhythms are the best explored. The circadian variations in immunocompetent cells circulating in the peripheral blood are of a magnitude to require attention in medical diagnostics. Both the humoral arm and the delayed (cellular) arm of the immune system function in a rhythmic manner. The response of the immune system to introduction of an antigen and to challenge of the sensitized organism varies in extent in the circadian frequency range and also in lower frequencies, for example, of about a week (circaseptan) or seasonally (circannual). The medical application of the biologic rhythms of the immune system extends to diagnostic measures, as well as treatment.

Essential role of nuclear factor kappaB in the induction of eosinophilia in allergic airway inflammation

The molecular mechanisms that contribute to an eosinophil-rich airway inflammation in asthma are unclear. A predominantly T helper 2 (Th2)-type cell response has been documented in allergic asthma. Here we show that mice deficient in the p50 subunit of nuclear factor (NF)- kappaB are incapable of mounting eosinophilic airway inflammation compared with wild-type mice. This deficiency was not due to a block in T cell priming or proliferation in the p50(-/-) mice, nor was it due to a defect in the expression of the cell adhesion molecules VCAM-1 and ICAM-1 that are required for the extravasation of eosinophils into the airways. The major defects in the p50(-/-) mice were the lack of production of the Th2 cytokine interleukin 5 and the chemokine eotaxin, which are crucial for proliferation and for differentiation and recruitment, respectively, of eosinophils into the asthmatic airway. Additionally, the p50(-/-) mice were deficient in the production of the chemokines macrophage inflammatory protein (MIP)-1alpha and MIP-1beta that have been implicated in T cell recruitment to sites of inflammation. These results demonstrate a crucial role for NF-kappaB in vivo in the expression of important molecules that have been implicated in the pathogenesis of asthma.

Interleukin-4 and interleukin-5 as targets for the inhibition of eosinophilic inflammation and allergic airways hyperreactivity

Clinical and experimental investigations suggest that allergen-specific CD4+ T-cells, IgE and the cytokines IL-4 and IL-5 play central roles in initiating and sustaining an asthmatic response by regulating the recruitment and/or activation of airways mast cells and eosinophils. IL-5 plays a unique role in eosinophil development and activation and has been strongly implicated in the aetiology of asthma. The present paper summarizes our recent investigations on the role of these cytokines using cytokine knockout mice and a mouse aeroallergen model. Investigations in IL-5-/-mice indicate that this cytokine is critical for regulating aeroallergen-induced eosinophilia, the onset of lung damage and airways hyperreactivity during allergic airways inflammation. While IL-4 and allergen-specific IgE play important roles in the regulation of allergic disease, recent investigations in IL-4-/- mice suggest that allergic airways inflammation can occur via pathways which operate independently of these molecules. Activation of these IL-4 independent pathways are also intimately associated with CD4+ T-cells, IL-5 signal transduction and eosinophilic inflammation. Such IL-5 regulated pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell mediated processes. The central role of IL-5 in both components of allergic disease highlights the requirements for highly specific therapeutic agents which inhibit the production or action of this cytokine.

A Novel T Cell-Regulated Mechanism Modulating Allergen-Induced Airways Hyperreactivity in BALB/c Mice Independently of IL-4 and IL-5

The immunoregulatory functions of IL-4 and IL-5 have identified these cytokines as primary targets for the resolution of airways inflammation and bronchial hyperreactivity in asthma. However, the individual contribution of each of these cytokines and of IL-5-regulated eosinophilia to the induction of airways hyperreactivity in mouse models of asthma remains highly controversial. In this investigation, we have used IL-4- and IL-5-deficient mice of the same genetic background in combination with inhibitory mAbs to these cytokines to identify unequivocally the contribution of these factors to the induction of airways hyperreactivity. Sensitization and aeroallergen challenge of wild-type mice with OVA induced pathological changes to the respiratory epithelium, airways eosinophilia, and hyperreactivity to β-methacholine. Inhibition of the actions of IL-4 and/or IL-5 did not abolish airways hyperreactivity, and in the case of IL-4-deficient mice pretreated with anti-IL-5 mAb, airways hyperreactivity persisted in the absence of pronounced airways inflammation. Airways hyperreactivity was abolished only by anti-CD4+ mAb treatment. However, aeroallergen challenge of IL-5−/− mice showed that morphologic changes to the airways were critically linked to IL-5 and eosinophilia. This investigation demonstrates the existence in BALB/c mice of a novel CD4+ T cell pathway for modulating airways hyperreactivity. These findings may provide an explanation for the dissociation of airways eosinophilia from the development of airways hyperreactivity observed in some cases of asthma and in animal models of this disease.

