Factors related to methacholine airway responsiveness in children

The role of small airway function parameters in preschool asthmatic children

BACKGROUND

Small airways are the major sites of inflammation and airway remodeling in all severities of asthma patients. However, whether small airway function parameters could reflect the airway dysfunction feature in preschool asthmatic children remain unclear. We aim to investigate the role of small airway function parameters in evaluating airway dysfunction, airflow limitation and airway hyperresponsiveness (AHR).

METHODS

Eight hundred and fifty-one preschool children diagnosed with asthma were enrolled retrospectively to investigate the characteristics of small airway function parameters. Curve estimation analysis was applied to clarify the correlation between small and large airway dysfunction. Spearman's correlation and receiver-operating characteristic (ROC) curves were employed to evaluate the relationship between small airway dysfunction (SAD) and AHR.

RESULTS

The prevalence of SAD was 19.5% (166 of 851) in this cross-sectional cohort study. Small airway function parameters (FEF25-75%, FEF50%, FEF75%) showed strong correlations with FEV₁% (r = 0.670, 0.658, 0.609, p<0.001, respectively), FEV₁/FVC% (r = 0.812, 0.751, 0.871, p<0.001, respectively) and PEF% (r = 0.626, 0.635, 0.530, p<0.01, respectively). Moreover, small airway function parameters and large airway function parameters (FEV₁%, FEV₁/FVC%, PEF%) were curve-associated rather than linear-related (p<0.001). FEF25-75%, FEF50%, FEF75% and FEV₁% demonstrated a positive correlation with PC₂₀ (r = 0.282, 0.291, 0.251, 0.224, p<0.001, respectively). Interestingly, FEF25-75% and FEF50% exhibited a higher correlation coefficient with PC₂₀ than FEV₁% (0.282 vs. 0.224, p = 0.031 and 0.291 vs. 0.224, p = 0.014, respectively). ROC curve analysis for predicting moderate to severe AHR showed that the area under the curve (AUC) was 0.796, 0.783, 0.738, and 0.802 for FEF25-75%, FEF50%, FEF75%, and the combination of FEF25-75% and FEF75%, respectively. When Compared to children with normal lung function, patients with SAD were slightly older, more likely to have a family history of asthma and airflow obstruction with lower FEV₁% and FEV₁/FVC%, lower PEF% and more severe AHR with lower PC₂₀ ( all p<0.05).

CONCLUSION

Small airway dysfunction is highly correlated with large airway function impairment, severe airflow obstruction and AHR in preschool asthmatic children. Small airway function parameters should be utilized in the management of preschool asthma.

Small-airway disease and its reversibility in human immunodeficiency virus-infected children on highly active antiretroviral therapy: A cross-sectional study in an African setting

BACKGROUND:

Lung function abnormalities may occur in children with human immunodeficiency virus (HIV) infection. Small-airway disease (SAD) precedes abnormalities in forced expiratory volume in 1 s (FEV ₁).

OBJECTIVE:

This study aims to assess the presence and reversibility of SAD in HIV-infected children using the Global Lung Function Initiative standards.

METHODS:

A cross-sectional study was conducted over 6 months at the Paediatric HIV Clinic of the University of Nigeria Teaching Hospital in Enugu, Southeast Nigeria. Eligible consenting children with HIV infection were recruited. Lung function was measured, and the reversibility of FEV₁ and forced vital capacity (FVC) was assessed at 12% while that of forced expiratory flow between 25% and 75% (FEF_25-75) was assessed at 12%, 15%, and 20%. Predictors of abnormal Z-score values were determined by multivariate linear and logistic regressions. Statistically significant values were set at P < 0.05.

