The genetic basis of atopic asthma

Genetic Variants Associated with Bronchial Asthma Specific to the Population of the Russian Federation

Bronchial asthma (BA) is a disease that still lacks an exhaustive treatment protocol. In this regard, the global medical community pays special attention to the genetic prerequisites for the occurrence of this disease. Therefore, the search for the genetic polymorphisms underlying bronchial asthma has expanded considerably. As the present study progressed, a significant amount of scientific medical literature was analyzed and 167 genes reported to be associated with the development of bronchial asthma were identified. A group of participants (n = 7,303) who had voluntarily provided their biomaterial (venous blood) to be used in the research conducted by the Federal Medical Biological Agency of Russia was formed to subsequently perform a bioinformatic verification of known associations and search for new ones. This group of participants was divided into four cohorts, including two sex-distinct cohorts of individuals with a history of asthma and two sex-distinct cohorts of apparently healthy individuals. A search for polymorphisms was made in each cohort among the selected genes, and genetic variants were identified whose difference in occurrence in the different cohorts was statistically significant (significance level less than 0.0001). The study revealed 11 polymorphisms that affect the development of asthma: four genetic variants (rs869106717, rs1461555098, rs189649077, and rs1199362453), which are more common in men with bronchial asthma compared to apparently healthy men; five genetic variants (rs1923038536, rs181066119, rs143247175, rs140597386, and rs762042586), which are more common in women with bronchial asthma compared to apparently healthy women; and two genetic variants (rs1219244986 and rs2291651) that are rare in women with a history of asthma.

Relationship between various cytokines implicated in asthma

Asthma is a complex disorder involving immunologic, environmental, genetic and other factors. Today, asthma is the most common disease encountered in clinical medicine in both children and adults worldwide. Asthma is characterized by increased responsiveness of the tracheobronchial tree resulting in chronic swelling and inflammation of the airways recognized to be controlled by the T-helper 2 (Th2) lymphocytes, which secrete cytokines to increase the production of IgE by B cells. There are many cytokines implicated in the development of the chronic inflammatory processes that are often observed in asthma. Ultimately, these cytokines cause the release of mediators such as histamine and leukotrienes (LT), which in turn promote airway remodeling, bronchial hyperresponsiveness and bronchoconstriction. The CD4⁺ T-lymphocytes from the airways of asthmatics express a panel of cytokines that represent the Th2 cells. The knowledge derived from numerous experimental and clinical studies have allowed physicians and scientists to understand the normal functions of these cytokines and their roles in the pathogenesis of asthma. The main focus of this review is to accentuate the relationship between various cytokines implicated in human asthma. However, some key findings from animal models will be highlighted to support the discoveries from clinical studies.

Sensitivity to House Dust Mites Allergens with Atopic Asthma and Its Relationship with CD14 C(-159T) Polymorphism in Patients of West Bengal, India

India is the home to around 15-20 million asthmatics, and asthma prevalence is increasing in Indian metropolitan area, including Kolkata, West Bengal. Complex interactions of genetic and environmental factors are involved in asthma. Genome-wide search for susceptible loci regulating IgE response (atopy) have identified a candidate gene CD14 which is most important in the context of allergic responses of respiratory system. This study was aimed to investigate the role of house dust and house dust mites in development of bronchial asthma and to explore the possible association of candidate gene CD14 with disease manifestation among Kolkata patient population. Skin-prick test was done among 950 asthmatic patients against 8 aeroallergens, including house dust and house dust mites and total serum IgE and allergen-specific IgE were measured. Polymerase chain reaction-restriction fragment length polymorphism was done in patients and nonasthmatic control (n = 255 in each) to characterize a functional polymorphism, C(-159)T, of CD14, a positional candidate gene for allergy. We identified house dust as the most common aeroallergen sensitizer among atopic patients in Kolkata followed by Dermatophagoides pteronyssinus and Dermatophagoides farinae Hughes (Acari: Pyroglyphidae) mites. Patient's sera contain significantly higher IgE level than that of control. Allergen-specific IgE antibody test revealed that 76.36% patients had specific IgE antibody against D. pteronyssinus mite. There was a significant difference in the distribution of alleles and genotypes for CD14 polymorphism with an increase in disease severity. So, in Kolkata, house dust mite is a common aeroallergen and D. pteronyssinus is predominant among mites. The present study revealed that bronchial asthma has a genetic background.

Poly(ADP-Ribose)Polymerase-1 in Lung Inflammatory Disorders: A Review

Asthma, acute lung injury (ALI), and chronic obstructive pulmonary disease (COPD) are lung inflammatory disorders with a common outcome, that is, difficulty in breathing. Corticosteroids, a class of potent anti-inflammatory drugs, have shown less success in the treatment/management of these disorders, particularly ALI and COPD; thus, alternative therapies are needed. Poly(ADP-ribose)polymerases (PARPs) are the post-translational modifying enzymes with a primary role in DNA repair. During the last two decades, several studies have reported the critical role played by PARPs in a good of inflammatory disorders. In the current review, the studies that address the role of PARPs in asthma, ALI, and COPD have been discussed. Among the different members of the family, PARP-1 emerges as a key player in the orchestration of lung inflammation in asthma and ALI. In addition, PARP activation seems to be associated with the progression of COPD. Furthermore, PARP-14 seems to play a crucial role in asthma. STAT-6 and GATA-3 are reported to be central players in PARP-1-mediated eosinophilic inflammation in asthma. Interestingly, oxidative stress-PARP-1-NF-κB axis appears to be tightly linked with inflammatory response in all three-lung diseases despite their distinct pathophysiologies. The present review sheds light on PARP-1-regulated factors, which may be common or differential players in asthma/ALI/COPD and put forward our prospective for future studies.

Factors associated with asthma among under-fives in Mulago hospital, Kampala Uganda: a cross sectional study

BACKGROUND

Asthma is the most common chronic childhood illness, with rapidly increasing prevalence in low-income countries. Among young children, asthma is often under-diagnosed.We investigated the factors associated with asthma among under-fives presenting with acute respiratory symptoms at Mulago hospital, Uganda.

METHODS

A hospital-based cross sectional study of 614 children with cough and/or difficult breathing, and fast breathing, was conducted between August 2011 and June 2012. A questionnaire focusing on clinical history of the child was administered to the caretakers. A physical examination and, laboratory and radiological investigations were done. Asthma was defined according to GINA (Global Initiative for Asthma) guidelines which were modified by excluding the symptom of "chest tightness", spirometry/peak expiratory flow measurements and by adding chest x-ray findings to distinguish asthma from pneumonia. A panel of three paediatricians reviewed the participants' case reports and, guided by the study definitions, made a diagnosis of asthma or other. Multivariable logistic regression analysis was done to determine factors independently associated with asthma.