Evidence that cyclosporin A and dexamethasone inhibit allergic airway eosinophilic inflammation via suppression of interleukin-5 synthesis by T cells

1. We have recently demonstrated that airway eosinophilic inflammation can be transferred to unprimed mice by infusing interleukin (IL)-5-producing T cell clones. Using that murine model, we performed this study to delineate the mechanism of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation. 2. The ovalbumin-reactive murine T cell clones, FJ17, produced IL-2, IL-4 and IL-5 upon stimulation with relevant antigen. In FJ17-transferred mice, messenger RNA (mRNA) of IL-2 and IL-5 expressed in the lungs, the number of eosinophils in bronchoalveolar lavage fluid (BALF) was increased and the bronchial responsiveness to acetylcholine was enhanced after antigen provocation. 3. Cyclosporin A (10, 100 ng ml(-1)) and dexamethasone (10, 100 ng ml(-1) suppressed the production of IL-5 as well as IL-2 and IL-4 by FJ17 in vitro. 4. Subcutaneously administered cyclosporin A (30 mg kg(-1)) and dexamethasone (10 mg kg(-1)) inhibited antigen-induced mRNA expression of IL-2 and IL-5, increase of BALF eosinophils and bronchial hyperresponsiveness of FJ17-transferred mice in vivo. The number of BALF eosinophils was correlated with the bronchial responsiveness to acetylcholine (r=0.672). 5. The results clearly indicated that the suppression of IL-5 synthesis by T cells is involved in the effects of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation.

Granulocyte macrophage colony-stimulating factor augments ICAM-1 and VCAM-1 activation of eosinophil function

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are members of the immunoglobulin superfamily adhesion molecules on vascular endothelium and important in the development of eosinophil (EOS) accumulation in allergic inflammation. To define the role of these adhesion proteins in EOS inflammation, peripheral blood EOS from allergic donors were incubated in either buffer (control)-, recombinant human (rh)-VCAM-1-, or rh-ICAM-1-coated plates, and the effects of these adhesion proteins on EOS effector functions were determined. VCAM-1 induced spontaneous EOS adhesion whereas EOS adhesion to ICAM-1 required a second signal, such as granulocyte macrophage colony-stimulating factor (GM-CSF). Although only VCAM-1 stimulated EOS superoxide anion (O2-) generation, the addition of GM-CSF (100 pM) to the reactions resulted in a greater and equivalent production of O2- with VCAM-1 and ICAM-1. In the presence of GM-CSF, ICAM-1 and VCAM-1 caused significant release of EOS-derived neurotoxin (EDN). Moreover, only ICAM-1 (no GM-CSF) promoted calcium ionophore A23187 (0.2 microM)-induced EOS leukotriene C4 (LTC4). Enhanced O2- generation, EDN release, and LTC4 generation observed with ICAM-1 and VCAM-1 were significantly inhibited by anti-beta2-integrin antibody. These results suggest that ICAM-1 and VCAM-1 are important in determining the eventual function of airway EOS.

Clinical utility of serum levels of eosinophil cationic protein (ECP) for monitoring and predicting clinical course in childhood asthma

BACKGROUND

The concentration of ECP in serum has been proposed as a marker of airway inflammation in asthma. However, its clinical significance is still to be determined.

OBJECTIVES

This study was performed to determine whether concentration of ECP in serum reflects clinical status in asthma and can serve as a predictive parameter.

