Clinical approaches towards asthma and chronic obstructive pulmonary disease based on the heterogeneity of disease pathogenesis.

Asthma and chronic obstructive pulmonary disease (COPD) are each heterogeneous disease classifications that include several clinical and pathophysiological phenotypes. This heterogeneity complicates characterization of each disease and, in some cases, hinders the selection of appropriate treatment. Therefore, in recent years, emphasis has been placed on improving our understanding of the various phenotypes of asthma and of COPD and identifying biomarkers for each phenotype. Likewise, the concept of the endotype has been gaining acceptance; an endotype is a disease subtype that is defined by unique or distinctive functional or pathophysiological mechanisms. Endotypes of asthma or COPD may be primarily characterized by increased susceptibility to type 2 inflammation, increased susceptibility to viral infections, bacterial colonization or impaired lung development. The 'Dutch hypothesis' is as follows: gene variants underlying particular endotypes interact with detrimental environmental stimuli (e.g. smoking, viral infection and air pollution) and contribute to the ultimate development of asthma, COPD or both. Novel approaches that involve multidimensional assessment should facilitate identification and management of the components that generate this heterogeneity. Ultimately, patients with chronic inflammatory lung diseases may be treated based on these endotypes as determined by the respective biomarkers that correspond to individual endotypes instead of on disease labels such as asthma, COPD or even asthma-COPD overlap syndrome (ACOS).

Developments in the field of allergy in 2014 through the eyes of Clinical and Experimental Allergy.

The pathogenesis of asthma continues to be a major topic of interest to our authors with reviews and original papers on the role of viruses, mechanisms of inflammation, biomarkers, and phenotypes of asthma being major topics. A number of papers described new treatments for asthma focusing on blocking the Th2 response reflecting the fact that two decades of work in this area is finally bearing fruit. The pathogenesis of chronic rhinosinusitis is a growing area of interest, but there has been less on the genetics of airways disease than in previous years possibly reflecting the degree of rigour (and therefore a smaller body of work), with which these sorts of studies are now being undertaken. There continues to be a wide range of papers dealing with mechanisms of allergic disease ranging from clinical-based studies to basic research and the use of in vivo animal models especially mice. As before, mechanisms and new approaches to immunotherapy are common themes. Several were published in the allergens section investigating modification of allergens to increase their effectiveness and reduce the risk of adverse events. Risk factors for allergic disease was a common theme in the epidemiology section and food allergy a common theme in clinical allergy with papers on the development of protocols to induce tolerance and attempts to find biomarkers to distinguish sensitization from allergic disease. This was another exciting year for the editors, and we hope the readers of the journal.

Genomewide association study identifies HAS2 as a novel susceptibility gene for adult asthma in a Japanese population.

BACKGROUND: It is increasingly clear that asthma is not a single disease, but a disorder with vast heterogeneity in pathogenesis, severity, and treatment response. To date, 30 genomewide association studies (GWASs) of asthma have been performed, including by our group. However, most gene variants identified so far confer relatively small increments in risk and explain only a small proportion of familial clustering. OBJECTIVE: To identify additional genetic determinants of susceptibility to asthma using a selected Japanese population with reduced tobacco smoking exposure. METHODS: We performed a GWAS by genotyping a total of 480 098 single-nucleotide polymorphisms (SNPs) for a Japanese cohort consisting of 734 healthy controls and 240 patients with asthma who had smoked for no more than 10 pack-years. The SNP with the strongest association was genotyped in two other independent Japanese cohorts consisting of a total of 531 healthy controls and 418 patients with asthma who had smoked for no more than 10 pack-years. For the hyaluronan synthase 2 (HAS2) gene, we investigated SNP-gene associations using an expression quantitative trait loci (eQTL) database and also analysed its gene expression profiles in 13 different normal tissues. RESULTS: In the discovery GWAS, a SNP located upstream of HAS2, rs7846389, showed the strongest statistical significance (P = 1.43 × 10(-7) ). In the two independent replication cohorts, rs7846389 was consistently associated with asthma (nominal P = 0.0152 and 0.0478 in the first and second replication cohorts, respectively). In the meta-analysis, association of rs7846389 with susceptibility to asthma reached the level of genomewide significance (P = 7.92 × 10(-9) ). This variant was strongly correlated with HAS2 mRNA expression. The strongest expression of the gene was detected in the lung. CONCLUSIONS: Our study identified HAS2 as a novel candidate gene for susceptibility to adult asthma.