RESULTS

Of the 614 children, 128 (20.8%) had asthma, 125 (20.4%) bronchiolitis, 167 (27.2%) bacterial pneumonia only, 163 (26.5%) viral pneumonia while 31 (5.1%) had other diagnoses including pulmonary tuberculosis. The majority (71.1%) of children with asthma were aged ≥ 12 months. Factors associated with asthma included maternal asthma (AOR 2.4, 95% CI 1.2, 4.6), a history of allergy in the patient (AOR 2.6, 95% CI 1.2, 5.4,), use of gas for cooking (AOR 3.8, 95% CI 1.2, 13.3), prematurity (AOR 9.3, 95% CI 1.2, 83.3) and high level of education of caretaker (AOR 9.1, 95% CI 1.1, 72.8).

CONCLUSION

Maternal asthma, a history of allergy in the patient, use of gas for cooking, prematurity and high level of education of caretaker were significantly associated with asthma. There is need for studies to explore the role of the above factors in development and exacerbation of childhood asthma to provide information that can be used to design strategies for asthma prevention and control.

Antigen-induced airway hyperresponsiveness in absence of broncho-obstruction in sensitized guinea pigs

BACKGROUND

Airway obstruction after antigen challenge is not always observed in patients with allergic asthma, even if they develop hyperresponsiveness. A similar event is observed in our guinea pig model of allergic asthma. Our aim was to study this phenomenon.

METHODS

Sensitized guinea pigs were challenged with ovalbumin (OVA) 3 times every 10 days. Animals were divided into 2 groups: (1) Guinea pigs exhibiting airway obstruction after antigen challenge (R = responders), and (2) guinea pigs lacking airway obstruction response (NR = nonresponders). After the third antigen challenge, antigen-induced airway hyperresponsiveness (AI-AHR), serum OVA-specific immunoglobulins, bronchoalveolar lavage fluid (BALF) inflammatory cells, histamine, cysteinyl leukotrienes and thromboxane A2 (TxA2) BALF levels, and in vitro tracheal contraction induced by contractile mediators and OVA were evaluated.

RESULTS

R group consistently displayed a transient antigen-induced airway obstruction (AI-AO) as well as AI-AHR, high T×A2, histamine, OVA-IgG1, OVA-IgE and OVA-IgA levels, and intense granulocyte infiltration. NR group displayed no AI-AO and no changes in BALF measurements; nevertheless, AI-AHR and elevated OVA-IgG1 and OVA-IgA levels were observed. In all groups, histamine, TxA2 and leukotriene D4 induced a similar contraction. Tracheal OVA-induced contraction was observed only in R group. AI-AHR magnitude showed a direct association with OVA-IgG1 and OVA-IgA levels. The extent of AI-AO correlated directly with OVA-IgE and inversely with OVA-IgA levels.

CONCLUSIONS

Our data suggest that TxA2 and histamine participate in AI-AO likely through an IgE mechanism. AI-AHR might occur independently of AI-AO, contractile mediators release, and airway inflammatory cell infiltration, but IgA and IgG1 seem to be involved.

Asthma and Chronic Obstructive Pulmonary Disease (COPD) - Differences and Similarities

Bronchial asthma and COPD (chronic obstructive pulmonary disease) are obstructive pulmonary diseases that affected millions of people all over the world. Asthma is a serious global health problem with an estimated 300 million affected individuals. COPD is one of the major causes of chronic morbidity and mortality and one of the major public health problems worldwide. COPD is the fourth leading cause of death in the world and further increases in its prevalence and mortality can be predicted. Although asthma and COPD have many similarities, they also have many differences. They are two different diseases with differences in etiology, symptoms, type of airway inflammation, inflammatory cells, mediators, consequences of inflammation, response to therapy, course. Some similarities in airway inflammation in severe asthma and COPD and good response to combined therapy in both of these diseases suggest that they have some similar patophysiologic characteristics. The aim of this article is to show similarities and differences between these two diseases. Today asthma and COPD are not fully curable, not identified enough and not treated enough and the therapy is still developing. But in future better understanding of pathology, adequate identifying and treatment, may be and new drugs, will provide a much better quality of life, reduced morbidity and mortality of these patients.

Asthma and COPD - The C/EBP Connection

Asthma and chronic obstructive pulmonary disease (COPD) are the two most prominent chronic inflammatory lung diseases with increasing prevalence. Both diseases are associated with mild or severe remodeling of the airways. In this review, we postulate that the pathologies of asthma and COPD may result from inadequate responses and/or a deregulated balance of a group of cell differentiation regulating factors, the CCAAT/Enhancer Binding Proteins (C/EBPs). In addition, we will argue that the exposure to environmental factors, such as house dust mite and cigarette smoke, changes the response of C/EBPs and are different in diseased cells. These novel insights may lead to a better understanding of the etiology of the diseases and may provide new aspects for therapies.

Gene-environment interaction between interleukin-4 promoter and molds in childhood asthma

PURPOSE

To assess the role of gene-environment interaction between interleukin (IL)-4 promoter and mold exposure on the development of asthma.

METHODS

We conducted a cohort-based, incident, case-control study. The case group consisted of 188 children with new asthma and the control group (n = 376) was matched for age and gender. The outcome of interest was the development of asthma over the 6-year study period. The studied determinants were three polymorphisms of IL-4 promoter (TT, CT, and CC) and three indicators of exposure including histories of water damage, presence of visible molds, and perceived mold odor in the home.

RESULTS

Apparent joint effects between IL-4 promoter and mold exposure were observed on both additive and multiplicative scales. Specially, the risk of asthma was significantly associated with children carrying the CT genotype and visible mold exposure comparing with those carrying the TT genotype without any exposure indicator (adjusted odds ratio [OR], 2.14; 95% confidence interval [CI], 1.05-4.34; modified Rothman synergy index for directly use of odds and OR [s] = 1.41; P for interaction = .03). A similar tendency was found (s = 1.30; P for interaction = .04) for children who were exposed to mold odor and carried CT genotype (adjusted OR, 1.99; 95% CI, 1.03-4.41).

CONCLUSIONS

The results of this study suggest that gene-environment interactions between the IL-4 promoter and an indoor mold problem may play an important role in childhood asthma.