METHODS

Cross-sectional analysis was performed in 28 children with asthma. A total of 91 blood samples was obtained to determine levels of ECP in serum and eosinophil counts. Forced expiratory volume in 1 s was also determined at the time of the sampling. Data were analysed on the basis of asthma symptoms in the 4 weeks before and the 4 weeks after sampling.

RESULTS

Serum levels of ECP were significantly lower in patients who had been asymptomatic for 3 or 4 weeks before sampling than in patients who had been symptomatic or asymptomatic for only 1 or 2 weeks. In the former group, serum levels of ECP were higher when patients became symptomatic after sampling than when they remained stable, a finding that suggests that serum levels of ECP may have a predictive value in certain situations. Although the concentration of ECP in serum was not proved to be predictive in the latter symptomatic group, the concentration of ECP was significantly lower when measured again 4 weeks later when the patients' symptoms had resolved. In contrast, levels of ECP were unchanged when patients remained symptomatic, a finding that suggests serum levels of ECP may reflect the clinical response to therapy.

CONCLUSIONS

Serum ECP may be a useful marker for monitoring and predicting the clinical course in asthma.

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.

Transcription factor GATA-3 is differentially expressed in murine Th1 and Th2 cells and controls Th2-specific expression of the interleukin-5 gene

Interleukin-5 (IL-5), which is produced by CD4(+) T helper 2 (Th2) cells, but not by Th1 cells, plays a key role in the development of eosinophilia in asthma. Despite increasing evidence that the outcome of many diseases is determined by the ratio of the two subsets of CD4(+) T helper cells, Th1 and Th2, the molecular basis for Th1- and Th2-specific gene expression remains to be elucidated. We previously established a critical role for the transcription factor GATA-3 in IL-5 promoter activation in EL-4 cells, which express both Th1- and Th2-type cytokines. Our studies reported here demonstrate that GATA-3 is critical for expression of the IL-5 gene in bona fide Th2 cells. Whereas mutations in the GATA-3 site abolished antigen- or cAMP-stimulated IL-5 promoter activation in Th2 cells, ectopic expression of GATA-3 in Th1 cells or in a non-lymphoid, non-IL-5-producing cell line activated the IL-5 promoter. During the differentiation of naive CD4(+) T cells isolated from T cell receptor transgenic mice, GATA-3 gene expression was up-regulated in developing Th2 cells, but was down-regulated in Th1 cells, and antigen- or cAMP-activated Th2 cells (but not Th1 cells) expressed the GATA-3 protein. Thus, GATA-3 may play an important role in the balance between Th1 and Th2 subsets in immune responses. Inhibition of GATA-3 activity has therapeutic potential in the treatment of asthma and other hypereosinophilic diseases.

Effects of ketotifen on symptoms and on bronchial mucosa in patients with atopic asthma

Ketotifen is marketed throughout the world as an antiallergy drug, but whether it affects infiltration of inflammatory cells into airway mucosa is not known. We studied the effects of ketotifen on symptoms, pulmonary function, and airway inflammation in 25 patients with atopic asthma. Patients took ketotifen (1 mg twice daily) or a matching placebo for 8 weeks in a double-blind, parallel-group study. Data recorded on diary cards were used for 2 weeks before treatment began, and they were used for the last 2 weeks of treatment to study asthma symptoms, use of beta 2-agonists, and peak expiratory flow (PEF). Pulmonary function tests, bronchial responsiveness to methacholine, and fiberoptic bronchoscopy were performed before and after treatment. Biopsy specimens were obtained by bronchoscopy. Specimens were stained immunohistochemically with monoclonal antibodies against stored eosinophil cationic protein (EG1), the secreted form of eosinophil cationic protein (EG2), mast-cell tryptase (AA1), neutrophil elastase (NP57), CD3, CD4, CD8, and CD25. The numbers of positively stained cells in the lamina propria were counted. Compared with the placebo, the ketotifen-treated group exhibited significant improvement of asthma symptoms (P < 0.05) and bronchial responsiveness (P < 0.05). This was accompanied by a reduction of EG2+ eosinophils (P < 0.05), CD3+ T cells (P < 0.001), CD4+ T cells (P < 0.01), and CD25+ activated T cells (P < 0.01) in the bronchial mucosa. These results suggested that the beneficial effects of ketotifen in bronchial asthma may result from consequent inhibition of activated eosinophils and T-cell recruitment into the airway. Moreover, ketotifen may relieve allergic inflammation in bronchial asthma.