RESULTS:

The mean Z-score for FEV₁, FVC, and FEF_25-75 was − 2.19, −1.86, and − 1.60, respectively. Most patients (73%) had abnormal FEV₁, while 52% had abnormal FEF_25-75. Significant changes in FEV₁ (P = 0.001) and FEF_25-75 (P < 0.001) occurred after the bronchodilator response (BDR) test. Of the children whose FEV₁ showed positive BDR, 70.9% had low zFEV_1; 50% had low zFEF_25-75, while all had low FEV_1. Nutritional status (Z-score for body mass index) was significantly associated with low FEV_1.

CONCLUSIONS:

Abnormal FEF_25-75 as a marker of SAD and FEV₁ with a positive BDR are common in HIV-infected children. These lung function abnormalities justify long-term follow-up for these patients.

Clinical Implications of Oscillatory Lung Function during Methacholine Bronchoprovocation Testing of Preschool Children

OBJECTIVE

To investigate the repeatability and safety of measuring impulse oscillation system (IOS) parameters and the point of wheezing during bronchoprovocation testing of preschool children.

METHODS

Two sets of methacholine challenge were conducted in 36 asthma children. The test was discontinued if there was a significant change in reactance (Xrs5) and resistance (Rrs5) at 5 Hz (Condition 1) or respiratory distress due to airway obstruction (Condition 2). The repeatability of PC₈₀_Xrs5, PC₃₀_Rrs5, and wheezing (PCw) was assessed. The changes in Z-scores and SD-indexes from prebaseline (before testing) to postbaseline (after bronchodilator) were determined.

RESULTS

For PC₃₀_Rrs5, PC₈₀_Xrs5, and PCw for subjects, PC₈₀_Xrs5 showed the highest repeatability. Fifteen of 70 tests met Condition 2. The changes from pre- and postbaseline values varied significantly for Rrs5 and Xrs5. Excluding subjects with Z-scores higher than 2SD, we were able to detect 97.1% of bronchial hyperresponsiveness during methacholine challenge based on the change in Rrs5 or Xrs5. A change in IOS parameters was associated with wheezing at all frequencies.

CONCLUSION

Xrs5 and Rrs5 have repeatability comparable with FEV1, and Xrs5 is more reliable than Rrs5. Clinicians can safely perform a challenge test by measuring the changes in Rrs5, Xrs5, and Z-scores from the prebaseline values.

Useful marker of oscillatory lung function in methacholine challenge test-comparison of reactance and resistance with dose-response slope

BACKGROUND

There are few studies focusing on the comparison of resistance (Rrs) and reactance (Xrs) in impulse oscillometry system (IOS) in the bronchial challenge test using dose-response slope (DRS), a quantitative index of bronchial hyperresponsiveness.

MATERIAL AND METHODS

We conducted a case-control study of 144 asthmatic and 218 non-asthmatic children to compare the diagnostic accuracy of two-point linear DRS for FEV1 , Rrs5 , and Xrs5 (DRS_FEV1 , DRS_Rrs5 , and DRS_Xrs5 ) and assessed various diagnostic cut-off points of provocation concentrations (PC) using receiver operating characteristic (ROC) curves.

RESULTS

DRS_FEV1 had a stronger correlation with DRS_Xrs5 (r = 0.739, P < 0.001) than with DRS_Rrs5 (r = 0.652, P < 0.001) and the area under the ROC curves of DRS_Xrs5 (0.737) was similar to that of DRS_FEV1 (0.732) and higher than that of DRS_Rrs5 (0.668). The area under the ROC curves in order of greater value was as follows: absolute change of Xrs5 (Abs_Xrs5 ) (0.759) > percent change of FEV1 (Pch_FEV1 ) (0.735) > Pch_Xrs5 (0.727) > Abs_Rrs5 (0.690) > Pch_Rrs5 (0.630). PC78 _Xrs5 and PC0.17 _Xrs5 of IOS showed considerably good sensitivity and specificity comparable to those of PC20 _FEV1 by spirometry. Additional 18 (13%) children who showed normal spirometric measures were identified as asthmatics with the use of IOS.