Mitochondrial genetic background plays a role in increasing risk to asthma

A number of studies suggest that mitochondrial dysfunction plays a role in the pathogenesis of asthma. To shed light for the first time on the role of the mitochondrial genome in the etiology of asthma we analyzed the mitochondrial tRNA genes and part of their flanking regions in patients with asthma compared with a set of healthy controls. We found a total of 10 mutations in 56 out of 76 asthmatic patients. Four of these mutations were not found in the control group, five were observed at a significantly lower frequency in controls, but none of the combinations of mutations detected in asthma patients was observed in the controls. Furthermore, we observed that 27.6% of the asthma patients (vs. 4% of the controls) belonged to the haplogroup U (Fisher test P = 0.00) and a positive significant correlation was found between the occurrence of the haplogroup U and the severity of the disease (Fisher test P = 0.02). Whereas further studies in larger cohorts are needed to confirm these observations we suggest that the mitochondrial genetic background plays a key role in asthma development.

Association of ADAM33 gene polymorphisms with asthma in a Chinese population

BACKGROUND AND AIM

Asthma is a very common disease involving genetic and environmental factors. A disintegrin and metalloproteinase 33 (ADAM33) has been one of the most exciting candidate genes for asthma since its first association with the disease in the white population. Recently, studies on the association of ADAM33 gene polymorphisms with the risk of asthma have been controversial. We therefore focused on testing the hypothesis that either single-nucleotide polymorphisms (SNPs) of the ADAM33 gene may be associated with asthma risk. The aim of this study was to evaluate the potential relationship between polymorphisms of ADAM33 and asthma in a Han population in China.

METHODS

A case control study was conducted in a Han population of eastern Chinese population. A total of 329 asthma patients and a control group of 316 healthy volunteers were recruited for this study. Four polymorphic sites (F+1, S2, T2 and V4) were selected for genotyping. Genotypes were determined by the allele-specific polymerase chain reaction with fluorescence melting curves and DNA sequencing method. Data were analysed using the chi-squared test software.

RESULTS

Statistically significant differences in the distributions of the S2 site between patients and controls were observed (χ2=7.140, P<0.05).

CONCLUSION

These preliminary results suggest an association between ADAM33 polymorphisms S2 C/G and asthma in a Chinese Han population. The SNPs (F+1 C/T, T2 G/A and V4 C/G) of the ADAM33 gene may be the causal variants in asthma disease, but the strength of this evidence is limited by our small sample size.

The Bcl I single nucleotide polymorphism of the human glucocorticoid receptor gene h-GR/NR3C1 promoter in patients with bronchial asthma: pilot study

Bcl I in the promoter polymorphism observed within h-GR/NR3C1 gene may play an important role in the development of bronchial asthma and resistance to GCs in the severe bronchial asthma. The aim of the investigation was to study the correlation between this h-GR/NR3C1 gene polymorphism and occurrence of asthma in the population of Polish asthmatics. Peripheral blood was obtained from 70 healthy volunteers and 59 asthma patients. Structuralized anamnesis, spirometry and allergy skin prick tests were performed in all participants. Genotyping was carried out with PCR–RFLP method. In healthy, non-atopic population variants of Bcl I: GG, GC, CC were found with frequency 0.129/0.471/0.400, respectively. In asthma patients Bcl I: GG, GC, CC occurred with respective frequencies of 0.410/0.462/0.128. Chi-square analysis revealed a significantly different (P < 0.05) distribution between cases and controls for the Bcl I polymorphism. The Bcl I polymorphism of h-GR/NR3C1 gene is significantly associated with bronchial asthma, susceptibility to the development of severe form and resistance to GCs in Polish population.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

Polymorphisms in IL13 pathway genes in asthma and chronic obstructive pulmonary disease

BACKGROUND

Asthma and chronic obstructive pulmonary disease (COPD) are chronic respiratory diseases involving an interaction between genetic and environmental factors. Interleukin-13 (IL13) has been suggested to have a role in both asthma and COPD. We investigated whether single nucleotide polymorphisms (SNPs) in the IL13 pathway may contribute to the susceptibility and severity of asthma and COPD in adults.

METHODS

Twelve SNPs in IL13 pathway genes -IL4, IL13, IL4RA, IL13RA1, IL13RA2 and STAT6- were genotyped in subjects with asthma (n = 299) and in subjects with COPD or healthy smokers (n = 992). Genetic association was evaluated using genotype and allele models for asthma severity, atopy phenotypes and COPD susceptibility. Linear regression was used to determine the effects of polymorphism on baseline lung function (FEV(1), FEV(1)/FVC).

RESULTS

In asthmatics, three IL13 SNPs - rs1881457(-1512), rs1800925(-1111) and rs20541(R130Q) - were associated with atopy risk. One SNP in IL4RA1 [rs1805010(I75V)] was associated with asthma severity, and several IL13 SNPs showed borderline significance. IL13 SNPs rs1881457(-1512) and rs1800925(-1111) were associated with better FEV(1) and FEV(1)/FVC in asthmatics. IL13 SNPs rs2066960(intron 1), rs20541(R130Q) and rs1295685(exon 4) were associated with COPD risk and lower baseline lung function in the recessive model. In females, but not in males, rs2250747 of the IL13RA1 gene was associated with COPD and lower FEV(1).

CONCLUSION

These data suggest that IL13 SNPs (promoter and coding region) and, to a lesser extent, IL4RA SNPs may contribute to atopy and asthma. We also provide tentative evidence that IL13 SNPs in the coding region may be of significance in COPD susceptibility.

The association forecasting of 13 variants within seven asthma susceptibility genes on 3 serum IgE groups in Taiwanese population by integrating of adaptive neuro-fuzzy inference system (ANFIS) and classification analysis methods

Asthma is one of the most common chronic diseases in children. It is caused by complicated coactions between various genetic factors and environmental allergens. The study aims to integrate the concept of implementing adaptive neuro-fuzzy inference system (ANFIS) and classification analysis methods for forecasting the association of asthma susceptibility genes on 3 serum IgE groups. The ANFIS model was trained and tested with data sets obtained from 425 asthmatic subjects and 483 non-asthma subjects from the Taiwanese population. We assessed 13 single-nucleotide polymorphisms (SNPs) in seven well-known asthma susceptibility genes; firstly, the proposed ANFIS model learned to reduce input features from the 13 SNPs. And secondly, the classification will be used to classify the serum IgE groups from the simulated SNPs results. The performance of the ANFIS model, classification accuracies and the results confirmed that the integration of ANFIS and classified analysis has potential in association discovery.