Inhibitory effect of cetirizine on cytokine-enhanced in vitro eosinophil survival

BACKGROUND

Cetirizine is an antihistamine that inhibits in vivo eosinophil influx into the inflamed airways following allergen challenge, and in vitro eosinophil chemotaxis and adhesion. Since eosinophils are proposed to have an important role in the pathophysiology of asthma and allergic disease, the effects of cetirizine on eosinophil function may be a mechanism of this agent's therapeutic regulation of the allergic reaction.

OBJECTIVE

To determine the effect of cetirizine on in vitro eosinophil survival.

METHODS

Using human eosinophils isolated from patients with allergic rhinitis, the cells were cultured in vitro for 48 to 72 hours with medium, cetirizine, or dexamethasone in the presence of IL-5, IL-3, or GM-CSF. Eosinophil survival was assessed by trypan blue exclusion.

RESULTS

In the presence of IL-5, but not GM-CSF or IL-3 100 microM cetirizine significantly inhibited eosinophil survival at 48 and 72 hours; the magnitude of this inhibition was dependent on cytokine concentration. Although cetirizine significantly suppressed cytokine promotion of eosinophil survival, it was not as potent as dexamethasone.

CONCLUSIONS

Although the in vitro concentration of cetirizine was required to be quite high, cetirizine may affect in vivo airway inflammation through its inhibition of IL-5-dependent eosinophil survival.

Effect of isolation protocol on eosinophil function: Percoll gradients versus immunomagnetic beads

Studies of in vitro eosinophil function are dependent on efficient and reliable methods of cell isolation. Protocols using Percoll or metrizamide density gradients have been of limited use in isolating peripheral blood eosinophils in sufficient numbers and purity from subjects with normal or only slightly elevated eosinophil counts, thereby restricting comparative studies to preparations from hypereosinophilic subjects. Recently, a method utilizing negative selection by anti-CD16 coated magnetic beads has greatly improved eosinophil isolation by dramatically increased yields and purity. However, little is known as to the differential effect of various isolation methods on the functional activity of eosinophils. In this study, eosinophils were isolated by either discontinuous multiple density Percoll gradients or anti-CD16-coated magnetic beads: several functional activities were then compared using cells obtained by the two methods of isolation. Compared with Percoll isolated eosinophils, anti-CD16 bead separated eosinophils had significantly increased baseline and stimulated LTC4 production, spontaneous O2- generation, and expression of specific cell surface markers. No significant difference was observed in the cells' in vitro survival and adhesion. Such differences may be due to the isolation of eosinophils of all densities by anti-CD16 beads, or the effect of neutrophils interacting with the beads to release eosinophil agonists or primers. Alternatively, the Percoll gradient method with the eosinophils' exposure to dextran and Ficoll-Hypaque may affect subsequent cell function. Therefore, comparison of eosinophil function between cells isolated by different protocols must be considered before concluding which is the true measure of in vivo cell function.

The eosinophil and its role in asthma

1. The eosinophil is part of the host defence mechanism to parasitic infection, but is also a key cell in many inflammatory disorders. 2. Eosinophils synthesise a range of pro-inflammatory and cytotoxic mediators, such as basic proteins, hydrolytic enzymes, lipid mediators, cytokines, oxygen metabolites and neuropeptides. 3. Eosinophils are recruited to the lung during episodes of asthma. They migrate from the blood vessels into the tissue via a series of interactions between their surface adhesion molecules and endothelial cells or the extracellular matrix. 4. Activation and prolonged survival of eosinophils occurs upon exposure to mediators released from other tissue resident leukocytes, including eosinophils themselves, and from respiratory tract epithelial cells. Release of eosinophilic mediators causes tissue damage and persistent inflammation of the lung. 5. Currently the most effective therapy for asthma lies with anti-inflammatory drugs, of which the main choices are inhaled corticosteroids or cromolyn sodium and nedocromil sodium.