Variants in the 17q21 asthma susceptibility locus are associated with allergic rhinitis in the Japanese population.

BACKGROUND: Allergic rhinitis (AR) is a very common disorder peaking in the teenage years that is mediated by hypersensitivity responses to environmental allergens. Although it is well established that the ORMDL3 locus at chromosome 17q21 is associated with susceptibility to bronchial asthma, the genetic influences of the polymorphisms of the locus in allergic rhinitis are unclear. OBJECTIVE: To examine whether the polymorphisms in the 17q21 asthma susceptibility locus are associated with allergic rhinitis in the Japanese population. METHODS: We performed linkage disequilibrium (LD) mapping of the locus using the HapMap database and conducted an association study of the locus with a total of 15 tag SNPs in two independent populations. We further evaluated correlations of genotypes with changes in expression of genes at the region in lymphoblastoid cell lines in the Japanese population and assessed the expression levels of the genes in nasal epithelium and various human tissues. RESULTS: We found a significant association between a total of five polymorphisms in the 17q21 asthma susceptibility locus, rs9303277, rs7216389, rs7224129, rs3744246, and rs4794820, and AR (minimum P(combined)  = 0.00074, rs4794820). The expression level of the ORMDL3 transcript was significantly correlated with the genotype of rs12150079, rs7216389, rs3744246, and rs4794820 with P < 0.01 (minimum P = 0.0058, rs7216389), and ORMDL3 mRNA was highly expressed in nasal epithelium. CONCLUSION: Genetic variants in the 17q21 asthma susceptibility locus are significantly associated with AR in the Japanese population.

The prevalence of rhinitis and its association with smoking and obesity in a nationwide survey of Japanese adults.

BACKGROUND: Rhinitis is a common disease, and its prevalence is increasing worldwide. Several studies have provided evidence of a strong association between asthma and rhinitis. Although smoking and obesity have been extensively analyzed as risk factors of asthma, associations with rhinitis are less clear. OBJECTIVE: The aims of our study were (i) to evaluate the prevalence of rhinitis using the European Community Respiratory Health Survey (ECRHS) questionnaire in Japanese adults and (ii) to evaluate the associations of smoking and body mass index (BMI) with rhinitis. METHODS: Following our study conducted in 2006-2007 to determine the prevalence of asthma using the ECRHS questionnaire, our present analysis evaluates the prevalence of rhinitis and its association with smoking and BMI in Japanese adults 20-79 years of age (N = 22819). We classified the subjects (20-44 or 45-79 years) into four groups as having (i) neither rhinitis nor asthma; (ii) rhinitis without asthma; (iii) asthma without rhinitis; or (iv) rhinitis with asthma. We then evaluated associations with smoking and BMI in each group. RESULTS: The overall age-adjusted prevalence of rhinitis was 35.1% in men and 39.3% in women. A higher prevalence was observed in the younger population than in the older population. Active smoking and obesity were positively associated with asthma without rhinitis. In contrast, particularly in the 20- to 44-year age-group, active smoking and obesity were negatively associated with rhinitis without asthma. CONCLUSION: The results of the present study suggest that smoking and obesity may have different effects on the development of rhinitis and asthma.

Interleukin-33 induces interleukin-17F in bronchial epithelial cells.

BACKGROUND: IL-33 is clearly expressed in the airway of patients with asthma, but its role in asthma has not yet been fully understood. IL-17F is also involved in the pathogenesis of asthma. However, the regulatory mechanisms of IL-17F expression remain to be defined. To further indentify the role of IL-33 in asthma, we investigated the expression of IL-17F by IL-33 in bronchial epithelial cells and its signaling mechanisms. METHODS: Bronchial epithelial cells were stimulated with IL-33. The levels of IL-17F expression were analyzed using real-time PCR and ELISA. Next, the involvement of ST2, MAP kinases, and mitogen- and stress-activated protein kinase1 (MSK1) was determined by Western blot analyses. Various kinase inhibitors and anti-ST2 neutralizing Abs were added to the culture to identify the key signaling events leading to the expression of IL-17F, in conjunction with the use of short interfering RNAs (siRNAs) targeting MSK1. RESULTS: IL-33 significantly induced IL-17F gene and protein expression. The receptor for IL-33, ST2, was expressed in bronchial epithelial cells. Among MAP kinases, IL-33 phosphorylated ERK1/2, but not p38MAPK and JNK. It was inhibited by the pretreatment of anti-ST2 neutralizing (blocking) Abs. MEK inhibitor significantly blocked IL-17F production. Moreover, IL-33 phosphorylated MSK1, and MEK inhibitor diminished its phosphorylation. Finally, MSK1 inhibitors and transfection of the siRNAs targeting MSK1 significantly blocked the IL-17F expression. CONCLUSIONS: IL-33 induces IL-17F via ST2-ERK1/2-MSK1 signaling pathway in bronchial epithelial cells. These data suggest that the IL-33/IL-17F axis is involved in allergic airway inflammation and may be a novel therapeutic target.