Oct-1 is responsible for the C-33T polymorphism effect in the IL-4 promoter

IL-4 is a pleiotropic immunoregulatory cytokine secreted by Th2 subset of CD4(+) Th cells. Several transcription factors (TFs) have been determined with various degrees of certainty to bind the IL-4 promoter and to regulate its expression in human. To investigate the mechanisms responsible for phenotypic effects of the C-33T IL-4 promoter polymorphism, we performed a search of TFs binding to this promoter locus and discriminating the -33C and -33T alleles. In silico searches suggest few factors bind this region. Using an electromobility shift assay we found that Jurkat T cells contained proteins which specifically interacted with oligonucleotide probes, corresponding to the -33 region. Considerable binding differences between C and T alleles were demonstrated using competitive conditions, the proteins bound predominantly with -33C allele. We found that the transcription factor Oct-1 produced the major shifted complex. The binding of Oct-1 was not improved using activated nuclear extracts; however, we observed increases in other shifted complexes upon cell activation. We suppose that Oct-1 occupancy may compete for binding of activator proteins to closely or overlapped binding sites. Our findings suggest that the interplay between Oct-1 and unknown TFs may be responsible for the C-33T polymorphism effects.

Immunotoxicologic analysis of maternal transmission of asthma risk

Asthma has origins in early life. Epidemiological studies show that maternal, more than paternal, asthma significantly increases a child's risk of developing the disease. Experimental animal models exist which reproduce the increased susceptibility to asthma seen in human studies, and allow analysis of immunotoxic mechanisms that may contribute to neonatal allergy. In addition to maternal asthma, chemically-induced skin contact hypersensitivity or exposure during pregnancy of non-allergic females to certain environmental agents, e.g., air pollution particles, can also result in increased susceptibility to asthma in their offspring. We review here experimental models of maternal transmission of asthma risk, the progress to date in identifying mechanisms, and potential directions for future research.

Toxocara seropositivity in Sri Lankan children with asthma

BACKGROUND

Toxocariasis occurs in humans due to infection with Toxocara canis or T. cati, the nematode parasites of dogs and cats, respectively. The relationship between toxocariasis and asthma is complex, with some studies demonstrating that children with asthma were more likely to be Toxocara seropositive as compared to non-asthmatic children, and other studies indicating no such significant relationship. The aim of the present study was to investigate Toxocara seropositivity and its association with asthma in a selected group of Sri Lankan children.

METHODS

Two groups of children were studied: group 1 included 100 children with confirmed bronchial asthma who were on regular inhaler steroid treatment for asthma; group 2 included 96 children who did not have physician-diagnosed asthma or upper respiratory tract infections, attending the same hospital. Diagnosis of Toxocara seropositivity was based on IgG Toxocara Microwell Serum Elisa Kits. Enzyme-linked immunosorbent assay was regarded as positive for a reading of 0.3 optical density units. Stool samples were examined for helminth ova.

RESULTS

Toxocara seropositivity in children with asthma was 29% and this was significantly more than Toxocara seropositivity among non-asthmatic children (P < 0.001). Toxocara seropositivity was identified as a significant risk factor of asthma in a univariate model. Eosinophilia was seen in a significantly higher proportion of non-asthmatic and asthmatic children who were Toxocara seropositive. Toxocara seropositivity, however, was not identified as a significant risk factor in a multivariate model.

CONCLUSIONS

The analysis confirmed previously identified risk factors for asthma but there was no association between the helminth parasitic infection, toxocariasis and bronchial asthma in children.

Detecting anti-FcepsilonRI autoantibodies in patients with asthma by flow cytometry

Autoimmune diseases have been implicated in the development of intrinsic asthma, however little data are available on the role of autoimmunity in the pathogenesis of asthma. The purpose of this study was to investigate circulating autoantibodies against the high-affinity receptor for immunoglobulin E, FcepsilonRI, in patients with asthma. Seventy-eight patients with asthma and 32 healthy control subjects were included. All individuals were tested using a triple-staining flow cytometry-based basophil activation test (BAT) for the potential presence of autoantibodies against FcepsilonRI. Of the 78 asthma patients, 29 (37.2%) had a positive BAT result, indicating that their serum was able to activate basophils, compared with only four (12.5%) of the control group, a statistically significant between-group difference. These data suggest that some asthma patients have aberrant anti-FcepsilonRI autoantibodies, which implies that autoimmunity may be one factor involved in the pathogenesis of intrinsic asthma.

An association study of 13 SNPs from seven candidate genes with pediatric asthma and a preliminary study for genetic testing by multiple variants in Taiwanese population

INTRODUCTION

Asthma is one of the most common chronic diseases in children. It is caused by complex interactions between various genetic factors and exposures to environmental allergens and irritants. Because of the heterogeneity of the disease and the genetic and cultural differences among different populations, a proper association study and genetic testing for asthma and susceptibility genes is difficult to perform.

MATERIALS AND METHODS

We assessed 13 single-nucleotide polymorphisms (SNPs) in seven well-known asthma susceptibility genes and looked for association with pediatric asthma using 449 asthmatic subjects and 512 non-asthma subjects in Taiwanese population.

RESULTS

CD14-159 C/T and MS4A2 Glu237Gly were identified to have difference in genotype/allele frequencies between the control group and asthma patients. Moreover, the genotype synergistic analysis showed that the co-contribution of two functional SNPs was riskier or more protective from asthma attack. Our study provided a genotype synergistic method for studying gene-gene interaction on polymorphism basis and genetic testing using multiple polymorphisms.

Duration of allergic susceptibility in maternal transmission of asthma risk

PROBLEM

Asthma has its origins in early-life. Maternal, not paternal asthma is an important risk factor, but the mechanisms and the duration of the maternal effect are unknown.

METHOD OF STUDY

Offspring of asthmatic and normal mice were sensitized with ovalbumin (OVA) at 1, 3, 6 and 10 weeks of age, challenged with aerosolized OVA 2 weeks later and tested for airway hyperresponsiveness (AHR) and allergic airway inflammation (AI).

RESULTS

Offspring of asthmatic, but not normal, mothers showed AHR and AI after OVA sensitization at week 1. Similarly increased susceptibility to OVA was observed when sensitized at 3 or 6 weeks, although the magnitude diminished. Offspring sensitized at 10 and challenged at 12 weeks showed some AI but no AHR.

CONCLUSION

In offspring from asthmatic mothers increased allergic susceptibility persisted through the young adulthood, albeit with gradual decline, which suggests a long-lived but reversible skewing of the developing immune system.

Toward a comprehensive set of asthma susceptibility genes

Epidemiological and twin studies have demonstrated that asthma is under genetic and environmental influences. Numerous candidate gene association studies as well as genome-wide linkage scans have followed, aiming to elucidate the genetic architecture underlying this complex disease. Several promising asthma susceptibility genes were identified, and a comprehensive catalogue of these genes seems a realistic goal within 5 to 10 years. However, a key challenge is to understand the combination of genes and environmental factors that gives rise to the disease in a specific individual. Currently, most of the reports of asthma susceptibility genes are either preliminary or controversial, with little knowledge about the genetic mechanisms leading to abnormal function of the gene that promotes the development of asthma. Replications of published associations are relatively few. Many factors, including the inherent complexity of asthma as well as methodological issues, can explain these inconsistencies. Promising genetic tools are emerging with the completion of the International HapMap Project that will increase the scope of gene-discovery investigations. It is hoped that these tools, combined with validation studies in additional populations, will enable the creation of a comprehensive catalogue of susceptibility genes for asthma. Notwithstanding the difficulties in making sense of the vast amount of new genetic data, we already see the emergence of new biological pathways of atopy, airway remodeling, and asthma that may lead to novel therapeutic approaches.

