Genes in asthma: new genes and new ways

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

Investigating the regulatory role of ORMDL3 in airway barrier dysfunction using in vivo and in vitro models

The airway epithelium (AE) is the main protective barrier between the host and external environmental factors causing asthma. Allergens or pathogens induce AE dysfunction, including epithelial permeability alteration, trans‑epithelial electrical resistance (TEER) reduction, upregulation of inflammatory mediators and downregulation of junctional complex molecules. Orosomucoid‑like protein isoform 3 (ORMDL3), a gene closely associated with childhood onset asthma, is involved in airway inflammation and remodeling. It was hypothesized that ORMDL3 plays an important role in regulating AE barrier function. In vivo [chronic asthma induced by ovalbumin‑respiratory syncytial virus (OVA‑RSV)] in mice) and in vitro (human bronchial epithelial cells and 16HBE cells) models were used to assess ORMDL3's role in AE function regulation, evaluating paracellular permeability, TEER and the expression levels of junctional complex molecules. The effects of ORMDL3 on the extracellular signal‑regulated protein kinase (ERK) pathway were determined. In mice with OVA‑RSV induced chronic asthma, ORMDL3 and sphingosine kinase 1 (SPHK1) were upregulated whereas the junction related proteins Claudin‑18 and E‑cadherin were downregulated. Overexpression of ORMDL3 resulted in decreased TEER, downregulation of junctional complex molecules and induced epithelial permeability. In contrast, ORMDL3 inhibition showed the opposite effects. In 16HBE cells, ORMDL3 overexpression induced SPHK1 distribution and activity, while SPHK1 inhibition resulted in increased TEER upon administration of an ORMDL3 agonist or ORMDL3 overexpression. In addition, ERK activation occurred downstream of SPHK1 activation in 16HBE cells. High levels of ORMDL3 result in damaged AE barrier function by inducing the SPHK1/ERK pathway.

Variants in the IL17 pathway genes are associated with atopic asthma and atopy makers in a South American population

BACKGROUND

Asthma is a complex disorder with multiple phenotypes which can influence its severity and response to treatment. The TH17 lymphocytes producing IL-17A and IL17-F cytokines, may have a role on asthma inflammation. The aim of our study was to evaluate the association between genetic variants in IL17 pathway genes with asthma and atopy markers.

MATERIALS AND METHODS

Genotyping was performed using a commercial panel in 1245 participants of SCAALA cohort. The study included 91 SNVs in IL-17 pathway genes. Logistic regressions for asthma and atopy markers were performed using PLINK 1.9. In silico analyses were performed using rSNPbase, RegulomeDB, and Gtex portal for in silico gene expression.

RESULTS AND DISCUSSION

The T allele of rs1974226 in IL17A was positively associated with asthma (OR: 1.37; 95% CI 1.02-1.82). Also, the T allele of rs279548 was positively associated with asthma (OR: 1.30; 95% CI 1.02-1.64), atopy (OR: 1.62; 95% CI 1.05-2.50) and increased expression of the IL17RC in lung and whole blood tissues. The others genetic variants in the IL17 pathways genes were associated with both protection and risk for asthma development as well as with IgE levels.

CONCLUSION

The genetic variants in IL-17-related genes are associated with the atopic asthma phenotype and IgE production.