Blockade of cysteinyl leukotriene-1 receptors suppresses airway remodelling in mice overexpressing GATA-3.

BACKGROUND: We demonstrated previously that GATA-3 overexpression markedly enhanced allergen-induced airway inflammation and airway remodelling, including subepithelial fibrosis, and smooth muscle cell hyperplasia, in transgenic mice. OBJECTIVE: Because cysteinyl leukotrienes (cysLTs) have been shown to be involved in such structural changes, the effects of a specific cysLT1 receptor antagonist, montelukast, were evaluated in a mouse model of chronic asthma. METHODS: GATA-3-overexpressing mice and wild-type Balb/c mice were sensitized and repeatedly challenged by ovalbumin (OVA) or saline. The effects of montelukast on the development of airway remodelling were compared between the two mouse genotypes. RESULTS: CysLTs in the lung were increased after repeated allergen challenges, and significantly enhanced in GATA-3-overexpressing mice. The enhanced cysLT levels were accompanied by the development of eosinophilia, smooth muscle cell hyperplasia, and increased stromal cell-derived factor-1 gene expression with a small increase in pro-collagen gene expression in OVA-challenged GATA-3-overexpressing mice, but not in wild-type mice. Montelukast significantly decreased lung cysLT levels and inhibited the GATA-3-overexpression-related airway remodelling, potently preventing smooth muscle cell hyperplasia, but partially suppressed the increased pro-collagen gene expression and eosinophilic inflammation. Increases in the levels of IL-4, IL-5, IL-13, and eotaxin in bronchial lavage and TGF-ß gene expression in the lungs were induced by OVA in both mouse genotypes. Montelukast treatment also significantly reduced these levels to the levels seen after saline challenges in GATA-3-overexpressing mice. CONCLUSION: Montelukast efficaciously prevented airway inflammation and remodelling in a GATA-3-overexpression antigen challenge mouse model by decreasing the cysLT-driven Th2 cytokine cycle of amplification of airway pathologies.

Induction of insulin-like growth factor-I by interleukin-17F in bronchial epithelial cells.

BACKGROUND: Increased expression of IL-17F has been noted in the airway of asthmatic patients, but its role in asthma has not been fully elucidated. Insulin-like growth FACTOR-I (IGF-I) is known to be involved in airway remodelling and inflammation, while its regulatory mechanisms remain to be defined. OBJECTIVE: To further clarify the biological function of IL-17F, we investigated whether IL-17F is able to regulate the expression of IGF-I in bronchial epithelial cells. METHODS: Bronchial epithelial cells were stimulated with IL-17F in the presence or absence of T-helper type 2 cytokines. Various kinase inhibitors were added to the culture to identify the key signalling events leading to the expression of IGF-I, in conjunction with the use of short interfering RNAs (siRNAs) targeting mitogen- and stress-activated protein kinase (MSK) 1, p90 ribosomal S6 kinase (p90RSK), and cyclic AMP response element-binding protein (CREB). RESULTS: IL-17F significantly induced IGF-I gene and protein expression, and co-stimulation with IL-4 and IL-13 augmented its production. MAP kinase kinase (MEK) inhibitors and the Raf1 kinase inhibitor significantly inhibited IGF-I production, and the combination of PD98059 and Raf1 kinase inhibitor showed further inhibition. Overexpression of Raf1 and Ras dominant-negative mutants inhibited its expression. MSK1 inhibitors significantly blocked IL17F-induced IGF-I expression. Moreover, transfection of the siRNAs targeting MSK1, p90RSK, and CREB blocked its expression. CONCLUSIONS: In bronchial epithelial cells, IL-17F is able to induce the expression of IGF-I via the Raf1-MEK1/2-ERK1/2-MSK1/p90RSK-CREB pathway in vitro.