CONCLUSION

The utility of the DRS_Xrs5 to differentiate asthmatics from controls was comparable to that of the DRS_FEV1 and better than that of the DRS_Rrs5 . In addition, IOS could detect additional asthmatic patients who did not show positive responses in spirometry.

Bronchial hyperresponsiveness in pediatric rhinitis patients: the difference between allergic and nonallergic rhinitis

BACKGROUND

Numerous studies have examined the relationship of bronchial hyperresponsiveness (BHR) to asthma or allergic rhinitis (AR). However, little is known regarding the association between BHR and nonallergic rhinitis (NAR). This study investigated the prevalence and risk factors of BHR in pediatric patients with rhinitis and analyzed the difference between patients with AR and those with NAR.

METHODS

A total of 227 subjects with rhinitis aged 6-15 years underwent a parental survey and laboratory tests, including skin-prick test and methacholine challenge test. Outcome variables were analyzed in relation to BHR.

RESULTS

The prevalence of BHR was 55.7 and 25.5% in patients with AR and those with NAR, respectively. The persistency of rhinitis, blood eosinophil count, and baseline lung function were significantly associated with BHR in patients with AR, whereas individual or familial medical history, environmental factors, the serum immunoglobulin E level, the number of sensitized allergens, and the wheal size ratio of allergen to histamine did not affect the BHR rate. In multivariate analysis, the persistency of rhinitis was the only significant predictor of BHR in AR patients. However, persistent rhinitis symptoms did not increase the risk of BHR in NAR patients.

CONCLUSION

BHR occurs over two times more frequently in children with AR than in those with NAR. In addition, persistent nasal inflammation appears to increase the risk of BHR only in the presence of atopy.

The utility of forced expiratory flow between 25% and 75% of vital capacity in predicting childhood asthma morbidity and severity

OBJECTIVES

The forced expiratory volume in 1 second (FEV(1)) felt to be an objective measure of airway obstruction is often normal in asthmatic children. The forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) reflects small airway patency and has been found to be reduced in children with asthma. The aim of this study was to determine whether FEF(25-75) is associated with increased childhood asthma severity and morbidity in the setting of a normal FEV(1), and to determine whether bronchodilator responsiveness (BDR) as defined by FEF(25-75) identifies more childhood asthmatics than does BDR defined by FEV(1).

METHODS

The Boston Children's Hospital Pulmonary Function Test database was queried and the most recent spirometry result was retrieved for 744 children diagnosed with asthma between 10 and 18 years of age between October 2000 and October 2010. Electronic medical records in the 1 year prior and the 1 year following the date of spirometry were examined for asthma severity (mild, moderate, or severe) and morbidity outcomes for the three age, race, and gender-matched subgroups: Group A (n = 35) had a normal FEV(1), FEV(1)/forced vital capacity (FVC), and FEF(25-75); Group B (n = 36) had solely a diminished FEV(1)/FVC; and Group C (n = 37) had a normal FEV(1), low FEV(1)/FVC, and low FEF(25-75). Morbidity outcomes analyzed included the presence of hospitalization, emergency department visit, intensive care unit admission, asthma exacerbation, and systemic steroid use.

RESULTS

Subjects with a low FEF(25-75) (Group C) had nearly 3 times the odds ratio (OR) (OR = 2.8, p < .01) of systemic corticosteroid use and 6 times the OR of asthma exacerbations (OR = 6.3, p > .01) compared with those who had normal spirometry (Group A). Using FEF(25-75) to define BDR identified 53% more subjects with asthma than did using a definition based on FEV(1).

CONCLUSIONS

A low FEF(25-75) in the setting of a normal FEV(1) is associated with increased asthma severity, systemic steroid use, and asthma exacerbations in children. In addition, using the percent change in FEF(25-75) from baseline may be helpful in identifying BDR in asthmatic children with a normal FEV(1).

Gastroesophageal reflux disease and airway hyperresponsiveness: concomitance beyond the realm of chance?