Functional characterization of lysosomal interaction of Akt with VRK2

Serine-threonine kinase Akt (also known as PKB, protein kinase B), a core intracellular mediator of cell survival, is involved in various human cancers and has been suggested to play an important role in the regulation of autophagy in mammalian cells. Nonetheless, the physiological function of Akt in the lysosomes is currently unknown. We have reported previously that PtdIns(3)P-dependent lysosomal accumulation of the Akt-Phafin2 complex is a critical step for autophagy induction. Here, to characterize the molecular function of activated Akt in the lysosomes in the process of autophagy, we searched for the molecules that interact with the Akt complex at the lysosomes after induction of autophagy. By time-of-flight-mass spectrometry (TOF/MS) analysis, kinases of the VRK family, a unique serine-threonine family of kinases in the human kinome, were identified. VRK2 interacts with Akt1 and Akt2, but not with Akt3; the C terminus of Akt and the N terminus of VRK2 facilitate the interaction of Akt and VRK2 in mammalian cells. The kinase-dead form of VRK2A (KD VRK2A) failed to interact with Akt in coimmunoprecipitation assays. Bimolecular fluorescence complementation (BiFC) experiments showed that, in the lysosomes, Akt interacted with VRK2A but not with VRK2B or KD VRK2A. Immunofluorescent assays revealed that VRK2 and phosphorylated Akt accumulated in the lysosomes after autophagy induction. WT VRK2A, but not KD VRK2A or VRK2B, facilitated accumulation of phosphorylated Akt in the lysosomes. Downregulation of VRK2 abrogated the lysosomal accumulation of phosphorylated Akt and impaired nuclear localization of TFEB; these events coincided to inhibition of autophagy induction. The VRK2-Akt complex is required for control of lysosomal size, acidification, bacterial degradation, and for viral replication. Moreover, lysosomal VRK2-Akt controls cellular proliferation and mitochondrial outer-membrane stabilization. Given the roles of autophagy in the pathogenesis of human cancer, the current study provides a novel insight into the oncogenic activity of VRK2-Akt complexes in the lysosomes via modulation of autophagy.

Gene editing in the context of an increasingly complex genome

The reporting of the first draft of the human genome in 2000 brought with it much hope for the future in what was felt as a paradigm shift toward improved health outcomes. Indeed, we have now mapped the majority of variation across human populations with landmark projects such as 1000 Genomes; in cancer, we have catalogued mutations across the primary carcinomas; whilst, for other diseases, we have identified the genetic variants with strongest association. Despite this, we are still awaiting the genetic revolution in healthcare to materialise and translate itself into the health benefits for which we had hoped. A major problem we face relates to our underestimation of the complexity of the genome, and that of biological mechanisms, generally. Fixation on DNA sequence alone and a 'rigid' mode of thinking about the genome has meant that the folding and structure of the DNA molecule -and how these relate to regulation- have been underappreciated. Projects like ENCODE have additionally taught us that regulation at the level of RNA is just as important as that at the spatiotemporal level of chromatin.In this review, we chart the course of the major advances in the biomedical sciences in the era pre- and post the release of the first draft sequence of the human genome, taking a focus on technology and how its development has influenced these. We additionally focus on gene editing via CRISPR/Cas9 as a key technique, in particular its use in the context of complex biological mechanisms. Our aim is to shift the mode of thinking about the genome to that which encompasses a greater appreciation of the folding of the DNA molecule, DNA- RNA/protein interactions, and how these regulate expression and elaborate disease mechanisms.Through the composition of our work, we recognise that technological improvement is conducive to a greater understanding of biological processes and life within the cell. We believe we now have the technology at our disposal that permits a better understanding of disease mechanisms, achievable through integrative data analyses. Finally, only with greater understanding of disease mechanisms can techniques such as gene editing be faithfully conducted.

Whole-genome sequencing of individuals from a founder population identifies candidate genes for asthma

Asthma is a complex genetic disease caused by a combination of genetic and environmental risk factors. We sought to test classes of genetic variants largely missed by genome-wide association studies (GWAS), including copy number variants (CNVs) and low-frequency variants, by performing whole-genome sequencing (WGS) on 16 individuals from asthma-enriched and asthma-depleted families. The samples were obtained from an extended 13-generation Hutterite pedigree with reduced genetic heterogeneity due to a small founding gene pool and reduced environmental heterogeneity as a result of a communal lifestyle. We sequenced each individual to an average depth of 13-fold, generated a comprehensive catalog of genetic variants, and tested the most severe mutations for association with asthma. We identified and validated 1960 CNVs, 19 nonsense or splice-site single nucleotide variants (SNVs), and 18 insertions or deletions that were out of frame. As follow-up, we performed targeted sequencing of 16 genes in 837 cases and 540 controls of Puerto Rican ancestry and found that controls carry a significantly higher burden of mutations in IL27RA (2.0% of controls; 0.23% of cases; nominal p = 0.004; Bonferroni p = 0.21). We also genotyped 593 CNVs in 1199 Hutterite individuals. We identified a nominally significant association (p = 0.03; Odds ratio (OR) = 3.13) between a 6 kbp deletion in an intron of NEDD4L and increased risk of asthma. We genotyped this deletion in an additional 4787 non-Hutterite individuals (nominal p = 0.056; OR = 1.69). NEDD4L is expressed in bronchial epithelial cells, and conditional knockout of this gene in the lung in mice leads to severe inflammation and mucus accumulation. Our study represents one of the early instances of applying WGS to complex disease with a large environmental component and demonstrates how WGS can identify risk variants, including CNVs and low-frequency variants, largely untested in GWAS.