Correlation between asthma severity and serum IgE in asthmatic children sensitized to Dermatophagoides pteronyssinus

BACKGROUND

We undertook this study to test the possible correlation between serum concentration of total and specific IgE antibodies and asthma severity in asthmatic children sensitized to the house dust mite Dermatophagoides pteronyssinus.

METHODS

The study included 157 asthmatic children aged 5-15 years (8 +/- 3 years). Clinical diagnosis was based on personal and family history, physical examination, pulmonary function testing and skin tests. Asthma severity was determined according to GINA guidelines. In vitro tests included serum concentration of total and specific IgE.

RESULTS

All asthmatic children had elevated serum concentration of total IgE. The children with elevated serum concentration of total IgE also showed an increased serum concentration of specific IgE. Asthma of higher higher severity was present in patients with total IgE concentration >288.0 kIU/L (AUC = 0.736) and specific IgE to Dermatophagoides pteronyssinus >44.1 kIUA/L (AUC = 0.843). Intermittent asthma was present in 76.9% of children with specific IgE concentration <44.1 kIUA/L. The positive predictive value suggested with 79.2% probability that a child with a concentration of specific IgE to Dermatophagoides pteronyssinus >44.1 kIUA/L would have a more severe form of asthma.

CONCLUSIONS

Asthmatic children with higher asthma severity have a higher serum concentration of both total IgE (>288.0 kIU/L) and specific IgE to Dermatophagoides pteronyssinus (>44.1 kIUA/L), respectively.

Autologous serum skin test for autoantibodies is associated with airway hyperresponsiveness in patients with asthma

BACKGROUND

Autoimmune diseases have been implicated as a cause of intrinsic asthma; however, there is little data on the role of autoimmunity in the pathogenesis of asthma.

OBJECTIVE

The purpose of this study was to investigate circulating functional autoantibodies against the high-affinity IgE receptor FcepsilonRI or IgE in patients with asthma.

METHODS

Twenty-eight patients with asthma and 19 control subjects were included. All subjects were skin tested with autologous serum to assess for the potential presence of receptor FcepsilonRI or IgE autoantibodies. If the serum-induced wheal diameter was 1.5 mm larger than the histamine-induced wheal diameter and that was 3 mm larger than the saline-induced wheal diameter at 30 min, the reaction was defined positive.

RESULTS

Of the 47 total subjects (both asthma patients and control subjects), 13 (27.7%) had a positive autologous serum skin test (ASST). Of the 28 asthma patients, 8 (28.6%) were regarded as having autoimmune origin. Autoantibodies against FcepsilonRI or IgE were found in asthma patients, irrespective of atopic status (atopy+ 3/13 vs. atopy- 5/15). The wheal diameter related to ASST was not related to atopy. Asthma patients with ASST-positive results as compared with patients with ASST-negative results exhibited a significant increased airway hyperresponsiveness (PC(20) methacholine, 2.70 +/- 1.27 vs. 9.08 +/- 2.35; p < 0.026).

CONCLUSION

Our data demonstrate that aberrant autoantibodies against the high-affinity IgE receptor FcepsilonRI or IgE are related to airway hyperresponsiveness in patients with asthma.

The role of novel genes in modifying airway responses in asthma

Major progress has been made during the past few years in developing a better understanding of the genetic basis of asthma, which has led to the identification of several chromosomal regions and loci showing linkage to and association with asthma and asthma-related phenotypes. Recent positional cloning approaches have also been informative in identifying several strong candidate genes for asthma. As another approach, association studies between candidate gene polymorphisms and asthma-related phenotypes have been conducted in many areas and replicated in different ethnic groups. These approaches need to be followed by validation processes to confirm their functional relevance in the pathophysiology of asthma. In this review, we describe several novel genes, including ADAM33, ADRB2, and eotaxin, that modify airway responsiveness in asthmatic patients.

Allelic polymorphisms in the interleukin-4 promoter regions and their association with bronchial asthma among the Russian population

BACKGROUND

Susceptibility to the development of bronchial asthma (BA) and other atopic diseases is known to be associated with genetic components.

OBJECTIVE

To evaluate the possible role of the polymorphisms in IL-4 gene promoters (C-33T, C-590T and G-1098T) in modulating allergic response and asthma in the Russian population.

METHODS

The polymorphism analysis was carried out by PCR-RFLP; IL-4 and total IgE concentrations were determined by ELISA.

RESULTS

In the case group, the T allele was found at frequencies of 74% (C-33T), 51% (C-590T) and 5% (G-1098T); in the control group the frequencies were 22, 42 and 8%, respectively. Only the C-33T polymorphism was associated with BA. The concentrations of total IgE and serum IL-4 were raised in the case group, while in the control group they were normal. Serum IL-4 level depended on C-33T polymorphism both in the case and control groups, the mutant T allele promoting its increase. The dependence on C-590T polymorphism was detected only in the case group. As for the total IgE level, in both cases it depended on the polymorphism in the case group rather than the control. G-1098T polymorphism did not demonstrate any correlations with total IgE or serum IL-4 levels. All 3 polymorphisms did not affect the severity of BA in the case group. On the basis of the computer analysis, we propose that the T-33C region is the CREB-binding site.

CONCLUSIONS

Our data suggest that IL-4 promoter polymorphism in the Russian population might play a role both conferring susceptibility to BA and modulating the levels of serum IL-4 and total IgE.

IL-10 promoter and IL4-Ralpha gene SNPs are associated with immediate beta-lactam allergy in atopic women

BACKGROUND

Allergic reactions to beta-lactam antibiotics represent the most frequent cause of immunological drug reactions.

OBJECTIVE

This study evaluates the involvement of genetic susceptibility factors in patients with immediate allergic reactions to beta-lactams. We examined 15 single nucleotide polymorphisms (SNP) of genes coding proteins implicated in immunoglobulin (Ig)E synthesis regulation.

METHODS

We performed a case-control study involving 44 patients with immediate beta-lactam allergy and 44 control subjects, all matched for sex and atopy. Interleukin (IL)-4, IL-13, IL-4Ralpha, signal transducer and activator of transcription 6 (STAT6), interferon (IFN)-gammaR1, IFN-gammaR2 and FcepsilonRIbeta gene polymorphisms were determined using polymerase chain reaction (PCR) restriction fragment length polymorphism, and IL-21R gene and IL-10 promoter polymorphisms by direct sequencing.