Gastroesophageal reflux disease and asthma are both quite common the world over, and they can coexist. However, the nature of the relationship between these two diseases remains unclear. In this study, we review controversial aspects of the relationships among asthma, airway hyperresponsiveness, and gastroesophageal reflux disease in adults and in children.

Bronchial hyperresponsiveness decreases through childhood

Limited knowledge exists about development of bronchial hyperresponsiveness (BHR) through adolescence. We aimed to assess changes in and risk factors for BHR in adolescence. From a Norwegian birth cohort 517 subjects underwent clinical examinations, structured interviews and methacholine challenges at age 10 and 16. BHR was divided into four categories: no BHR (cumulative methacholine dose required to reduce FEV(1) by 20% (PD(20)) >16 μmol), borderline BHR (PD(20) ≤16 and >8 μmol), mild to moderate BHR (PD(20) ≤8 and >1 μmol), and severe BHR (PD(20) ≤ 1 μmol). Logistic regression analysis was used to assess risk factors and possible confounders. The number of children with PD(20) ≤ 8 decreased from 172 (33%) to 79 (15%) from age 10-16 (p < 0.001). Most children (n = 295, 57%) remained in the same BHR (category) from age 10-16 (50% with no BHR), whereas the majority 182 (82%) of the 222 children who changed BHR category, had decreased severity at age 16. PD(20) ≤ 8 at age 10 was the major risk factor for PD(20) ≤ 8 6 years later (odds ratio 6.3), without significant confounding effect (>25% change) of gender, active rhinitis, active asthma, height, FEV(1)/FVC, or allergic sensitization. BHR decreased overall in severity through adolescence, was stable for the majority of children and only a minority (8%) had increased BHR from age 10 to 16. Mild to moderate and severe BHR at age 10 were major risk factors for PD(20) ≤ 8 at 16 years and not modified by asthma or body size.

Airway hyperresponsiveness in children with sickle cell anemia

BACKGROUND

The high prevalence of airway hyperresponsiveness (AHR) among children with sickle cell anemia (SCA) remains unexplained.

METHODS

To determine the relationship between AHR, features of asthma, and clinical characteristics of SCA, we conducted a multicenter, prospective cohort study of children with SCA. Dose response slope (DRS) was calculated to describe methacholine responsiveness, because 30% of participants did not achieve a 20% decrease in FEV1 after inhalation of the highest methacholine concentration, 25 mg/mL. Multiple linear regression analysis was done to identify independent predictors of DRS.

RESULTS

Methacholine challenge was performed in 99 children with SCA aged 5.6 to 19.9 years (median, 12.8 years). Fifty-four (55%) children had a provocative concentration of methacholine producing a 20% decrease in FEV1<4 mg/mL. In a multivariate analysis, independent associations were found between increased methacholine responsiveness and age (P<.001), IgE (P=.009), and lactate dehydrogenase (LDH) levels (P=.005). There was no association between methacholine responsiveness and a parent report of a doctor diagnosis of asthma (P=.986). Other characteristics of asthma were not associated with methacholine responsiveness, including positive skin tests to aeroallergens, exhaled nitric oxide, peripheral blood eosinophil count, and pulmonary function measures indicating airflow obstruction.

CONCLUSIONS

In children with SCA, AHR to methacholine is prevalent. Younger age, serum IgE concentration, and LDH level, a marker of hemolysis, are associated with AHR. With the exception of serum IgE, no signs or symptoms of an allergic diathesis are associated with AHR. Although the relationship between methacholine responsiveness and LDH suggests that factors related to SCA may contribute to AHR, these results will need to be validated in future studies.

Forced expiratory flow between 25% and 75% of vital capacity and FEV1/forced vital capacity ratio in relation to clinical and physiological parameters in asthmatic children with normal FEV1 values

BACKGROUND

The assumption that the assessment of forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) does not provide additional information in asthmatic children with normal FEV(1) percent predicted has not been adequately tested.

