Linkage of high-affinity IgE receptor gene with bronchial hyperreactivity, even in absence of atopy

Associations between atopic markers in asthma and intestinal helminth infections in Cuban schoolchildren

Total serum IgE (tIgE), allergen-specific IgE (sIgE), and skin prick test (SPT) are commonly used markers for atopy and atopic disease. The association between these measures and their relationship to clinical symptoms differs in affluent and non-affluent countries. We investigated the role of intestinal helminth infections in observed variations in atopic markers and asthma, and possible diagnostic and epidemiological consequences. A cross-sectional study was conducted in Cuban schoolchildren (n = 1285; 4-14 yrs). Atopy was determined by SPT, sIgE, and tIgE; asthma by International Study of Asthma and Allergies in Childhood questionnaire; and intestinal helminth infections by stool examination. Percentages of tIgE, sIgE, and SPT positives were 88.9%, 25.5%, and 16.5%, respectively. Asthma was found in 20.8%, and helminth infections in 20.9% of the children. All three atopic markers were significantly associated with each other and with asthma. Median tIgE levels were higher in helminth-infected than in uninfected children, irrespective of their status of atopy/asthma. Discordant results between SPT and sIgE were observed in 22.6% of the children. Among SPT positives, 41% were sIgE negative. The proportion of SPT negatives among sIgE positives was 74% in helminth-infected and 58.4% in uninfected children (p < 0.05). Helminth infections affected tIgE levels, reconfirming the limited value of tIgE for diagnosis of atopy and asthma in tropical areas. Higher frequencies of sIgE than positive SPTs were observed, especially in helminth-infected children. This corresponds with current hypothesis on the role of helminths in atopy. However, the observed proportion of sIgE negatives among children with positive SPT suggests that other mechanisms may also be involved.

IgE immune complexes stimulate an increase in lung mast cell progenitors in a mouse model of allergic airway inflammation

Mast cell numbers and allergen specific IgE are increased in the lungs of patients with allergic asthma and this can be reproduced in mouse models. The increased number of mast cells is likely due to recruitment of mast cell progenitors that mature in situ. We hypothesized that formation of IgE immune complexes in the lungs of sensitized mice increase the migration of mast cell progenitors to this organ. To study this, a model of allergic airway inflammation where mice were immunized with ovalbumin (OVA) in alum twice followed by three daily intranasal challenges of either OVA coupled to trinitrophenyl (TNP) alone or as immune complexes with IgE-anti-TNP, was used. Mast cell progenitors were quantified by a limiting dilution assay. IgE immune complex challenge of sensitized mice elicited three times more mast cell progenitors per lung than challenge with the same dose of antigen alone. This dose of antigen challenge alone did not increase the levels of mast cell progenitors compared to unchallenged mice. IgE immune complex challenge of sensitized mice also enhanced the frequency of mast cell progenitors per 10(6) mononuclear cells by 2.1-fold. The enhancement of lung mast cell progenitors by IgE immune complex challenge was lost in FcRγ deficient mice but not in CD23 deficient mice. Our data show that IgE immune complex challenge enhances the number of mast cell progenitors in the lung through activation of an Fc receptor associated with the FcRγ chain. This most likely takes place via activation of FcεRI, although activation via FcγRIV or a combination of the two receptors cannot be excluded. IgE immune complex-mediated enhancement of lung MCp numbers is a new reason to target IgE in therapies against allergic asthma.

Characterization of the methylation patterns of MS4A2 in atopic cases and controls

BACKGROUND

It is largely unknown whether epigenetic modifications of key genes may contribute to the reported maternal effects in atopy. The aim of this study was to characterize the methylation patterns of the membrane-spanning 4-domains, subfamily A, member 2 gene (MS4A2) (beta-chain of the IgE high-affinity receptor), a key gene in the allergic cascade.

METHODS

Mass spectrometry and bisulphite sequencing were used to measure the methylation of two potential substrates for epigenetic regulation of MS4A2, namely a predicted promoter and a CpG-rich AluSp repeat. Methylation was measured in DNA extracted from peripheral blood lymphocytes of 38 atopic cases and 37 controls. Cases were positive for atopy, asthma, bronchial hyper-responsiveness and had high IgE levels. Both parents of eight atopic cases were also tested.

RESULTS

The AluSp element was highly methylated across all individuals (mean 0.92, range 0.87-0.94), a pattern inconsistent with classical imprinting. Variation in methylation at this locus was not associated with age, sex, daily steroid use or atopic status, and there were no differences in methylation between mothers and fathers of atopic cases. Bisulphite sequencing analysis of the promoter region showed that it was also not imprinted, and there was no evidence for allele-specific methylation, but we were unable to test for association with atopy status.

CONCLUSIONS

Methylation levels at the AluSp repeat analysed in MS4A2 were inconsistent with classical imprinting mechanisms and did not associate with atopy status. The promoter region was less methylated but further analysis of this region in larger cohorts is warranted to investigate its role in allergic disease.