RESULTS

Our analysis did not reveal differences in the distribution of the 15 SNPs between allergic patients and controls. However, among atopic subjects, we found two distinct significant associations between immediate beta-lactam allergy in women and the Ile75Val variant of IL-4Ralpha gene (P = 0.012, OR = 5.4, CI: 1.16-27.7), and two linked IL-10 promoter gene polymorphisms, -819C>T and -592 C>A (P = 0.023, OR = 17.5, CI: 1.26-533.07). In contrast, we observed no association in allergic male subjects in the atopic population. Interestingly, the IL-4Ralpha Ile75Val variant could have a paradoxal protective effect in atopic male patients (P = 0.004, OR = 0.07, CI: 0.01-0.66).

CONCLUSION

Our findings suggest that polymorphisms in the IL-10 promoter and IL-4Ralpha genes are genetic factors that favour beta-lactam immediate allergies in female patients with atopy.

Do biophysical properties of the airway smooth muscle in culture predict airway hyperresponsiveness?

Airway hyperresponsiveness is a cardinal feature of asthma but remains largely unexplained. In asthma, the key end-effector of acute airway narrowing is the airway smooth muscle (ASM) cell. Here we report novel biophysical properties of the ASM cell isolated from the relatively hyporesponsive Lewis rat versus the relatively hyperresponsive Fisher rat. We focused upon the ability of the cytoskeleton (CSK) of the ASM cell to stiffen, to generate contractile forces, and to remodel. We used optical magnetic twisting cytometry to measure cell stiffness and traction microscopy to measure contractile forces. To measure remodeling dynamics, we quantified spontaneous nanoscale motions of a microbead tightly anchored to the CSK. In response to a panel of contractile and relaxing agonists, Fisher ASM cells showed greater stiffening, bigger contractile forces, and faster CSK remodeling; they also exhibited higher effective temperature of the CSK matrix. These physical differences measured at the level of the single cell in vitro were consistent with strain-related differences in airway responsiveness in vivo. As such, comprehensive biophysical characterizations of CSK dynamics at the level of the cell in culture may provide novel perspectives on the ASM and its contributions to the excessive airway narrowing in asthma.

Clues to asthma pathogenesis from microarray expression studies

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR), tissue remodeling, and airflow obstruction. The pathogenesis of asthma is only partly understood, and there is an urgent need for improved therapeutic strategies for this disease. Microarray technology has considerable promise as a tool for discovery of novel asthma therapeutic targets, although the field is still in its infancy. A number of studies have described expression profiles derived from human asthmatic lung tissue, mouse airway tissue, or from key cell types associated with asthma, but to date relatively few studies have exploited these findings to discover new pathways involved in the pathogenesis of asthma. Among the genes to have been identified by array studies and validated by further studies are monokine induced by interferon (IFN)-gamma, fatty acid binding proteins (FABP), and complement factor 5 (C5). Here we provide examples of microarray approaches to the discovery of new molecules associated with asthma. We anticipate that these types of analyses will provide considerable insight into asthma pathogenesis and will provide a wealth of new molecules for downstream analyses such as gene deficient mouse studies, or monoclonal antibody production.

Atopy parameters in asthmatic children increase with accumulation of null-alleles of glutathione-S-transferase M1

Atopy parameters (total IgE, skin prick test, and peripheral blood eosinophil count) in children with atopic bronchial asthma depend on the number of glutathione-S-transferase M1 mutant alleles in the genotype and on family history of asthma.

ADAM33: a newly identified protease involved in airway remodelling

Asthma is a complex disorder in which major genetic and environmental factors interact to both initiate the disease and modify its progression. While asthma is recognised as a disorder of the conducting airways characterised by Th2-directed inflammation, it is being increasingly apparent that alteration of the structural cells of the airways (airway remodelling) is also fundamental to disease chronicity and severity. The gene ADAM33, encoding a novel member of a identified as an asthma susceptibility gene as the result of a positional cloning effort in a cohort of families recruited form the UK and USA. Subsequent genetic studies have now provided evidence that ADAM33 may be involved in determining lung function throughout life, associated with early life lung function as well as increased decline therapeutic intervention in asthma and future work will focus on the mechanisms by which it alters lung function and bronchial hyperresponsiveness.

Polymorphism of the mast cell chymase gene (CMA1) promoter region: lack of association with asthma but association with serum total immunoglobulin E levels in adult atopic dermatitis

BACKGROUND

Mast cell chymase has the potential to be an important mediator of inflammation and remodelling in the asthmatic lung. Previous studies have examined association between promoter polymorphism of the chymase gene (CMA1) and allergic phenotypes but the significance of this polymorphism is unclear. We have examined association of a CMA1 variant in relation to asthma in a large UK Caucasian family cohort.

METHODS

A polymorphism of the CMA1 gene promoter (-1903G/A) was genotyped in 341 asthmatic families and in 184 non-asthmatic adults recruited from the UK PCR-RFLP based genotyping. Association with asthma diagnosis, atopy, specific and total IgE, and atopy and asthma severity was examined.

RESULTS

Case-control studies did not reveal a significant difference in allele frequency between asthmatics and controls. A significant association was found between CMA1 genotypes and total IgE levels in subjects with self-reported eczema that remained significant after correction for multiple testing (median total serum IgE GG 297 kU/L, GA 144 kU/L, AA 48.4 kU/L, Pc=0.0032).

CONCLUSION

These data suggest that CMA1 promoter polymorphism does not contribute to asthma susceptibility or severity but may be involved in regulating IgE levels in patients with eczema.

Bronchospasm and its biophysical basis in airway smooth muscle

Airways hyperresponsiveness is a cardinal feature of asthma but remains unexplained. In asthma, the airway smooth muscle cell is the key end-effector of bronchospasm and acute airway narrowing, but in just the past five years our understanding of the relationship of responsiveness to muscle biophysics has dramatically changed. It has become well established, for example, that muscle length is equilibrated dynamically rather than statically, and that non-classical features of muscle biophysics come to the forefront, including unanticipated interactions between the muscle and its time-varying load, as well as the ability of the muscle cell to adapt rapidly to changes in its dynamic microenvironment. These newly discovered phenomena have been described empirically, but a mechanistic basis to explain them is only beginning to emerge.

Remodeling of the airway smooth muscle cell: are we built of glass?