OBJECTIVE

We sought to determine whether the measurement of FEF(25-75) percent predicted offers advantages over FEV(1) percent predicted and FEV(1)/forced vital capacity (FVC) percent predicted for the evaluation of childhood asthma.

METHODS

This is a secondary analysis of data from the Pediatric Asthma Controller Trial and the Characterizing the Response to a Leukotriene Receptor Antagonist and Inhaled Corticosteroid trials. Pearson correlation coefficients, Pearson partial correlation coefficients, canonical correlations, and receiver operating characteristic (ROC) curves were constructed.

RESULTS

Among 437 children with normal FEV(1) percent predicted, FEF(25-75) percent predicted, and FEV(1)/FVC percent predicted were (1) positively correlated with log(2) methacholine PC(20), (2) positively correlated with morning and evening peak expiratory flow percent predicted, and (3) negatively correlated with log(10) fraction of exhaled nitric oxide and bronchodilator responsiveness. Pearson partial correlations and canonical correlations indicated that FEF(25-75) percent predicted was better correlated with bronchodilator responsiveness and log(2) methacholine PC(20) than were FEV(1) percent predicted or FEV(1)/FVC percent predicted. In the ROC curve analysis, FEF(25-75) at 65% of predicted value had a 90% sensitivity and a 67% specificity for detecting a 20% increase in FEV(1) after albuterol inhalation.

CONCLUSION

FEF(25-75) percent predicted was well correlated with bronchodilator responsiveness in asthmatic children with normal FEV(1). FEF(25-75) percent predicted should be evaluated in clinical studies of asthma in children and might be of use in predicting the presence of clinically relevant reversible airflow obstruction.

Factors affecting bronchial hyperreactivity in asthmatic children

Bronchial hyperresponsiveness (BHR), the exaggerated airway narrowing in response to nonspesific stimuli, is a common characteristic of asthma. One hundred thirty-five children who were diagnosed asthma in the outpatient clinic of Gazi University Hospital, Pediatric Allergy and Asthma Department between January 2007 and January 2008 were retrospectively analysed from the asthma database of the division. BHR was not found to be different according to sex. Younger the age of the patient, more severe was BHR (p = 0.096, r = 0.164). Younger the age at onset of the symptoms, the more severe was the BHR (p < 0.001, r = 0.307). Patients who had an asthmatic first degree relative and who were exposed to passive smoking at home, had more severe BHR (p = 0.006 and p = 0.032, respectively). There were more hospitalizations among the asthmatic children with moderate-severe BHR (p = 0.027) however no correlation was found between chronic asthma severity and the degree of BHR). In this study we found that age, age at onset of symptoms, having a parent with asthma, exposure to tobacco smoke and baseline lung function are related to BHR measured at referral. Serum levels of Ig E or skin prick test positivity were not found to have any effect on BHR severity. Considering BHR severity, we could not reveal any relation between atopic and nonatopic children. However among atopic subjects, the ones with indoor allergen sensitization had more severe BHR.

Lung function, bronchial responsiveness, and asthma in a community cohort of 6-year-old children

KEYWORDS

Children as young as 6 years old can perform spirometry, yet the relationship between current asthma, lung function, and bronchial responsiveness has not been described at this age; 2,537 children from a community-based birth cohort were assessed at 6 years of age, with history (n = 2,141), physical examination (n = 1,995), standard spirometry (n = 1,735), and a random sample (n = 711) offered methacholine challenge. Males had greater values of FVC and FEV(1) but not of mean forced expiratory flow during the middle half of the FVC or FEV(1)/FVC than females. The greatest influences on lung function at 6 years were height, sex, birth weight, and wheezing in the first year of life. Children with current asthma had small but significant deficits in lung function and were more sensitive to methacholine. The optimal cutpoint for determining heightened bronchial responsiveness was found to be a 15% fall in FEV(1) at a dose of 1.8 mg/ml. A negative test could be useful in excluding a diagnosis of asthma (negative predictive value of 92%). Lung function testing, including methacholine challenge, is feasible in 5- to 7-year-old children and has the potential to contribute to the clinical management of children with asthma.