The innovation journey of genomics and asthma research

This article concerns the transformative potential of medical genomics for common disease research. We analysed 13 review articles in asthma research in the period 1999 to 2008. Our aim was to understand how genomics has emerged in this research field, and the attendant changes. Motivated by Lippman's geneticisation thesis, we use the concept of an 'innovation journey' to trace how expectations of improved understanding, prevention, diagnosis and treatment structure a dynamic co-evolutionary process through which a genome-based discourse emerges. We show how the asthma researchers involved continuously struggle to define their contribution to asthma research, as well as to clinical practice. Along the way, the researchers propose changes to both the definition and the aetiological model of asthma, thus highlighting gene-gene and gene-environment interactions. It is, however, difficult to characterise this discourse as one of geneticisation. With increasing attention being given to epigenetics, metabolomics, proteomics and systems biology, the emerging picture suggests an important, but much less deterministic, role for genes.

Genome Wide Association Study to predict severe asthma exacerbations in children using random forests classifiers

BACKGROUND

Personalized health-care promises tailored health-care solutions to individual patients based on their genetic background and/or environmental exposure history. To date, disease prediction has been based on a few environmental factors and/or single nucleotide polymorphisms (SNPs), while complex diseases are usually affected by many genetic and environmental factors with each factor contributing a small portion to the outcome. We hypothesized that the use of random forests classifiers to select SNPs would result in an improved predictive model of asthma exacerbations. We tested this hypothesis in a population of childhood asthmatics.

METHODS

In this study, using emergency room visits or hospitalizations as the definition of a severe asthma exacerbation, we first identified a list of top Genome Wide Association Study (GWAS) SNPs ranked by Random Forests (RF) importance score for the CAMP (Childhood Asthma Management Program) population of 127 exacerbation cases and 290 non-exacerbation controls. We predict severe asthma exacerbations using the top 10 to 320 SNPs together with age, sex, pre-bronchodilator FEV1 percentage predicted, and treatment group.

RESULTS

Testing in an independent set of the CAMP population shows that severe asthma exacerbations can be predicted with an Area Under the Curve (AUC)=0.66 with 160-320 SNPs in comparison to an AUC score of 0.57 with 10 SNPs. Using the clinical traits alone yielded AUC score of 0.54, suggesting the phenotype is affected by genetic as well as environmental factors.

CONCLUSIONS

Our study shows that a random forests algorithm can effectively extract and use the information contained in a small number of samples. Random forests, and other machine learning tools, can be used with GWAS studies to integrate large numbers of predictors simultaneously.

Association between single-nucleotide polymorphisms in pre-miRNAs and the risk of asthma in a Chinese population

Single-nucleotide polymorphisms (SNPs) in pre-miRNAs may alter microRNA (miRNA) expression levels or processing and contribute to susceptibility to a wide range of diseases. We investigated the correlation between four SNPs (rs11614913, rs3746444, rs2910164, and rs229283) in pre-miRNAs and the risk of asthma in 220 asthma patients and 540 controls using polymerase chain reaction-restriction fragment length polymorphism methodology and DNA-sequencing. There were significant differences in the genotype and allelic distribution of rs2910164G/C and rs2292832C/T polymorphisms among cases and controls. The CC genotype and C allele of rs2910164G/C were significantly associated with a decreased risk of asthma (CC vs. GG, odds ratio [OR] = 0.51, 95% confidence interval [CI]: 0.31-0.82; C vs. G, OR = 0.74, 95% CI: 0.59-0.93). Similarly, the TT genotype and T allele of rs2292832C/T were significantly associated with a decreased risk of asthma (TT vs. CC, OR = 0.56, 95% CI: 0.33-0.95; T vs. C, OR = 0.71, 95% CI: 0.53-0.95). However, no significant association between the other two polymorphisms (i.e., rs11614913C/T and rs3746444C/T) and the risk of asthma was observed. Our data indicate that rs2910164G/C and rs2292832C/T may play a role in the development of asthma.