A functional polymorphism (-603A --> G) in the tissue factor gene promoter is associated with adult-onset asthma

Tissue factor (TF) is important for initiation of coagulation and for the increased thrombin activity observed at sites of inflammation. Thrombin activity is induced by allergen challenge in asthmatic airways and is involved in the pathogenesis of asthma. A -603A --> G polymorphism (rs1361600) in the promoter region of the TF gene has been associated with serum TF levels and with the development of cardiovascular diseases. The aim of this study was to determine whether the functional -603A --> G polymorphism has genetic influences on the development of asthma. Case-control analysis was performed of the association between six common single-nucleotide polymorphisms (SNPs), including the -603A --> G polymorphism, at the TF gene, and the development of asthma, using two unrelated Japanese populations. In the primary population (n=826), the GG genotype at the -603A --> G polymorphism was associated with adult-onset asthma (onset at >or=21 years of age) (odds ratio (OR) 2.886, P=0.0231). A second population showed a similar tendency (n=1654, OR 1.602, P=0.064). Transcriptional activity of promoters with -603A --> G genotypes were examined using luciferase promoter assays. The -603G allele was associated with higher promoter activity (P<0.05). The association between the functional polymorphism (-603A --> G) in the TF gene promoter and adult-onset asthma indicates that TF is a candidate gene contributing to asthma susceptibility.

Provoked models of asthma: what have we learnt?

Asthma is a chronic inflammatory disease of the airways characterized by physiological abnormalities of variable airflow obstruction and airway hyperresponsiveness (AHR) to a wide variety of physical and inhaled chemical stimuli and the presence of symptoms. AHR is measured by challenging the airways with a variety of agonists and naturally occurring stimuli, which results in constriction of the airway smooth muscle, leading to airway narrowing and airflow limitation. There are two distinct mechanisms by which the airways can narrow to a constrictor stimulus and these are defined by the pathways they take to induce AHR. Direct stimuli are pharmacological agents administered exogenously (such as histamine or methacholine) that act 'directly' on specific receptors on the bronchial smooth muscle to cause constriction. The other mechanism by which the airway can narrow is via the inhalation of indirect stimuli, which include natural stimuli, such as allergen or exercise, and pharmacological agents such as adenosine monophosphate and hyper-osmotic agents (e.g. hypertonic saline or dry powder mannitol). These stimuli induce airway narrowing 'indirectly' by causing the endogenous release of mediators of bronchoconstriction from airway inflammatory cells. Provoked models of asthma have been extremely valuable in understanding the pathobiology of asthma, in aiding diagnosis, in helping to clarify the mechanisms of actions of effective drugs and in the development of new entities to treat asthma. Some provoked models are valuable clinically, particularly those that measure direct AHR, while others, particularly allergen challenge, have been used in animal models and in humans to study the mechanisms of allergen-induced airway inflammation and the associated physiological changes, as well in the development of new drugs for asthma. An emerging role for measurements of AHR is in the evaluation of the optimal treatment for patients with asthma.

IgE influences the number and function of mature mast cells, but not progenitor recruitment in allergic pulmonary inflammation

Studies performed using cultured cells indicate that IgE functions not only to trigger degranulation of mast cells following allergen exposure, but also to enhance their survival. Such an influence of IgE on mast cell homeostasis during allergic responses in vivo has not been established. In this study, we show that inhalation of Aspergillus fumigatus extract in mice induced a dramatic rise in IgE accompanied by an increase in airway mast cells. These had an activated phenotype with high levels of FcepsilonRI. Plasma mast cell protease-1 was also increased, indicating an elevated systemic mast cell load. In addition, enhanced levels of IL-5 and eosinophils were observed in the airway. Both mast cell expansion and activation were markedly attenuated in IgE(-/-) animals that are incapable of producing IgE in response to A. fumigatus. The recruitment of eosinophils to the airways was also reduced in IgE(-/-) mice. Analyses of potential cellular targets of IgE revealed that IgE Abs are not required for the induction of mast cell progenitors in response to allergen, but rather act by sustaining the survival of mature mast cells. Our results identify an important role for IgE Abs in promoting mast cell expansion during allergic responses in vivo.

Asthma genetics: personalizing medicine

Asthma is a chronic inflammatory lung disease that leads to significant morbidity, mortality, and economic burden. The clinical symptoms, which are a result of airway inflammation and reversible airway obstruction, have led to the mainstay of therapies for asthma: anti-inflammatory medications and bronchodilators. However, the efficacies of the various classes of medications are not equal among all patients and may be affected by asthma phenotypes, environmental exposures, and genetic differences. Similarly, the risk for developing asthma and the natural history of the disease show great inter-individual variability due to these same factors. Over the past few decades, much effort has been focused on the genetics of asthma, and investigators have identified more than one hundred potential asthma susceptibility genes, of which at least ten have been replicated in numerous independent studies. In parallel, researchers have also identified genetic factors that impact the pharmacotherapeutic responses to the major classes of asthma medications. While the results of previous studies have been promising, future investigations need to combine genetics, pharmacogenetics, accurate disease phenotyping, and environmental exposures to build the foundation for personalized and predictive medicine for the 21st century. The ultimate goal is to enable physicians to identify those at risk for asthma, intervene to prevent or attenuate the disease, and select the optimal medical regimen for each individual patient. If successful, the resulting paradigm shift in medical practice will lead to improved clinical outcomes and decreased health care expenditures.