Correction of bronchial challenge data for age and size may affect the results of genetic association studies in children

Meaningful studies of asthma genetics require careful definition of airway hyperresponsiveness (AHR). In children, several studies have emphasized the need for correction of bronchial challenge data for baseline parameters, such as age, gender, lung function and atopic status, when undertaking airway responsiveness measurements. However, few studies have suggested how this should be performed in practice. This study describes a method for the correction of dose-response slopes (DRS) and PC20 values for baseline parameters in children, and illustrates the effect of such corrections on the association of AHR with the glutathione S-transferase GSTP1 Ile105Val polymorphism in children. Skin prick and methacholine challenge testing, measurement of total serum IgE concentration and GSTP1 genotyping were performed in 145 unrelated British children aged 7-18 years. Correction of bronchial challenge results, expressed as both DRS and PC20 values, for age, gender, baseline lung function and atopic status was performed using linear regression and discriminant analysis, respectively. Adjusting bronchial challenge results for the age and size of the child altered AHR status, defined as a PC20 methacholine <8 mg/ml, in 37% of children. Correction for baseline parameters also resulted in a significant reduction in mean DRS (original uncorrected DRS 83.6, corrected DRSc 27.4). This had a marked effect on the results of the association study, unmasking a previously unidentified association between the GSTP1 genotype and AHR in children. Age and size adjustment of bronchial challenge data has a significant effect on AHR status and may influence the results of genetic association studies in children.

Determinants of airway hyperresponsiveness in mild asthma

BACKGROUND

Patients with mild asthma may have coexisting severe airway hyperresponsiveness (AHR), although the reasons for this are uncertain.

OBJECTIVE

To evaluate the factors that determine AHR in mild asthma.

METHODS

We performed a retrospective database evaluation of two groups of patients with mild asthma with forced expiratory volume in 1 second (FEV1) of 80% or more than predicted. Group A (n = 92; mean inhaled corticosteroid dose, 491 microg) had moderate-to-severe AHR to methacholine (provocative dose causing a 20% decrease in FEV1 [methacholine PD20], < or = 100 microg), whereas group B (n = 92; mean inhaled corticosteroid dose, 509 microg) had borderline AHR (methacholine PD20, > or = 800 microg). Both groups were matched for age, sex, inhaled corticosteroid use, and FEV1.

RESULTS

From our database, we found 361 patients with an FEV1 of 80% or more than predicted of whom 123 (34%) had a methacholine PD20 of 100 microg or less and 138 (38%) had a methacholine PD20 of 800 microg or more. The methacholine PD20 geometric means (geometric SE) of groups A and B were 25 microg (3 microg) and 5,392 microg (295 microg), respectively. Despite matched mean values for FEV1, compared with group B, group A had a lower predicted forced expiratory flow between 25% and 75% (71% vs 81%, P = 0.007). A greater proportion of group A compared with group B patients were sensitized to house-dust mite (76% vs 54%, P = 0.002). No significant differences were found between groups in terms of presence of rhinitis and sensitization to other individual aeroallergens.

CONCLUSIONS

Increased sensitization to house-dust mite and reduced small airway caliber were associated with moderate-to-severe AHR in mild asthma. Skin prick testing to common aeroallergens, especially house-dust mite, should be a routine part in the evaluation of asthmatic patients, including those patients with mild disease.

Relationship of house-dust mite allergen exposure in children's bedrooms in infancy to bronchial hyperresponsiveness and asthma diagnosis by age 6 to 7

BACKGROUND

Several studies have suggested that exposure to house-dust mite (HDM) allergen in infancy increases the risk of developing asthma.