Sephadex G-200-induced eosinophil infiltration into airways in non-sensitized and sensitized guinea pigs, and responsiveness of the cells to stimuli in vitro

Eosinophils are thought to be one of the pathophysiologically pivotal cells in atopic-type inflammation. In the present experiments, the in vitro responsiveness to stimuli of eosinophils, which had infiltrated into the airway following intravenous administration of Sephadex G-200 (Sephadex), was mainly studied in non-sensitized and [antigen + Al(OH)3]-sensitized guinea pigs. In sensitized, Sephadex-treated guinea pigs, a large number of eosinophils were found in the bronchoalveolar lavage fluid, whereas a much smaller number of cells were recovered in either non-sensitized or sensitized, Sephadex-untreated animals and a smaller number were recovered in non-sensitized Sephadex-treated animals. The eosinophils from non-sensitized Sephadex-treated guinea pigs released superoxide anion (.O2-) and thromboxane (TX) B2 in response to platelet-activating factor (PAF), leukotriene B4 and Ca ionophore A23187. Either spontaneous or PAF-induced .O2- generation from eosinophils of sensitized, Sephadex-treated guinea pigs was significantly greater than that from non-sensitized animals, while TXB2 release stimulated by any of the above stimuli was not further enhanced by sensitization. These results indicate that active sensitization can change some eosinophil functions and that the functionally altered cells could play a pathophysiological role in atopic inflammation.

Effect of eosinophil peroxidase on airway epithelial permeability in the guinea pig

Increased numbers of eosinophils and increased concentrations of plasma proteins have been found in the airways of patients with mild asthma. We used an intact guinea pig trachea model to investigate the role of eosinophil peroxidase (EPO) in altering the function of the airway epithelial barrier. EPO in the presence of hydrogen peroxide (H(2)O(2)) and bromide (Br(-)) catalyzes the production of hypobromous acid (HOBr), which is felt to have a toxic effect on airway epithelial cells. An intact guinea pig trachea was mounted on an apparatus in a way that would allow the tracheal epithelium to be exposed to different solutions. Following these exposures, a test solution containing (14)C-sucrose (S), (3)H-inulin (I), and FITC-dextran-20 (D) was placed in the tracheal lumen and positioned in the center of the segment for 90 minutes. Flux of these molecules across the epithelial barrier into a bath was measured, and the permeability (P) was calculated for each molecule to quantify epithelial barrier function. Light and electron micrographic studies were performed to assess cellular damage. We found that there was a dose response to EPO (in the presence of fixed amounts of H(2)(O)(2) and Br(-)). EPO at 7.3 x 10(-7) M caused no increase in P over controls (Ringer's solution alone) for S, I, or D (P> 0.05), whereas EPO at 2.7 x 10(-6) M caused a significant increase in P over controls (P = 0.008) for all test molecules. Light and electron micrographs of the latter tracheas showed no evidence of microscopic changes despite the increased P. Further testing verified that the increase in permeability was caused by the EPO catalyzed reaction and not the individual substrates themselves, and that the reaction was inhibited by a peroxidase inhibitor. We conclude that EPO can alter the barrier function of the airway epithelium before gross cellular damage becomes visible. We hypothesize that changes in the tight junctions are responsible for the alteration in the barrier function of the airway epithelium and that this may play an important role in the pathophysiology of mild asthma.