Osteopontin is involved in migration of eosinophils in asthma.

BACKGROUND: Osteopontin (OPN) is an extracellular matrix protein with a wide range of functions, and is involved in various inflammatory diseases. However, the role of OPN in eosinophilic airway inflammation is unclear. OBJECTIVE: To elucidate the role of OPN in eosinophilic airway inflammation. METHODS: OPN protein levels in induced sputum from asthmatic patients and healthy controls were measured. Eosinophil migration assays were performed in the presence or absence of OPN, a blocking antibody (Ab) recognizing its integrin-binding domain (2K1) and an anti-integrin alpha 4 Ab (P1H4). In the mouse asthma model, the levels of eosinophilia were examined in bronchoalveolar lavage fluids (BALFs) from ovalbumin (OVA)-sensitized and -challenged mice with or without administration of an Ab (M5) corresponding to human 2K1. RESULTS: Levels of OPN in induced sputum were significantly higher in asthmatic patients when compared with healthy controls. In addition, levels of OPN were correlated with the percentage of sputum eosinophils. OPN induced significant migration of human eosinophils and this effect was inhibited by 2K1 and P1H4. M5 significantly attenuated OVA-induced eosinophilia in BALFs. CONCLUSION: These results indicate that OPN plays a role in the migration of eosinophils into the airways and may be involved in the pathogenesis of asthma.

Beta-2 adrenergic receptor genetic polymorphisms and asthma.

Beta-2-Adrenergic receptors (beta(2)AR) participate in the physiologic responses of the lung, including bronchodilation and bronchoprotection, through mechanisms such as mucociliary clearance, fluid accumulation and mediator release from mast cells and basophils. Thus, these receptors may also play an important role in the pathophysiology of asthma. The gene encoding beta(2)AR (ADRB2) is extremely polymorphic, and studies of this gene improves our understanding of asthma and possibly lead to new methods to prevent, diagnose and treat it. This review summarizes results from various studies on the possible relationship of ADRB2 polymorphisms to asthma and asthma-related phenotypes, including bronchodilator responses to inhaled beta(2)-agonists. At present, it appears that, for asthma, ADRB2 polymorphisms are not aetiologically involved. However, they might affect disease severity and clinical response to both acute and chronic administration of beta(2)-agonists. The development is that by assessing the ADRB2 genotype, it might be possible to predict the clinical course of asthma as well as responsiveness to chronic administration of beta(2)-agonists. Carefully, performed and adequately powered clinical trials continue to be important for achieving those goals.

Functional single nucleotide polymorphisms of the CCL5 gene and nonemphysematous phenotype in COPD patients.

It was previously reported that the gain-of-function -28 guanine allele of the promoter single nucleotide polymorphism (SNP; cytosine to guanine substitution of nucleotide -28 (-28C>G)) in the CC chemokine ligand 5 gene (CCL5) was associated with susceptibility to late-onset asthma in patients who developed asthma at age > or =40 yrs. The clinical diagnosis of chronic obstructive pulmonary disease (COPD) includes emphysema and small airway disease, and upregulation of CCL5 has been described in the airways of patients with COPD. It was hypothesised that CCL5 has a genetic impact upon the variable expression of emphysema in patients with COPD. Patients with COPD were studied (n = 267). All of the patients underwent pulmonary high-resolution computed tomography (CT), and visual scoring (CT score) was performed to determine emphysema severity. Three SNPs of CCL5 were genotyped, including -403G>A, -28C>G and 375T>C. A significant difference was found in CT score according to CCL5 genotype; the -28G allele was inversely associated with CT score. When the analysis was confined to 180 patients with bronchial reversibility of <15%, even stronger evidence for this association was noted. Functional single nucleotide polymorphisms in the CC chemokine ligand 5 gene were associated with milder emphysema. Together with previous findings, the present study may identify the CC chemokine ligand 5 gene as part of a common pathway in the pathogenesis of late-onset asthma and chronic obstructive pulmonary disease with milder emphysema.

The gene polymorphism of tumor necrosis factor-beta, but not that of tumor necrosis factor-alpha, is associated with the prognosis of sarcoidosis.