Exposure assessment in cohort studies of childhood asthma

BACKGROUND

The environment is suspected to play an important role in the development of childhood asthma. Cohort studies are a powerful observational design for studying exposure-response relationships, but their power depends in part upon the accuracy of the exposure assessment.

OBJECTIVE

The purpose of this paper is to summarize and discuss issues that make accurate exposure assessment a challenge and to suggest strategies for improving exposure assessment in longitudinal cohort studies of childhood asthma and allergies.

DATA SYNTHESIS

Exposures of interest need to be prioritized, because a single study cannot measure all potentially relevant exposures. Hypotheses need to be based on proposed mechanisms, critical time windows for effects, prior knowledge of physical, physiologic, and immunologic development, as well as genetic pathways potentially influenced by the exposures. Modifiable exposures are most important from the public health perspective. Given the interest in evaluating gene-environment interactions, large cohort sizes are required, and planning for data pooling across independent studies is critical. Collection of additional samples, possibly through subject participation, will permit secondary analyses. Models combining air quality, environmental, and dose data provide exposure estimates across large cohorts but can still be improved.

CONCLUSIONS

Exposure is best characterized through a combination of information sources. Improving exposure assessment is critical for reducing measurement error and increasing power, which increase confidence in characterization of children at risk, leading to improved health outcomes.

The emerging role of microRNAs in asthma

Asthma is a common chronic airways disease that worldwide affects people from all ethnic backgrounds. MicroRNAs (miRNAs) are small non-coding RNAs of 18-25 nucleotides that have been shown to regulate gene expression via the RNA interference pathway and found to play fundamental roles in diverse biological and pathological processes. Intriguingly, changes in the expression of several miRNAs are associated with development of asthma. In this review, we summarize the current understanding of the role of miRNAs in asthma to both better understand the pathogenesis of this disease and aid in the formulation of more effective therapeutic strategies.

Immunological and genetic aspects of asthma and allergy

Prevalence of allergy and allergic asthma are increasing worldwide. More than half of the US population has a positive skin prick test and approximately 10% are asthmatics. Many studies have been conducted to define immunological pathways underlying allergy and asthma development and to identify the main genetic determinants. In the effort to find missing pieces of the puzzle, new genomic approaches and more standardized ones, such as the candidate gene approach, have been used collectively. This article proposes an overview of the actual knowledge about immunological and genetic aspects of allergy and asthma. Special attention has been drawn to the challenges linked to genetic research in complex traits such as asthma and to the contribution of new genomic approaches.

New insight into the genes susceptible to asthma

There is considerable worldwide interest in identifying genes related to susceptibility to asthma. Progress has been slow in part because of the complexity and heterogeneity of the disease. Although at least 170 genes located on 10 chromosomes have been associated with or in linkage with asthma and asthma-related phenotypes, the majority of the reports have either been preliminary or the results have been controversial. In order to overcome the problems with the inherent complexity of asthma and methodological issues, the authors propose a strategy for identification of asthma susceptibility genes based on theories of systems biology and bioinformatics and candidate gene approach.

Time-series nasal epithelial transcriptomics during natural pollen exposure in healthy subjects and allergic patients

BACKGROUND

The role of epithelium has recently awakened interest in the studies of type I hypersensitivity.

OBJECTIVE

We analysed the nasal transcriptomics epithelial response to natural birch pollen exposure in a time series manner.