Allergen-induced inflammation in the nose: a comparison of acute and repeated low-dose allergen exposure

To investigate allergic rhinitis induced by two experimental provocation models, we compared local inflammation with markers of eosinophil activity in peripheral blood. Patients with strictly seasonal allergic rhinitis were selected and investigated outside the pollen season. An acute challenge with increasing doses of allergen every 15 min until symptoms occurred was performed in nine patients. Nasal lavage and blood samples were taken before and 4 and 24 h after challenge. After a 6-week washout period, 10 patients were submitted to 7 days of repeated low allergen exposures. One small dose (approximately equal to 1/100 of the acute dose) was given each day. Blood and lavage samples were taken prior to and after the period. As control four patients were challenged with diluent only. The acute challenge resulted in sneezing and nasal discharge and blockage and was accompanied by a rise in histamine and eosinophil cationic protein (ECP) in lavage fluid after 4 h and continuing after 24 h, when there also was a rise in the number of eosinophils and ECP in peripheral blood. The repeated low-dose exposures caused very few symptoms but produced increased ECP in the lavage fluid and a trend toward increased histamine concentration. There were no changes in ECP, intracellular EG2 binding, or number of eosinophils in the blood. No changes were seen in the control group. Our findings show that changes in eosinophil mediator release in nasal lavage can be seen after very low, but repeated, allergen exposures despite no, or minimal, clinical symptoms.

Density of eosinophils reflects activity of disease in allergic asthmatic children

BACKGROUND

Low density eosinophils are more prominent in asthmatic patients compared with healthy subjects. LDE are metabolically more active and produce more tissue-injuring and spasmogenic proteins than normal eosinophils.

OBJECTIVE AND METHODS

With a method providing information about eosinophils of 12 different densities we were able to study eosinophil density characteristics in 24 young patients in detail with allergic asthma in a stable phase, and in 21 patients after a bronchial allergen challenge.

RESULTS

Study of the eosinophil density profile of patients and healthy controls revealed two density populations. Patients had more low density eosinophils than controls. In the patients eosinophil density characteristics and in particular the number of low density eosinophils correlated strongly with both FEV1% predicted (p = -0.66, P < 0.001) and FEV1/FVC (p = -0.47, P < 0.01) as well as with bronchial responsiveness to histamine (p = -0.68, P < 0.001) and house dust mite (p = -0.37, P < 0.05). Allergen induced bronchial reactions were associated with an increase in the number (P < 0.001) and percentage (P < 0.05) of low density eosinophils. A selective rise in the number of eosinophils collected from fractions with a low density accounted for the observed rise in the total number of eosinophils. Density changes did not differ between patients with an isolated early reaction and patients with both an early and a late reaction, nor was there a relation between the severity of the late reaction and the shift in eosinophil density.

CONCLUSION

In conclusion, peripheral blood eosinophil density characteristics and in particular numbers of low density eosinophils are closely related with indicators of the asthma severity under stable conditions. Allergen inhalation induces a further shift towards lower density suggesting additional activation of the eosinophils.

Clinical value of monitoring eosinophil activity in asthma

To evaluate the use of eosinophil cationic protein (ECP) in monitoring disease activity in childhood asthma, serum ECP in 175 asthmatic children was assessed. Forty five patients with cystic fibrosis, 23 with lower respiratory tract infections (LRTI), and 87 healthy children were used as controls. Serum ECP concentrations (34.3 micrograms/l v 9.8 micrograms/l) were significantly higher in children with bronchial asthma than in healthy control subjects. In symptomatic patients with asthma serum ECP concentrations were increased compared with those from asymptomatic patients (40.2 micrograms/l v 14.4 micrograms/l), irrespective of treatment modalities (that is steroids, beta 2 agonists, or sodium cromoglycate). Moreover, atopy and infection appeared to be factors enhancing eosinophil activity in bronchial asthma as measured by serum ECP (58.4 micrograms/l v 36.8 micrograms/l and 68.8 micrograms/l v 42.2 micrograms/l, respectively). In a longitudinal trial, antiasthmatic treatment modalities (that is steroids) reduced serum ECP within four weeks (42.2 micrograms/l v 19.0 micrograms/l). In conclusion, the data indicate that (1) eosinophils also play a central part in childhood asthma; (2) serum concentrations of ECP in children with bronchial asthma are related to the disease severity and may thus be used for monitoring inflammation in childhood asthma; (3) eosinophil activity appears to be enhanced by atopy and infection; and (4) longitudinal measurements of serum ECP concentrations may be useful for optimising anti-inflammatory treatment in children with bronchial asthma.