Classical understanding of airway lumen narrowing in asthma has held that the isometric force generated by airway smooth muscle (ASM) must be at every instant in a static mechanical equilibrium with the external load against which the muscle has shortened. It has been established recently, however, that this balance of static forces does not apply in the setting of tidal loading as occurs during breathing and must give way to the broader concepts of (1). the perturbed contractile state that exists far from static equilibrium conditions and (2). mechanical plasticity of the ASM cell. Here we describe the hypothesis that the well-established static contractile state, the newly-elaborated perturbed contractile state, as well as the remarkable mechanical plasticity of the ASM cell, are all subsumed under a rubric that is at once surprising, unifying and mechanistic. The specific hypothesis suggested is that the ASM cell behaves as a glassy material [Phys. Rev. Lett. 87 (2001) 148102]. A glass is a material that has the disordered molecular state of a liquid and, at the same time, the rigidity of a solid. If the hypothesis is true, then the ability of the ASM cytoskeleton (CSK) to deform, to flow and to remodel would be determined by an effective temperature-called the noise temperature-representing the level of jostling (i.e. molecular noise or agitation) present in the intracellular microenvironment. The abilities of the CSK to deform, to flow and to reorganize represent basic biological processes that underlie a variety of higher cell functions. If supported by the data, therefore, this integrative hypothesis might have implications in medicine and biology that go beyond the immediate issues of smooth muscle shortening and its role in asthma.

Sex differences in heritability of sensitization to Blomia tropicalis in asthma using regression of offspring on midparent (ROMP) methods

A genetic basis for asthma- and atopy-related quantitative traits, such as allergen-specific immunoglobulin E (IgE) levels, has been suggested by the observed familial aggregation of these traits in temperate climates. Less information is available for tropical climates, where different allergens may predominate. Sensitivity to the mite Blomia tropicalis is related to asthma in tropical climates, but heritability of B. tropicalis sensitivity and the impact of age, sex, and other environmental covariates on heritability have not been widely explored. Total and specific IgE levels were measured by immunochemiluminescent assay in 481 members of 29 Barbadian families (comprised of 340 parent-offspring trios or pairs) ascertained through two asthmatic siblings. Trait heritability was estimated using regression of offspring on mid-parent (ROMP) and pairwise correlation analysis of unadjusted IgE levels and on residual values after adjustment for covariates. Heritability of IgE levels to the major antigen of B. tropicalis (Blo t M) estimated by ROMP in 180 complete parent-offspring trios was 0.56. Heritability was consistently greater for male offspring than for female offspring. Similar sex-specific patterns were observed for specific IgE to Dermatophagoides pteronyssinus and total IgE levels and were relatively unaffected by adjustment for covariates. Pairwise correlational analyses of specific and total IgE levels showed similar results. Moderate heritability of Blo t M IgE levels was detected in these Barbadian families and was greater for sons than daughters. Adjustment for covariates had minimal impact. This suggests that future investigations of genetic determinants of IgE levels should include approaches that allow for potential sex differences in their expression.

Polymorphisms in the interleukin-4 and interleukin-4 receptor alpha chain genes confer susceptibility to asthma and atopy in a Caucasian population

BACKGROUND

IL-4 by binding to its receptor (IL-4R) is essential for the development of airway inflammation present in asthma, through the induction of IgE synthesis in B cells and differentiation of T cells to a Th2 phenotype.

OBJECTIVE

To investigate the role of four common polymorphisms in the IL-4 (IL4-34CT and IL4-589CT) and IL-4Ralpha chain (IL4RAI50V and IL4RAQ576R) genes in conferring susceptibility to the development of atopy and/or asthma.

METHODS

Two polymorphisms in the IL-4 gene promoter, IL4-34CT and IL4-589CT, and two polymorphisms in the IL-4Ralpha chain gene, IL4RAI50V and IL4RAQ576R, have been genotyped using PCR-based methods in 341 asthmatic families and in 184 non-asthmatic adults recruited from the south of England.

RESULTS

Case-control analysis did not reveal differences in the distribution of the four polymorphisms between asthmatics and controls. However, the transmission disequilibrium test showed that the IL4-589 T allele was preferentially transmitted to asthmatic children (P=0.036) and that the IL4RAQ576 was preferentially transmitted to children with atopic asthma (P=0.018). Haplotype analysis showed a strong association between the IL4-34T/-589T haplotype and asthma per se (P=0.041), and a strong association between the IL4RA I50/Q576 haplotype and atopic asthma (P=0.006).

CONCLUSION

Our data suggest that polymorphisms in the IL-4 and IL-4Ralpha chain genes might play a role both conferring susceptibility to and modulating severity of atopy and asthma.

Genetic analyses in asthma: current concepts and future directions

Asthma is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Numerous loci and candidate genes have been reported to show linkage and association of asthma and the asthma-associated phenotypes, atopy, elevated immunoglobulin E (IgE) levels, and bronchial hyper-responsiveness to alleles of microsatellite markers and single nucleotide polymorphisms (SNPs) within specific cytokine/chemokine, and IgE regulating genes. While many studies reporting these observations are compelling, only one asthma gene conferring high risk has been mapped. In this review, we present studies that support linkage and/or associations to the various genetic loci and genes in asthma. The first genome-wide scan for linkage to quantitative traits underlying asthma identified linkage on chromosome 4q, 6, 7, 11q, 13q and 16. A genome scan in American families from three racial groups revealed linkage to chromosome 2q, 5q, 6p, 12q, 13q and 14q. A two-stage scan in Hutterite families from the US found linkage on chromosome 5q, 12q, 19q and 21q. A screen in German families identified linkage to asthma on chromosome 2q, 6p, 9 and 12q and a two-stage genome scan in French families found replicated linkage on chromosomes 1p, 12q and 17q. A study of asthma in Finland showed linkage to high IgE on 7q14. Apart from a European linkage study of 199 families with atopic dermatitis, which demonstrated significant linkage to chromosome 3q21, three other studies have reported linkage results of genome-wide significance, including a linkage study in 175 Icelandic asthma families (14q24), a study in 533 Chinese families with bronchial hyper-responsiveness (chromosome 2) and a study in 47 Japanese families with mite-sensitive atopic asthma (5q31), suggesting that these regions may harbor genes contributing to the development of asthma and allergies. While significant progress has been made in the field of asthma genetics in the past decade, the clinical implications of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype, remain undetermined.