METHODS

Human nasal epithelial cell swabs were collected from birch pollen allergic patients and healthy controls in winter season. In addition, four specimens at weekly intervals were collected from the same subjects during natural birch pollen exposure in spring and transcriptomic analyses were performed.

RESULTS

The nasal epithelium of healthy subjects responded vigorously to allergen exposure. The immune response was a dominating category of this response. Notably, the healthy subjects did not display any clinical symptoms regardless of this response detected by transcriptomic analysis. Concomitantly, the epithelium of allergic subjects responded also, but with a different set of responders. In allergic patients the regulation of dyneins, the molecular motors of intracellular transport dominated. This further supports our previous hypothesis that the birch pollen exposure results in an active uptake of allergen into the epithelium only in allergic subjects but not in healthy controls.

CONCLUSION

We showed that birch pollen allergen causes a defence response in healthy subjects, but not in allergic subjects. Instead, allergic patients actively transport pollen allergen through the epithelium to tissue mast cells. Our study showed that new hypotheses can arise from the application of discovery driven methodologies. To understand complex multifactorial diseases, such as type I hypersensitivity, this kind of hypotheses might be worth further analyses.

Asma infantil y del lactante

El asma es la enfermedad crónica más frecuente de la infancia. El diagnóstico suele ser fácil cuando se producen episodios de disnea espiratoria con sibilancias reversibles de forma espontánea o mediante el uso de broncodilatadores. Las radiografías de tórax, la exploración funcional respiratoria y el estudio alérgico constituyen el aspecto fundamental de las pruebas complementarias necesarias. El tratamiento de la crisis consiste en el uso de β2-adrenérgicos inhalados y, si es necesario, corticoides orales. El tratamiento de fondo tiene como objetivo limitar al máximo los síntomas y restaurar o mantener las funciones pulmonares normales. Se debe adaptar a la gravedad y al control de la enfermedad y los corticoides inhalados tienen un papel de elección.

Identification of novel chromosomal regions associated with airway hyperresponsiveness in recombinant congenic strains of mice

Airway responsiveness is the ability of the airways to respond to bronchoconstricting stimuli by reducing their diameter. Airway hyperresponsiveness has been associated with asthma susceptibility in both humans and murine models, and it has been shown to be a complex and heritable trait. In particular, the A/J mouse strain is known to have hyperresponsive airways, while the C57BL/6 strain is known to be relatively refractory to bronchoconstricting stimuli. We analyzed recombinant congenic strains (RCS) of mice generated from these hyper- and hyporesponsive parental strains to identify genetic loci underlying the trait of airway responsiveness in response to methacholine as assessed by whole-body plethysmography. Our screen identified 16 chromosomal regions significantly associated with airway hyperresponsiveness (genome-wide P <or= 0.05): 8 are supported by independent and previously published reports while 8 are entirely novel. Regions that overlap with previous reports include two regions on chromosome 2, three on chromosome 6, one on chromosome 15, and two on chromosome 17. The 8 novel regions are located on chromosome 1 (92-100 cM), chromosome 5 (>73 cM), chromosome 7 (>63 cM), chromosome 8 (52-67 cM), chromosome 10 (3-7 cM and >68 cM), and chromosome 12 (25-38 cM and >52 cM). Our data identify several likely candidate genes from the 16 regions, including Ddr2, Hc, Fbn1, Flt3, Utrn, Enpp2, and Tsc.

Genetics terminology for respiratory physicians

Genes affect our susceptibility to almost all diseases, from the rare single gene disorders such as cystic fibrosis to common multifactorial disorders such as asthma. They also influence our response to specific therapies. Scientific advances in genetics, starting with projects such as the mapping of the human genome [International Human Genome Sequencing Consortium. Finishing the euchromatic sequence of the human genome. Nature 2004; 431: 931-945] are likely to improve healthcare in the coming decades. Internationally, government initiatives have been established to address strategies to implement these changes [NHS Genetics White Paper. "Our Inheritance - Our Future": Realising the potential of Genetics in the NHS. UK: Department of Health 2003; Family Health History Initiative. National Human Genome Research Institute and Office of Surgeon General, Department of Health and Human Services. 2004]. A knowledge of basic genetic principles and familiarity with genetic 'jargon' associated with new technologies will be important for those practicing in this era of 'genomic medicine' [Collins FS, Green ED, Guttmacher AE, Guyer MS. A vision for the future of genomics research. Nature 2003; 422; April 24; 835-847]. The aim of this article is to review genetic terminology using examples from paediatric respiratory medicine.