Comparison of the effects of salmeterol and salbutamol on clinical activity and eosinophil cationic protein serum levels during the pollen season in atopic asthmatics

BACKGROUND

In atopic asthma there is strong evidence of eosinophils playing an active role in pathogenesis. Some investigations demonstrated that eosinophil cationic protein (ECP) serum levels increased in atopic patients with asthma during pollen season.

OBJECTIVE

The aim of the study was to evaluate the effects of short-term (1 week) beta 2-agonist treatment on lung function and eosinophil activity in asthmatic patients.

METHODS

We used an open, randomized, cross-over design to compare the effects of salbutamol (200 micrograms q.i.d.) and salmeterol (50 micrograms b.i.d.) on peak expiratory flow rate (PEFR), blood eosinophil count and serum levels of ECP as a measure of eosinophil activity in 20 mild atopic asthmatics.

RESULTS

Morning and evening PEFR values were both significantly higher during salmeterol treatment than during the salbutamol period. Conversely, both morning and evening daily asthma symptom scores were significantly lower during salmeterol treatment compared with those recorded during the salbutamol period. The mean basal eosinophil blood count on salmeterol treatment (601 +/- 189 mm3) was not higher than the mean count on salbutamol treatment (612 +/- 204 mm3). After both treatments the mean eosinophil blood counts were unchanged (619 +/- 189 mm3 and 576 +/- 212 mm3, respectively). No significant differences in blood eosinophil counts were observed between or within treatments at any time. No significant difference was observed in baseline mean ECP serum concentration (43.8 +/- 26.3 micrograms/L on salmeterol treatment and 41.7 +/- 29.8 micrograms/L on salbutamol treatment, respectively). After salmeterol treatment the mean ECP serum concentration had fallen significantly to 20.9 +/- 18.6 micrograms/L (P < 0.01), whereas after salbutamol treatment it was unchanged (42.0 +/- 25.1 micrograms/L). Salmeterol treatment produced a decrease in ECP serum levels without any changes in blood eosinophil count.

CONCLUSION

This study demonstrates that salmeterol affords a significant improvement in asthma control during the pollen season, measured by both subjective and objective parameters, compared with salbutamol. This greater efficacy may be related to inhibition of eosinophil degranulation during the pollen season.

Transfer of allergic airway responses with antigen-primed CD4+ but not CD8+ T cells in brown Norway rats

Activated CD4+ helper T cells have been demonstrated in asthmatic airways and postulated to play a central role in eliciting allergic inflammation; direct evidence of their involvement seems to be lacking. We hypothesized that CD4+ T cells have the potential to induce allergic responses to antigen challenge, and tested this hypothesis in a model of allergic bronchoconstriction, the Brown Norway rat, using the approach of adoptive transfer. Animals were actively sensitized to either ovalbumin (OVA) or BSA and were used as donors of T cells. W3/25(CD4)+ or OX8(CD8)+ T cells were isolated from the cervical lymph nodes of sensitized donors and transferred to naive BN rats. 2 d after adoptive transfer recipient rats were challenged by OVA inhalation, and changes in lung resistance (RL), bronchoalveolar lavage (BAL) cells, and serum levels of antigen-specific IgE were studied. After OVA challenge recipients of OVA-primed W3/25+ T cells exhibited sustained increases in RL throughout the entire 8-h observation period and had significant bronchoalveolar lavage eosinophilia, which was detected by immunocytochemistry using an antimajor basic protein mAb. Recipients of BSA-primed W3/25+ T cells or OVA-primed OX8+ T cells failed to respond to inhaled OVA. OVA-specific immunoglobulin E was undetectable by ELISA or skin testing in any of the recipient rats after adoptive transfer. In conclusion, antigen-induced airway bronchoconstriction and eosinophilia were successfully transferred by antigen-specific W3/25+ T cells in Brown Norway rats. These responses were dependent on antigen-primed W3/25+ T cells and appeared to be independent of IgE-mediated mast cell activation. This study provides clear evidence for T cell mediated immune mechanisms in allergic airway responses in this experimental model.