Non-atopic asthma in children is related to maternal bronchial hyperreactivity

Data on the pathogenic mechanisms underlying the development of non-atopic asthma in children are scarce. Our aim was to evaluate the association and compare the atopic status, pulmonary functions, bronchial hyperresponsiveness and serum total immunoglobulin E (IgE) levels of parents of atopic and non-atopic asthmatic children by using objective methods. Fifty-one asthmatic children aged 4-16 yr and their parents were included into the study. Initially the American Thoracic Society's Respiratory Disease questionnaire inquiring data on symptoms of asthma, rhinitis and past medical history was filled in. Afterwards, skin prick test with aeroallergens, pulmonary function and methacholine bronchial provocation tests and serum sampling for total IgE level determinations were carried out. Bronchial hyperresponsiveness to methacholine was significantly more common in the mothers of non-atopic children compared to those of atopic ones, although no significant difference was observed in the skin prick test reactivity, pulmonary function test parameters and serum IgE levels. Questionnaire data revealed that the presence of asthmatic symptoms such as wheezing and phlegm and doctor-diagnosed asthma were more common in the mothers of non-atopic children. Meanwhile, asthmatic symptoms were also found to be significantly more common in fathers of non-atopic children. Logistic regression analyses revealed that maternal PC(20) was the only predictive factor for the risk of displaying non-allergic asthma in children. The results demonstrate that among the risk factors studied, maternal bronchial hyperreactivity was associated with the development of asthma in non-atopic children.

A critical review of the use of Clara cell secretory protein (CC16) as a biomarker of acute or chronic pulmonary effects

Biomarkers associated with asthma aetiology and exacerbation have been sought to shed light on this multifactorial disease. One candidate is the serum concentration of the Clara cell secretory protein (CC16, sometimes referred to as CC10 or uteroglobin). In this review, we examine serum CC16's relation to asthma aetiology and exacerbation. There is evidence that acute exposures to certain pulmonary irritants can cause a transient increase in serum CC16 levels, and limited evidence also suggests that a transient increase in serum CC16 levels can be caused by a localized pulmonary inflammation. Research also indicates that a transient increase in serum CC16 is not associated with measurable pulmonary damage or impairment of pulmonary function. The biological interpretation of chronic changes in serum CC16 is less clear. Changes in serum CC16 concentrations (either transient or chronic) are not specific to any one agent, disease state, or aetiology. This lack of specificity limits the use of serum CC16 as a biomarker of specific exposures. To date, many of the critical issues that must be understood before serum CC16 levels can have an application as a biomarker of effect or exposure have not been adequately addressed.

A polymorphism of MS4A2 (- 109T > C) encoding the beta-chain of the high-affinity immunoglobulin E receptor (FcepsilonR1beta) is associated with a susceptibility to aspirin-intolerant asthma

BACKGROUND AND OBJECTIVE

The MS4A2 gene, the beta chain of the high-affinity receptor for immunoglobulin (Ig)E, has previously been linked to atopy and asthma. The beta-chain of FcepsilonR1 enhances receptor maturation and signal transduction capacity, leading to the release of proinflammatory mediators and cytokines that can exacerbate the symptom of asthma. This study was performed to evaluate whether two genetic polymorphisms of the FcepsilonR1beta gene (FcepsilonR1beta-109T > C and FcepsilonR1beta E237G) are associated with aspirin-intolerant asthma (AIA). The MS4A2 gene polymorphisms (FcepsilonR1beta-109T > C and FcepsilonR1beta E237G) were determined by SNP-IT assays in patients with AIA (N = 164), aspirin-tolerant asthma (ATA, N = 144) and normal controls (NC, N = 264) recruited from a Korean population.

RESULTS

The genotype frequencies of FcepsilonR1beta-109T > C and E237G polymorphisms were not significantly associated with the pathogenesis of AIA. However, FcepsilonR1beta-109T > C polymorphism was significantly associated with the presence of specific IgE to Staphylococcal enterotoxin B (SEB); the number of subjects carrying both homozygous TT genotype of FcepsilonR1beta-109T > C and specific IgE to SEB was significantly higher in the AIA group when compared with the other control groups (P = 0.01, odds ratio (OR) = 7.723, 95% confidence interval (CI) = 1.327-39.860 for AIA vs. ATA; P = 0.02, OR = 6.364, 95% CI = 1.149 approximately 35.229 for AIA vs. NC). In addition, luciferase reporter assays also showed that the FcepsilonR1beta-109T allele was associated with higher promoter activity of MS4A2 in both RBL-2H3 and A549 cell lines.

CONCLUSION

FcepsilonR1beta-109T > C polymorphism may increase expression of MS4A2 by mast cells, leading to enhanced release of proinflammatory mediators in the asthmatic airway, contributing to increased susceptibility to AIA.

Factors responsible for differences between asymptomatic subjects and patients presenting an IgE sensitization to allergens. A GA2LEN project

The synthesis of allergen-specific IgE is required for the development of allergic diseases including allergic rhinitis and allergic asthma (patients), but many individuals with allergen-specific IgE do not develop symptoms (asymptomatic subjects). Differences may exist between asymptomatic subjects and patients. Whether the presence of allergen-specific IgE translates into clinical allergy most likely depends on a complex interplay of multiple factors. These include a family history of atopy, the levels of total serum IgE and, allergen-specific IgE or IgG, epitope-specificity of IgE and their degree of polyclonality (mono- vs polysensitized), as yet unidentified serum factors, the balance of T regulatory cells (Treg) and Th1/Th2 cells, the polymorphisms of the high affinity receptor for IgE (FcepsilonRI) and other factors regulating the activation of FcepsilonRI-bearing cells. Asymptomatic subjects may be more often monosensitized than patients who may be more often polysensitized. There are many unanswered important questions that need to be addressed in order to better understand how IgE sensitization translates into clinical allergy. The assessment of differences between the asymptomatic and symptomatic groups of subjects represent one of the scientific programs of Global Allergy and Asthma European Network funded by the European Union and the hypotheses underlying these differences are presented in this paper.