A major susceptibility gene for asthma maps to chromosome 14q24

Asthma is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Numerous loci and candidate genes have been reported to show linkage and association to asthma and atopy. Although some studies reporting these observations are compelling, no gene has been mapped that confers a sufficiently high risk of asthma to meet the stringent criteria for genomewide significance. Using 175 extended Icelandic families that included 596 patients with asthma, we performed a genomewide scan with 976 microsatellite markers. The families were identified by cross-matching a list of patients with asthma from the Department of Allergy/Pulmonary Medicine of the National University Hospital of Iceland with a genealogy database of the entire Icelandic nation. We detected linkage of asthma to chromosome 14q24, with an allele-sharing LOD score of 2.66. After we increased the marker density within the locus to an average of one microsatellite every 0.2 cM, the LOD score rose to 4.00. We designate this locus "asthma locus one" (AS1). Taken together, these results provide evidence of a novel susceptibility gene for asthma on chromosome 14q24.

Cellular biomechanics in the lung

Mechanical forces affect both the function and phenotype of cells in the lung. In this symposium, recent studies were presented that examined several aspects of biomechanics in lung cells and their relationship to disease. Wound healing and recovery from injury in the airways involve epithelial cell spreading and migration on a substrate that undergoes cyclic mechanical deformation; enhanced green fluorescent protein-actin was used in a stable cell line to examine cytoskeletal changes in airway epithelial cells during wound healing. Eosinophils migrate into the airways during asthmatic attacks and can also be exposed to cyclic mechanical deformation; cyclic mechanical stretch caused a decrease in leukotriene C(4) synthesis that may be dependent on mechanotransduction mechanisms involving the production of reactive oxygen species. Recent studies have suggested that proinflammatory cytokines are increased in ventilator-induced lung injury and may be elevated by overdistention of the lung tissue; microarray analysis of human lung epithelial cells demonstrated that cyclic mechanical stretch alone profoundly affects gene expression. Finally, airway hyperresponsiveness is a basic feature of asthma, but the relationship between airway hyperresponsiveness and changes in airway smooth muscle (ASM) function remain unclear. New analysis of the behavior of the ASM cytoskeleton (CSK) suggests, however, that the CSK may behave as a glassy material and that glassy behavior may account for the extensive ASM plasticity and remodeling that contribute to airway hyperresponsiveness. Together, the presentations at this symposium demonstrated the remarkable and varied roles that mechanical forces may play in both normal lung physiology as well as pathophysiology.

Early life exposure to dietary and inhalant allergens

Increasing evidence points to early life, including fetal life, as being a critical time period during which the infant's allergic fate may be determined. However, initial antigen priming in utero necessitates fetal exposure to maternally derived allergen. This article reviews our current knowledge regarding materno-fetal allergen transfer in vivo and reflects on mechanisms by which this exposure might exert immunomodulatory influences on the developing immune system.

A genomewide search for quantitative-trait loci underlying asthma

A genomewide screen for quantitative-trait loci (QTLs) that underlie asthma was performed on 533 Chinese families with asthma, by the unified Haseman-Elston method. Nine asthma-related phenotypes were studied, including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), airway responsiveness as indicated by methacholine (MTCH)-challenge test, serum total immunoglobulin E (TIgE), serum-specific immunoglobulin E, eosinophil count in peripheral blood, and skin-prick tests with three different allergens (cockroach, Dermatophagoides pteronyssinus, and D. farinae). Our study showed significant linkage between airway responsiveness to MTCH and D2S1780 on chromosome 2 (P<.00002) and provided suggestive evidence (P<.002) for six additional possible QTLs: D10S1435 and D22S685, for FEV1; D16S412, for FVC; D19S433, for airway responsiveness to MTCH; D1S518, for TIgE; and D4S1647, for skin reactivity to cockroach. No significant or suggestive evidence of linkage for the other four traits was found.

Historical perspective on airway smooth muscle: the saga of a frustrated cell

Despite the lack of a clearly defined physiological function, airway smooth muscle receives substantial attention because of its involvement in the pathogenesis of asthma. Recent investigations have turned to the ways in which the muscle is influenced by its dynamic microenvironment. Ordinarily, airway smooth muscle presents little problem, even when maximally activated, because unending mechanical perturbations provided by spontaneous tidal breathing put airway smooth muscle in a perpetual state of "limbo," keeping its contractile machinery off balance and unable to achieve its force-generating potential. The dynamic microenvironment affects airway smooth muscle in at least two ways: by acute changes associated with disruption of myosin binding and by chronic changes associated with plastic restructuring of contractile and cytoskeletal filament organization. Plastic restructuring can occur when dynamic length changes occur between sequential contractile events or within a single contractile event. Impairment of these normal responses of airway smooth muscle to its dynamic environment may be implicated in airway hyperresponsiveness in asthma.

Current concepts on the genetics of asthma

Asthma is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having small effects. Numerous asthma and atopy loci have been reported in studies demonstrating associations and/or linkage of the asthma-associated phenotypes, atopy, elevated IgE levels, and bronchial hyperresponsiveness to alleles of microsatellite markers and single nucleotide polymorphisms within specific cytokine/chemokine and IgE regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. This review compiles the evidence that supports linkage and associations to the various genetic loci and candidate genes. Whereas significant progress has been made in the field of asthma genetics in the past decade, the roles of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype remain to be determined.

Use of transgenic animals to investigate drug hypersensitivity

Hypersensitivity reactions to drugs and environmental agents are often due to exaggerated humoral (Th(2)) or cell mediated (Th(1)) immune responses with typical cytokine profiles. Overexpression of Th(2) cytokines, such as IL-4, IL-5 or IL-13 in mice, enhances an IgE antibody mediated response, while deletion of these cytokines attenuates and/or prevents allergic responses. Conversely, modulation of Th(1) cytokine gene expression may affect cell-mediated immune responses. Therefore, cytokine transgenic mice are used as investigative tools to study potential chemicals and/or drug allergies. In addition to cytokines and chemokines, other factors are important for the development of allergic responses, such as IgE, Fc receptors, vasopressin and several other factors, which can be tested in transgenic mice.

Polymorphism of human mucin genes in chest disease: possible significance of MUC2

Most of the genes that encode epithelial mucins are highly polymorphic due to variations in the length of domains of tandemly repeated (TR) coding sequence, the part of the apomucin that is heavily glycosylated. We report here for the first time a difference in the distribution of MUC TR length alleles in chest disease. We examined the distribution of the length alleles of those MUC genes whose expression we have confirmed in the bronchial tree in an age- and sex-matched series of 50 pairs of atopic patients with and without asthma. There was no significant difference in the distribution of alleles of MUC1, MUC4, MUC5AC, and MUC5B. MUC2, however, showed a highly significant difference in distribution. The atopic, nonasthmatic individuals showed an allele distribution that was very different from all our other patient and control groups, this group showing a longer mean allele length. The observations suggest that longer MUC2 alleles may help protect atopic individuals from developing asthma, though the effect may be due to a linked gene. The biological significance of this variation with respect to susceptibility to asthma will merit further investigation, and it will also be important to substantiate this finding on an independent data set.