Individual time-courses of ECP and EPX during allergen provocation tests in asthmatic children

To study the time-course of eosinophil cationic protein (ECP) and eosinophil protein X (EPX) during bronchial allergen provocation, we investigated 32 asthmatic children sensitive to house-dust mites as well as 6 non-atopic young adult controls. In all subjects, allergen challenges were performed with house dust mite extracts of Dermatophagoides pteronys-sinus or Dermatophagoides farinae. Blood samples were taken at regular intervals during the 24-h observation period. The individual time-courses of ECP and EPX revealed different characteristic groups of patterns: (1) an isolated early serum peak of both mediators during or within the first 60 min after provocation (2) an early plus a late peak (3) an isolated late peak 12 h after provocation (4) an isolated late peak 24 h after provocation, and (5) no significant variation during the 24-h observation period. The early peak could be due to short-term changes in eosinophil activation, while late peaks may reflect eosinophil proliferation, recruitment, subsequent priming and enhancing of the propensity to release their proteins. ECP and EPX showed a corresponding parallel time-course in nearly all challenges, with EPX-concentration exceeding that of ECP. There was no correlation between ECP/EPX serum concentrations and clinical parameters such as lung function data. From our results we conclude that the striking groups of time-courses of ECP/EPX serum concentration indicate different uniform patterns of eosinophil activation during allergen challenge-but do not predict clinical outcome of provocation. The role of the eosinophil in early asthmatic reactions remains to be established in further studies.

Eosinophil accumulation and activation in antigen-induced late asthmatic response in guinea pigs

The purpose of this study was to investigate the participation of airway eosinophils in the antigen-induced late asthmatic response (LAR) and increased airway responsiveness in the guinea pig model of asthma. After antigen challenge, guinea pigs sensitized with aerosolized ovalbumin showed a late-phase decrease in specific airway conductance, which was accompanied by airway hyperresponsiveness to histamine, eosinophilia in the bronchoalveolar lavage fluid (BALF), decreased BALF eosinophil density, and increased generation of superoxide anions from purified BALF eosinophils. We demonstrated an association of the LAR with eosinophil accumulation and activation in the airway.

Role of cationic proteins in the airway. Hyperresponsiveness due to airway inflammation

Major basic protein (MBP) is a highly cationic protein found in the granules of eosinophils. It has been postulated that MBP may participate in the pathogenesis of airway hyperresponsiveness exhibited by asthmatic patients. Accordingly, we have employed a rat system to investigate the effect of human MBP instillation on airway responsiveness and the possible role of cationic charge in the determination of this effect. Major basic protein caused a significant increase in airway responsiveness to inhaled methacholine. Two polycations, poly-L-arginine and poly-L-lysine, also increased airway responsiveness to inhaled methacholine. Moreover, two other very different cationic proteins, platelet factor 4 (PF4) and cathepsin G were also capable of inducing airway hyperresponsiveness. These effects were dependent on their positive charge, since the charge--and, hence the effect--of these proteins was neutralized with low molecular weight heparin. In addition, other polyanions, such as low molecular weight heparin, albumin, or dextran sulfate, were also effective. We investigated whether two synthetic cationic proteins, poly-L-arginine and poly-L-lysine, could modify epithelial-dependent responses using a perfused guinea pig tracheal tube preparation. With an intact epithelium, methacholine was some 150 times less potent when applied intraluminally than when applied extraluminally. Perfusion of the luminal surface with cationic proteins increased the potency of intraluminally applied methacholine without modifying the responses to extraluminally applied methacholine. Cationic proteins also attenuated the relaxant effects of intraluminally applied KCl. These effects occurred in the absence of any overt epithelial cell damage. Our data demonstrates that cationic proteins can modify epithelial-dependent responses in the airways.(ABSTRACT TRUNCATED AT 250 WORDS)