OBJECTIVES: Few genetic markers for the prognosis of sarcoidosis have been found. Tumor necrosis factor (TNF)-alpha has been implicated in the pathogenesis of sarcoidosis. Induced TNF-alpha or TNF-beta levels have been shown to be associated with the polymorphisms of the TNF genes. We investigated the roles of such polymorphisms in the development and prolongation of sarcoidosis. SUBJECTS AND MEASUREMENTS: One hundred ten Japanese patients with sarcoidosis and 161 control subjects were genotyped for three biallelic polymorphisms in the promoter region of TNF-alpha gene by direct sequencing of polymerase chain reaction (PCR) products. A polymorphism of the TNF-beta gene (TNFB*1/TNFB*2) was detected by NCO: I restriction fragment length polymorphism analysis of PCR products spanning intron 1 and exon 2 of the TNF-beta gene. RESULTS: None of the polymorphisms conferred susceptibility to sarcoidosis. However, our study identified the allele TNFB*1, detected by the presence of a NCO: I restriction site, as a marker of prolonged clinical course, with the resolution of sarcoidosis being defined as the disappearance of all clinical symptoms, physical signs of active lesions, abnormal chest radiograph findings, and abnormal results of pulmonary function and biochemical tests. When the probability of remission in patients homozygous for TNFB*2 was defined as 1.00, it was 0.48 (95% confidence interval, 0.26 to 0.88; p < 0.05) in patients with TNFB*1 (genotypes TNFB*1/1 and TNFB*1/2). CONCLUSIONS: The TNFB*1 allele is a marker for prolonged clinical course in patients with sarcoidosis. Our study is the first to link a cytokine gene polymorphism to the prognosis of sarcoidosis.

Topoisomerase II alpha content and topoisomerase II catalytic activity cannot explain drug sensitivities to topoisomerase II inhibitors in lung cancer cell lines.

PURPOSE: Topoisomerase II alpha content, topoisomerase II catalytic activity and drug sensitivities to the topoisomerase II inhibitors, doxorubicin and etoposide, were examined in a panel of 14 unselected human lung cancer cell lines in order to determine the relationship between topoisomerase II and drug sensitivities to the topoisomerase II inhibitors. METHODS: Drug sensitivities were determined using a microculture tetrazolium assay. The topoisomerase II alpha levels were determined by Western blot analysis and the topoisomerase II catalytic activity was determined using a decatenation assay of kinetoplast DNA, using nuclear protein from cells of each cell line. RESULTS: Drug sensitivity tests revealed that small-cell lung cancer (SCLC) cell lines were more sensitive to drugs than non-small-cell lung cancer (NSCLC) cell lines. The relative topoisomerase II alpha levels and relative topoisomerase II catalytic activity from SCLC cell lines (mean +/- SD 0.89 +/- 0.54 and 5.3 +/- 3.4, respectively) were slightly higher than those from NSCLC cell lines (0.78 +/- 0.56 and 4.0 +/- 2.8, respectively), but the differences were not statistically significant, and not sufficient to account for the variation in drug sensitivities. Moreover, no clear association was observed between the topoisomerase II alpha levels or the topoisomerase II catalytic activity and drug sensitivities in the cell lines studied. CONCLUSIONS: These findings suggest that the difference in drug sensitivities to doxorubicin and etoposide in human lung cancer cell lines might not be explainable by the topoisomerase II alpha levels and topoisomerase II catalytic activity. Moreover, our results suggest that the topoisomerase II alpha levels and topoisomerase II catalytic activity may play a minor role in the determination of clinical drug resistance of human lung cancers.

A patient with chronic hepatitis C who simultaneously developed interstitial pneumonia, hemolytic anemia and cholestatic liver dysfunction after alpha-interferon administration.

Following a three-week administration of alpha-interferon (IFN-alpha), a 62-year-old woman with chronic hepatitis C manifested fever and dyspnea and showed diffuse infiltrative opacities on chest roentgenograms. Her laboratory data included results of anemia with reticulocytosis, a decreased complement level and hepatitis with elevated ALP, LDH and gamma-GTP. Because laboratory data also revealed a positive lymphocyte stimulation test for IFN-alpha, this cytokine was considered to be responsible for the development of interstitial pneumonia, hemolytic anemia and cholestatic liver dysfunction due to its immunomodulatory effects. Although these three disorders have been reported to develop singly after IFN-alpha therapy, this is the first report of a patient in whom these disorders occurred simultaneously.

[Genetic analysis of bronchial asthma in Japanese population--Fc epsilon RI beta gene and beta 2 adrenergic receptor gene].