OBJECTIVE

To determine whether exposure to higher levels of dust mite in infants increased the risk of developing bronchial hyperresponsiveness (BHR) or physician-diagnosed asthma by age 6 to 7 years.

METHODS

A health maintenance organization-based cohort of 97 middle class suburban children born from 1987 to 1989 with a high cord blood immunoglobulin E, defined as > or = 0.56 IU/mL, was followed as a part of the Childhood Allergy Study. During the first 2 years of life, monthly bedroom dust samples were collected and analyzed for Der f 1 and Der p 1. Between 6 and 7 years of age, 64 of the original cohort answered a questionnaire used to determine the presence of physician-diagnosed asthma, underwent clinical examination, skin prick testing, and methacholine inhalation challenge. Mann-Whitney tests were used to compare Der f 1 and Der p 1 levels in homes of children with and without BHR, and those with and without physician-diagnosed asthma.

RESULTS

In all, 1,421 dust samples were collected and assayed. No significant differences were seen in either the mean, maximum, or minimum dust mite allergen levels in homes of children with versus without BHR, or children with versus without asthma. However, sensitization to HDM was associated with physician-diagnosed asthma (P < 0.05).

CONCLUSIONS

When compared with other studies, we were able to more accurately estimate the level of dust mite allergen exposure through repeated sampling over a relatively long period, incorporating seasonal variations. Although HDM sensitization and asthma were concurrently related, we were unable to find any relationship between level of HDM allergen exposure in children's bedrooms in early childhood and development of BHR or physician-diagnosed asthma by age 6 to 7 years.

How should a birth cohort study be organised? Experience from the German MAS cohort study

Birth cohort studies offer the opportunity to study average risks, rates and occurrence times of disease longitudinally from birth. The effect of genetic and environmental factors and their interactions can be studied. Furthermore, quantity and duration of exposure to environmental agents can be evaluated prospectively. However, prospective birth cohort studies are expensive, labour intensive and take many years to complete. Loss of subjects over time as well as recall bias complicate the interpretation of observations. This paper summarises the potential pitfalls of such studies and discusses the experience of the German Multicentre Allergy Study (MAS), which began in 1990 in five German cities and included 1314 newborns for the study of the natural course of atopic diseases.

Distinct spatial requirement for eosinophil-induced airways hyperreactivity

T helper (Th)-2-derived cytokines and their involvement in the recruitment and activation of inflammatory cells crucially orchestrate asthma pathogenesis. A notable cellular component of this allergy-induced inflammation is the eosinophil. However, whether the eosinophil is an obligatory mediator for enhancing airways hyperreactivity (AHR) to cholinergic stimuli, a watershed of the asthmatic lung, is somewhat controversial. In this investigation we have endeavoured to define the spatial requirements for IL-4 and IL-13, and the downstream effector molecules, IL-5 and the CC chemokine eotaxin, for the recruitment of eosinophils and the development of AHR in a murine model of allergic pulmonary disease. These studies are of particular importance considering clinical trials, with either the soluble IL-4Ralpha subunit or a humanized anti-IL-5 antibody, are being conducted. Interestingly, our studies show that depletion of both IL-4 and IL-13 is necessary to ablate pulmonary eosinophilia and AHR, and that this may be attributed to the role these cytokines play in regulating the expression of the eosinophil- activating molecules, IL-5 and eotaxin. While it is clear that depletion of IL-5 diminishes pulmonary eosinophilia, we demonstrate in BALB/c mice that a deficiency in both IL-5 and eotaxin is necessary to abolish both the trafficking of eosinophils to the lung and AHR. However, in contrast to the neutrophil-rich inflammation observed in mice deficient in both IL-4 and IL-13, inflammation per se in mice deficient in both IL-5 and eotaxin is significantly attenuated. This suggests that asthma immunotherapy may be better directed towards the eosinophil- activating molecules IL-5 and eotaxin, rather than towards pleiotrophic molecules such IL-4 and IL-13, which are additionally important in modulating alternative inflammatory responses.