Gastrointestinal food allergy: new insights into pathophysiology and clinical perspectives

Adverse reactions to food that result in gastrointestinal symptoms are common in the general population; while only a minority of such individuals will have symptoms due to immunologic reactions to foods, gastrointestinal food allergies do exist in both children and adults. These immune reactions are mediated by immunoglobulin E-dependent and -independent mechanisms involving mast cells, eosinophils, and other immune cells, but the complexity of the underlying mechanisms of pathogenesis have yet to be fully defined. Knowledge of the spectrum of adverse reactions to foods that affect the digestive system, including gastrointestinal food allergy, is essential to correctly diagnose and manage the subset of patients with immunologically mediated adverse reactions to foods. Potentially fatal reactions to food necessitate careful instruction and monitoring on the part of health care workers involved in the care of individuals at risk of anaphylaxis. New methods of diagnosis and novel strategies for treatment, including immunologic modulation and the development of hypoallergenic foods, are exciting developments in the field of food allergy.

The cell cycle associated protein, HTm4, is expressed in differentiating cellsof the hematopoietic and central nervous system in mice

HTm4 is a member of a newly defined family of human and murine proteins, the MS4 (membrane-spanning four) protein group, which has a distinctive four-transmembrane structure. MS4 protein functions include roles as cell surface signaling receptors and intracellular adapter proteins. We have previously demonstrated that HTm4 regulates the function of the KAP phosphatase, a key regulator of cell cycle progression. In humans, the expression of HTm4 is largely restricted to cells of the hematopoietic lineage, possibly reflecting a causal role for this molecule in differentiation/proliferation of hematopoietic lineage cells. In this study, we show that, like the human homologue, murine HTm4 is also predominantly a hematopoietic protein with distinctive expression patterns in developing murine embryos and in adult animals. In addition, we observed that murine HTm4 is highly expressed in the developing and adult murine nervous system, suggesting a previously unrecognized role in central and peripheral nervous system development.

The role of the FcepsilonRI beta-chain in allergic diseases

The high affinity receptor for IgE, FcepsilonRI, is a multimeric surface receptor that is expressed exclusively as a tetramer on rodent cells, but exists as a tetramer or trimer on human cells. The tetrameric form is expressed on effector cells of allergic responses such as mast cells and basophils and is composed of an IgE-binding alpha-subunit, a beta-subunit and a gamma-subunit dimer. Complexes lacking the beta-subunit are found on human antigen-presenting cells. On mast cells and basophils, FcepsilonRI is essential for IgE-mediated acute allergic reactions. Crosslinking of FcepsilonRI by IgE and multivalent antigen induces a signaling cascade that culminates in the release of preformed mediators and the synthesis of lipid mediators and cytokines. The beta-subunit functions as an amplifier of FcepsilonRI expression and signaling. As a consequence, strongly enhanced mast cell effector functions and in vivo allergic reactions can be observed in the presence of FcepsilonRIbeta. In contrast, a truncated beta-isoform (betaT) that is produced by alternative splicing acts as an inhibitor of FcepsilonRI surface expression. Thus, by producing two proteins with antagonistic functions, the FcepsilonRIbeta gene could serve as a potent regulator of allergic responses. In addition, the genomic region encompassing the beta-chain has been linked to atopy and a number of polymorphisms within the FcepsilonRIbeta gene are associated with various atopic diseases. It remains to be elucidated how these polymorphisms might affect the allergic phenotype. These functions of the beta-chain together with the described genetic linkages to atopy make it a candidate for a role in the pathophysiology of allergic diseases.

Asthmatic disease among urban preschoolers: an observational study

Asthma is of increasing concern especially in industrialized countries. This cross-sectional study was to assess the influence of spatial and temporal variations in the urban air pollution profile on asthmatic disease. The prevalences presented are based on physician-diagnosed asthmatic and allergic disease data, collected between 1993 and 1995. Seven hundred and thirty-six preschool children (age 2 to 7, mean 5.7 years) of 37 daycare centres in the City of Leipzig participated in the study. Variations were observed in the lifetime prevalences of asthma and allergy with differences in a residential area's ambient pollution profile. Depending on the level of traffic (high or low), children residing in areas with a dominant coal-heating emission profile had more frequently a diagnosis of asthma, 17.5% and 8.8% (95% confidence intervals [CI]: 10.8...23.5 and 5.8...11.6, respectively), as compared to those, living in centrally heated areas 13.4% and 5.8% (CI: 6.6...19.3 and 1.2...9.6, respectively). Allergic disorders occurred more often in areas with a predominantly traffic-associated pollution profile, 14.3% and 9.6% vs. 5.8% and 3.7% (CI: 7.4...20.3 and 6.4...12.5; 1.2...9.6 and 0.2...6.5, respectively). Interestingly, asthmatic disease was not necessarily associated with a clinical history of allergies. Of the children with physician-diagnosed asthma, 83.7% were not reported to have a concurrent diagnosis of allergies nor to show clinical symptoms. This suggests that environmental exposures (i.e., complex pollution mixtures associated with residential coal-heating and/or traffic) may have differentially influenced the phenotypic expression of asthma. A qualitative discussion is presented on the occurrence of "asthma without reported allergies" in Leipzig.