Atopy and bronchial hyperresponsiveness are important elements for the development of bronchial asthma. On the basis of the progression of molecular biology, the genetic regulations of asthma are being examined extensively and, recently, the gene encoding a beta subunit of the high affinity receptor for IgE (Fc epsilon RI beta) and the gene encoding beta 2 adrenergic receptor (beta 2ADR) are considered to be responsible for asthma. The mutation in the Fc epsilon RI beta gene on chromosome 11q13 is reported to be associated with atopy in British families with maternal inheritance of atopy. However there is no such an association between atopy and 11q13 in Japanese families. The polymorphisms in the beta 2 adrenergic receptor gene are reported to be related to the degree of agonist promoted downregulation of the receptor, and these polymorphisms are found to affect the severity of asthma. There is also evidence which supports a relationship between the polymorphism of the receptor and airway hyperresponsiveness in Japanese families.

Molecular mechanisms for the regulation of Nrf2-mediated cell proliferation in non-small-cell lung cancers.

We previously demonstrated that the transcription factor NF-E2-related factor2 (Nrf2), expressed abundantly in non-small-cell lung cancer (NSCLC) cells, plays a pivotal role in the proliferation and chemoresistance of NSCLC. Here we show that Nrf2-mediated NSCLC cell proliferation is dually regulated by epidermal growth factor receptor (EGFR) signaling and an Nrf2 repressor protein Keap1 (Kelch-like ECH-associated protein-1). NSCLC cells expressing wild-type EGFR and Keap1 genes show enhanced proliferation on stimulation with EGFR ligand under non-stress conditions. Exposure to cigarette smoke extract (CSE) enhanced cell proliferation by modification of the Nrf2/Keap1 interaction. Although EGFR-tyrosine kinase inhibitor (TKI) inhibited the proliferation of these cells, exposure to CSE attenuated its efficacy. In NSCLC cells with Keap1 gene mutations, Nrf2 was constitutively activated owing to dysfunction of Keap1 and cells proliferated independently of EGFR signaling. Furthermore, EGFR-TKI was unable to inhibit their proliferation. In NSCLC cells with EGFR gene mutations, Nrf2 was constitutively activated by EGFR signaling. In these cells, proliferation was largely dependent on the EGFR signaling pathway. Although these cells were highly sensitive to EGFR-TKI, exposure to CSE or knockdown of Keap1 mRNA reduced sensitivity to EGFR-TKI. We found a case of NSCLC showing resistance to EGFR-TKI despite having EGFR-TKI-sensitive EGFR gene mutation because of dysfunctional mutation in Keap1 gene. Results indicate that oxidative stress reduces the anticancer effects of EGFR-TKI in wild-type Keap1 NSCLC cells. Analysis of Keap1 dysfunction may become a novel molecular marker to predict resistance to EGFR-TKI in NSCLC cells having EGFR-TKI-sensitive EGFR mutations. Finally, as the downstream molecule of both EGFR and Keap1 signaling, Nrf2 is an important molecular target for the treatment of NSCLC, where cells have mutations in EGFR, KRAS or Keap1 genes.

Role of interleukin-17F in chronic inflammatory and allergic lung disease.

IL-17 family members belong to a distinct category of cytokines that coordinate local tissue inflammation by inducing the release of pro-inflammatory and neutrophil-mobilizing cytokines. The importance of the IL-17 family in inflammatory and autoimmune disease is becoming increasingly apparent. IL-17F is a recently discovered member of the IL-17 family that has a number of biological activities through induction of various cytokines, chemokines, and mediators. IL-17A, the founding member of the IL-17 family, and IL-17F are produced by several inflammatory cells, including activated T cells, in response to infectious and antigenic stimuli. Overexpression of IL-17A or IL-17F in the lungs results in induction of CXC chemokines and neutrophil recruitment. In a case-control study of 1125 unrelated Japanese subjects, a His161 to Arg161 (H161R) substitution in the third exon of the IL17F gene was shown to be associated with asthma and chronic obstructive pulmonary disease (COPD). Functionally, this variant failed to induce cytokines and chemokines, and interestingly, was able to antagonize the activity of wild-type IL-17F. These results provide an experimental basis for the observed genetic association with chronic inflammatory lung diseases, and also suggest the potential therapeutic utility of this antagonistic variant of IL-17F. Given that asthma and COPD are complex diseases involving a number of genetic and environmental factors, the genetic impact of IL-17F H161R with regard to the development of chronic airway inflammation likely varies among individuals with different genetic backgrounds and environmental exposures.