Genetic variation of genes for xenobiotic-metabolizing enzymes and risk of bronchial asthma: the importance of gene-gene and gene-environment interactions for disease susceptibility

The aim of our pilot study was to evaluate the contribution of genes for xenobiotic-metabolizing enzymes (XMEs) for the development of bronchial asthma. We have genotyped 25 polymorphic variants of 18 key XME genes in 429 Russians, including 215 asthmatics and 214 healthy controls by a polymerase chain reaction, followed by restriction fragment length polymorphism analyses. We found for the first time significant associations of CYP1B1 V432L (P=0.045), PON1 Q192R (P=0.039) and UGT1A6 T181A (P=0.025) gene polymorphisms with asthma susceptibility. Significant P-values were evaluated through Monte-Carlo simulations. The multifactor-dimensionality reduction method has obtained the best three-locus model for gene-gene interactions between three loci, EPHX1 Y113H, CYP1B1 V432L and CYP2D6 G1934A, in asthma at a maximum cross-validation consistency of 100% (P=0.05) and a minimum prediction error of 37.8%. We revealed statistically significant gene-environment interactions (XME genotypes-smoking interactions) responsible for asthma susceptibility for seven XME genes. A specific pattern of gametic correlations between alleles of XME genes was found in asthmatics in comparison with healthy individuals. The study results point to the potential relevance of toxicogenomic mechanisms of bronchial asthma in the modern world, and may thereby provide a novel direction in the genetic research of the respiratory disease in the future.

Mucosal immunology of geohelminth infections in humans

There is limited data on the human mucosal immune response to geohelminths, but extensive data from experimental animals. Geohelminth infections may modulate mucosal immunity with effects on parasite expulsion or persistence and mucosal inflammation. Geohelminths are considered to have important effects on immunity to mucosal vaccines, infectious disease susceptibility, and anti-inflammatory effects in inflammatory bowel disease and asthma. This review will discuss the findings of studies of human immunity to geohelminths and their potential effects on non-parasite mucosal immune responses. Such effects are likely to be of public health importance in middle- and low-income countries where these parasites are endemic. There is a need for human studies on the effects of geohelminth infections on mucosal immunity and the potential for anthelmintic treatment to modify these effects. Such studies are likely to provide important insights into the regulation of mucosal immunity and inflammation, and the development of more effective mucosal vaccines.

Airway hyperresponsiveness is associated with activated CD4+ T cells in the airways

It is widely accepted that atopic asthma depends on an allergic response in the airway, yet the immune mechanisms that underlie the development of airway hyperresponsiveness (AHR) are poorly understood. Mouse models of asthma have been developed to study the pathobiology of this disease, but there is considerable strain variation in the induction of allergic disease and AHR. The aim of this study was to compare the development of AHR in BALB/c, 129/Sv, and C57BL/6 mice after sensitization and challenge with ovalbumin (OVA). AHR to methacholine was measured using a modification of the forced oscillation technique in anesthetized, tracheostomized mice to distinguish between airway and parenchymal responses. Whereas all strains showed signs of allergic sensitization, BALB/c was the only strain to develop AHR, which was associated with the highest number of activated (CD69(+)) CD4(+) T cells in the airway wall and the highest levels of circulating OVA-specific IgG(1). AHR did not correlate with total or antigen-specific IgE. We assessed the relative contribution of CD4(+) T cells and specific IgG(1) to the development of AHR in BALB/c mice using adoptive transfer of OVA-specific CD4(+) T cells from DO11.10 mice. AHR developed in these mice in a progressive fashion following multiple OVA challenges. There was no evidence that antigen-specific antibody had a synergistic effect in this model, and we concluded that the number of antigen-specific T cells activated and recruited to the airway wall was crucial for development of AHR.