LD mapping of maternally and non-maternally derived alleles and atopy in FcepsilonRI-beta

Polymorphisms in the beta chain of the high affinity receptor for IgE (Fc epsilon RI-beta, MS4A2) are consistently associated with traits underlying asthma and atopy (immunoglobulin E-mediated allergy). However, the causal variants and haplotypes underlying disease have not yet been identified. Maternal effects, with association confined to maternally derived alleles, have been shown in some studies but not in others. We have therefore extended the known sequence and systematically detected polymorphisms across an 18.1 Kb genomic region that includes Fc epsilon RI-beta. Association testing in two panels of subjects showed the presence of single-nucleotide polymorphisms (SNPs) affecting prick skin tests and specific IgE responses in several clusters. Stepwise analyses indicated that the clusters represent independent effects. Interferon regulatory factor 2 (IRF-2) sites were altered by significantly associated SNPs in two regions. Strong association to maternally derived alleles was seen in one panel of subjects and not in the other. Maternal and non-maternally derived associations tended to share the same SNP clusters, but associations were stronger in the presence of maternal effects. Two regions of increased CpG concentration were identified in Fc epsilon RI-beta. One of these approximated a SNP cluster that showed strong association and maternal effects, providing a potential substrate for epigenetic effects.

Gene polymorphisms within the immune system that may underlie drug allergy

Drug allergy encompasses a broad spectrum of different diseases. It occurs in some individuals, whereas it does not occur in many others. This suggests, among others, the involvement of hereditary factors, and thus of gene polymorphisms. Since drug metabolising enzymes as well as the immune system itself may be responsible for drug allergy, gene polymorphisms are relevant in both systems. While already some information exists on gene polymorphisms of drug metabolising enzymes that result in drug allergy, little information is available on gene polymorphisms within the immune system that result in such allergy. This review sets out to provide an avenue for future research aimed at discovering such polymorphisms. To this end, immune mechanisms that underlie drug allergy will be discussed. A pivotal mechanism underlying several types of drug allergy, immediate-type (type I) hypersensitivity, is also a hallmark of asthma, and therefore drug allergy and asthma share a range of candidate genes. Research on asthma has come relatively far in establishing associations of disease with polymorphisms in these genes. Therefore, these polymorphisms and their associations with asthma will be discussed. These studies on asthma provide us with lessons on how to conduct such studies on drug allergy.

Regulation of the human high affinity IgE receptor beta-chain gene expression via an intronic element

The high affinity IgE receptor, FcepsilonRI, is a key regulatory molecule in the allergic reaction. By screening for cis-acting elements over the entire region of the human FcepsilonRI beta-chain gene, a sequence located in the fourth intron was revealed to serve as a repressor element. This element was recognized by a transcription factor, myeloid zinc finger protein 1 (MZF-1). Introduction of MZF-1 antisense inhibited the suppressive effect of the element on the beta-chain promoter and increased the mRNA for the beta-chain in KU812 cells, indicating that MZF-1 repressed human FcepsilonRI beta-chain gene expression via the element in the fourth intron. Furthermore, it was suggested that a cofactor binding with MZF-1, whose expression level was different among the cell types, was required for transcriptional repression by MZF-1.

Evidence for asthma susceptibility genes on chromosome 11 in an African-American population

Initial genome-wide scan data provided suggestive evidence for linkage of the asthma phenotype in African-American (AA), but not Caucasian, families to chromosome 11q markers (peak at D11S1985; LOD=2). To refine this region, mapping analysis of 91 AA families (51 multiplex families and 40 asthmatic case-parent trios) was performed with an additional 17 markers flanking the initial peak linkage marker. Multipoint analyses of the 51 multiplex families yielded significant evidence of linkage with a peak non-parametric linkage score of 4.38 at marker D11S1337 (map position 68.6 cM). Furthermore, family-based association and transmission disequilibrium tests conducted on all 91 families showed significant evidence of linkage in the presence of disequilibrium for several individual markers in this region. A putative susceptibility locus was estimated to be at map position 70.8 cM with a confidence interval spanning the linkage peak. Evidence from both linkage and association analyses suggest that this region of chromosome 11 contains one or more susceptibility genes for asthma in these AA families.

Competing functions encoded in the allergy-associated F(c)epsilonRIbeta gene

Allergic reactions are triggered via crosslinking of the high-affinity receptor for immunoglobulin E, F(c)epsilonRI. In humans, F(c)epsilonRI is expressed as a tetramer (alphabetagamma(2)) and a trimer (alphagamma(2)). The beta subunit is an amplifier of F(c)epsilonRI surface expression and signaling. Here, we show that as a consequence of alternative splicing, the F(c)epsilonRIbeta gene encodes two proteins with opposing and competing functions. One isoform is the full-length classical beta, the other a novel truncated form, beta(T). In contrast to beta, beta(T) prevents F(c)epsilonRI surface expression by inhibiting alpha chain maturation. Moreover, beta(T) competes with beta to control F(c)epsilonRI surface expression in vitro. We propose that the relative abundance of the products of the beta gene may control the level of F(c)epsilonRI surface expression and thereby influence susceptibility to allergic diseases.

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.

Airway hyperresponsiveness

Airway hyperresponsiveness is a characteristic feature of asthma and consists of an increased sensitivity of the airways to an inhaled constrictor agonist, a steeper slope of the dose-response curve, and a greater maximal response to the agonist. Measurements of airway responsiveness are useful in making a diagnosis of asthma, particularly in patients who have symptoms that are consistent with asthma and who have no evidence of airflow obstruction. These tests can be performed quickly, safely, and reproducibly. Certain inhaled stimuli, such as environmental allergens, increase airway inflammation and enhance airway hyperresponsiveness. These changes in airway hyperresponsiveness are of much smaller magnitude than those seen when asthmatic patients with persistent airway hyperresponsiveness are compared to healthy subjects. They are, however, similar to changes occurring in asthmatic patients that are associated with worsening asthma control. The mechanisms of the transient allergen-induced airway hyperresponsiveness are not likely to fully explain the underlying mechanisms of the persistent airway hyperresponsiveness in asthmatic patients.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

Genetics and genomics of asthma and allergic diseases

Asthma and eczema (atopic dermatitis) are characterized by a number of unexplained phenomena: the familial aggregation of disease, the initiation of disease by apparently trivial exposure to allergens, the preferential transmission of disease from affected mothers and the large increase in prevalence of disease in Westernized societies in the last century. A number of genes and chromosomal regions have been identified that consistently show linkage to asthma and its related phenotypes. Known loci modify the strength of the atopic response, nonspecific inflammation, the ability to respond to particular allergens and nonspecific airway reactivity. Eczema has been shown to be due to a different set of genetic loci that are shared with other skin diseases such as psoriasis and leprosy. Genetic and genomic studies both provide evidence that epithelial surfaces are active in the induction of allergic disease.

The genetics of atopic dermatitis

PURPOSE OF REVIEW

Atopic dermatitis is typified by itchy, inflamed skin. It is increasingly common in the developed world and is a major cause of morbidity in infants and young children. Most children with the disease have high levels of immunoglobulin E and many have concomitant asthma. The cause of the disease is unknown, but it is highly heritable. Identification of the genes and genetic variants underlying atopic dermatitis may lead to new treatments and better classification of children with the disease.

RECENT FINDINGS

Preliminary genetic studies have identified genes or clusters of genes that are expressed in the outermost layer of the skin to be just as important as genes that may modify the atopic process. These genes may influence other diseases, including psoriasis. Genome screens in mouse models seem to indicate involvement of some of the equivalent chromosomal regions as for human disease.

SUMMARY

The findings suggest that atopy in atopic dermatitis may be a secondary process, rather than the cause of the disease. The barrier function of the skin is seen not to be merely passive. Identification of the genes underlying atopic dermatitis is feasible and likely within a few years.

An association study between the Clara cell secretory protein CC16 A38G polymorphism and asthma phenotypes

BACKGROUND

Previously, an association has been reported between an increased risk of asthma and a polymorphism in the Clara cell secretory protein (CC16) gene [namely, an adenine to guanine substitution in the CC16 gene at position 38 (A38G) downstream from the transcription initiation site within the noncoding region of exon 1]. Homozygous individuals for the polymorphic sequence (AA genotype) were reported to have a significant (6.9 fold) increased risk of developing asthma. This finding has not been confirmed independently.

OBJECTIVE

To validate the association of CC16 A38G polymorphism to asthma in a separate well-characterized population through a case-control study.

METHODS

We conducted an association study using a sample of 217 unrelated Northern European Caucasians. Individuals were clinically characterized by a validated respiratory questionnaire, spirometry and bronchial reactivity measurement, and genotyped for the A38G polymorphism using PCR and restriction digestion. Association analysis was performed using the nonparametric Chi-squared tests.

RESULTS

In the unselected population, 43.3% participants were homozygous for the CC16*G allele and 45.4% were heterozygous (AG). We observed no significant difference in the distribution of positive bronchial reactivity to methacholine (at FEV1 PC20 of </= 8 mg/mL) across the three genotypes. Homozygous individuals for the CC16*A allele did not demonstrate an increased risk of asthma when compared to heterozygous or GG homozygotes. In addition, no significant difference was observed in the distribution of the CC16*A or *G alleles in the asthmatics vs. non-asthmatics.

CONCLUSION

CC16 polymorphism A38G does not influence the predisposition to asthma in this sample.

Polymorphism of the uteroglobin gene in systemic lupus erythematosus and IgA nephropathy

Uteroglobin (UG) is a multifunctional protein with anti-inflammatory/immunomodulatory properties. The UG gene is located on the long arm of chromosome 11 (11q12.3-q13.1) in a region linked to some immune disorders. A guanine-adenine substitution at position 38 (A38G) has been found in the noncoding region of exon 1 that is significantly correlated with an increased risk of developing immune-mediated diseases. Recently an experimental model of UG knockout mice showed that in mice, UG deficiency causes severe glomerulopathy with mesangial deposition of IgA-fibronectin complexes. To detect the presence of polymorphisms in the UG coding sequence, the DNA of 109 patients with IgA nephropathy (IgAN), and 32 patients with systemic lupus erythematosus (SLE) were tested for the nucleotide sequence of all three UG exons by heteroduplex analysis. We detected heterozygous DNA only for exon 1 due to the A38G substitution, as confirmed by sequencing. We tested for A38G polymorphism, by restriction endonuclease digestion (Sau96I), both in SLE patients and in IgAN patients. Twenty patients with either membranous nephropathy (12) or focal and segmental glomerular sclerosis and 120 healthy subjects served as controls. Compared with both healthy controls and non-IgA control patients, the frequency of the 38A allele was significantly higher in SLE patients (38 of 64 alleles versus 89 of 240 alleles, p = 0.002, and versus 7 of 40 alleles, p < 0.001). IgAN patients showed an allelic distribution similar to both control groups. A subgroup of 18 IgAN patients undergoing renal replacement therapy because of end-stage renal disease showed a significant increase in 38A allele frequency (5 of 36 38G alleles versus 31 of 36 38A alleles, p < 0.001). UG is an immunomodulatory agent that is able to (a) inhibit the activity of several phospholipase A2 (PLA2s), (b) interfere with the function of both neutrophils and monocytes, and (c) prevent immune recognition, perhaps by masking surface antigens. This could account for the role this molecule plays in SLE. The A38G polymorphism is located within a region corresponding to the rat minimal promoter that proved to be important in the transcriptional regulation of UG. Although the significance of any alterations in the UG exon 1 noncoding region in humans has yet to be clarified, initial evidence suggests that it may alter the control of immune response and of inflammation.

Asthma genetics

Asthma is the most common chronic childhood disease in developed nations and is a complex disease that has high social and economic costs. Asthma and its associated intermediate phenotypes are under a substantial degree of genetic control. Identifying the genes underlying asthma offers a means of better understanding its pathogenesis, with the promise of improving preventive strategies, diagnostic tools, and therapies. A number of chromosomal regions containing genes influencing asthma and atopy have been identified consistently by different groups, and a role for several candidate genes has been established.

Airway hyperresponsiveness and pulmonary function in adult asthma

BACKGROUND

Airway hyperresponsiveness (AHR) is a very important factor in the pathogenesis of bronchial asthma.

OBJECTIVES

To examine the relationship between airway obstruction and AHR in adult asthma.

METHODS

This study was a retrospective study in 161 adult asthmatic patients. Nonspecific AHR to methacholine was measured. We examined the correlations between AHR and pulmonary function, severity of asthma, type of asthma and age.

RESULTS

In the moderate and severe groups, peripheral airway obstruction was more aggravated compared to the mild group, and AHR was significantly more severe. Analysis of AHR by age showed that the degree of airway obstruction increased with aging, but age did not clearly correlate with airway sensitivity. Airway reactivity decreased with aging. Aspirin-induced asthma tended to be severe. In fatal asthma, central airway obstruction was significantly more severe. Although AHR in fatal asthma did not significantly differ from that in the severe group, airway sensitivity and airway reactivity tended to be increased.

CONCLUSIONS

AHR is an important factor determining the severity of asthma, and airway obstruction is an important index for the prediction of death from asthma. An evaluation of the degree of AHR and airway obstruction is considered to be the first step in controlling asthma.

Interactions between genes and environmental factors in asthma and atopy: new developments

Asthma and associated phenotypes are complex traits most probably caused by an interaction of multiple disease susceptibility genes and environmental factors. Major achievements have occurred in identifying chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma, atopic dermatitis, IgE levels and response to asthma therapy. The aims of this review are to explain the methodology of genetic studies of multifactorial diseases, to summarize chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma and associated traits, to list genetic alterations that may alter response to asthma therapy, and to outline genetic factors that may render individuals more susceptible to asthma and atopy due to environmental changes.

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.

Association study of proposed candidate genes/regions in a population of Spanish asthmatics

A number of genes/regions have recently been reported to be linked to asthma or its related phenotypes (i.e. atopy and bronchial hyperresponsiveness), by genetic linkage and allele-sharing methods. We have performed a case-control study comparing the allelic distribution of nine microsatellite markers and two genetic variants in a group of patients attended at emergency room departments because of an acute attack of asthma with respect to an external healthy population of controls. A total of 146 asthmatic subjects and 50 population controls from Barcelona, Spain, were genotyped for nine microsatellite markers from some asthma/atopy candidate genes/regions: the beta-subunit of the high-affinity IgE receptor (Fc epsilonRI-beta) located on chromosome 11; the 5q31-32 candidate region; the T-cell receptor genes, TCR-alpha on chromosome 14 and TCR-beta on chromosome 7. Two genetic variants of the beta-subunit of the high-affinity IgE receptor (Fc epsilonRI-beta) gene were also analyzed. None of the asthmatic or control individuals carried the Ile181Leu variant. There were no significant differences between asthmatic and control subjects neither for the polymorphic markers nor for the other variant of the beta-subunit of the high-affinity IgE receptor (Fc epsilonRI-beta) gene. No association could be observed in this sample of Spanish asthmatics with the genes/regions studied.

Murine models of inflammation: role of CD23

The role of IgE in eosinophil recruitment and bronchial hyperresponsiveness has been extensively studied with murine models of inflammation. Many investigators using various knockout models have clearly shown that both IgE-dependent and -independent pathways play a role in eosinophil recruitment and bronchial hyperresponsiveness after allergen challenge, illustrating the complexity of airways inflammation. The expression of this response is likely to involve many interacting pathways, and it will be a considerable challenge to determine key points within these pathways that will yield novel targets for future therapeutic strategies.

IL4-R1 (5q31-q33) and FcepsilonRI-betaca (11q13) markers and atopy: a case/control study in a spanish population

BACKGROUND

Rhinoconjunctivitis and bronchial asthma are atopic diseases with a high prevalence in the Canary Islands (Spain). Given that the most prevalent allergen is the house-dust mite Dermatophagoides pteronyssinus, early detection of genetically susceptible subjects would allow the application of preventive measures. The objective was to investigate the possible association of IL4-R1 (chromosome 5q31-q33) and FcepsilonRI-betaca (chromosome 11q13) markers with the atopic disease in our population.

METHODS

We performed a case/control study in which patients were recruited on the basis of diagnosis of rhinoconjunctivitis and/or bronchial asthma, and positive skin prick test to D. pteronyssinus. Analysis of IL4-R1 and FcepsilonRI-betaca microsatellites was carried out by PCR and electrophoresis in acrylamide gels.

RESULTS

We have not found evidence of association between IL4-R1 and FcepsilonRI-betaca markers and atopic disease in our population. In addition, these markers have shown a high percentage of homozygosis.

CONCLUSIONS

IL4-R1 and FcepsilonRI-betaca markers have not proved to be useful genetic markers for linkage or association studies in our population.

Development of bronchial hyperresponsiveness during childhood

Bronchial hyperresponsiveness (BHR) produces the characteristic pathological abnormalities seen in asthma and clearly plays a central role in the pathophysiology of asthma. The presence of BHR has been demonstrated in infants with asthma, as has the possibility of BHR persisting through the childhood period. The level of BHR may not only reflect the state of the airways, as a marker of airway dysfunction, but may also predict the persistent prognosis of the disease. Thus, measurement of BHR may provide important information about the symptoms and lung function in children with asthma. In view of multiple pathophysiological mechanisms, BHR does not seem to have a single cause. Many potential confounding variables, such as age, gender and genetic status, and some environmental factors, such as allergens, infections, and pollutants, could be responsible for the establishment of childhood BHR. There may be differences between the mechanisms that induce transient BHR and the mechanisms that induce persistent BHR. Also, there may be differences between the causes that induce BHR in the infantile period and the causes that maintain persistent BHR during childhood asthma. There is also disagreement as to the most suitable method to measure BHR in children, especially in infants. The assessment of BHR in young children has not been uniformly successful, and measurements of BHR changes over the childhood period (are associated with a number of problems. To resolve these problems, there may be two ways to study childhood BHR. One is to use age-matched specific techniques to clarify the precise BHR in each age group; the other is to use simple techniques that can be performed over the childhood period on a large number of subjects. In studies of infantile respirator, dysfunction the ultimate goal is to establish a simple, noninvasive method by which measurements of respiratory function may be obtained in infants. Further investigations and acceptable methods will be needed to clarify, the mechanisms involved in the establishment of asthma throughout the childhood period.

Using single nucleotide polymorphisms as a means to understanding the pathophysiology of asthma

Asthma is the most common chronic childhood disease in the developed nations, and is a complex disease that has high social and economic costs. Studies of the genetic etiology of asthma offer a way of improving our understanding of its pathogenesis, with the goal of improving preventive strategies, diagnostic tools, and therapies. Considerable effort and expense have been expended in attempts to detect specific polymorphisms in genetic loci contributing to asthma susceptibility. Concomitantly, the technology for detecting single nucleotide polymorphisms (SNPs) has undergone rapid development, extensive catalogues of SNPs across the genome have been constructed, and SNPs have been increasingly used as a method of investigating the genetic etiology of complex human diseases. This paper reviews both current and potential future contributions of SNPs to our understanding of asthma pathophysiology.

Evidence for genetic associations between asthma, atopy, and bronchial hyperresponsiveness: a study of 8- to 18-yr-old twins

We measured asthma in the last 12 mo, diagnosed by a respiratory physician at interview; atopy, defined by a positive skin prick test to any of eight common allergens; and bronchial hyperresponsiveness (BHR) to hypertonic saline, in 381 twin pairs aged 8 to 18 yr selected from the Australian Twin Registry-183 monozygous (MZ) and 198 dizygous (DZ). The associations between twins, as measured by an odds ratio, were greater in MZ pairs compared with DZ pairs for asthma: 25.6 (95% confidence interval 11.3- 57.8) versus 1.9 (1.0-3. 5); atopy: 14.6 (7.1-30.1) versus 2.5 (1.4- 4.5); and BHR: 14.1 (6. 4-31.0) versus 4.2 (2.1-8.6) (all p < 0.002). The associations between each pair of traits within an individual were slightly greater than the association between one trait in a twin and the other trait in the cotwin (cross-trait cross-pair) in MZ pairs. Further, the associations in MZ pairs were greater than in DZ pairs (p < 0.05). Under the assumptions of the classic twin model, these data suggest that the strong cross-sectional associations between these three traits are due to an overlap between the genetic factors involved in each of these three traits.

Mutation screening of interferon regulatory factor 1 gene (IRF-1) as a candidate gene for atopy/asthma

BACKGROUND

IL-4 gene cluster on chromosome 5 contains several candidate genes for atopy and asthma. Several independent studies have shown evidence for linkage between the markers flanking IL-4 gene cluster and asthma and/or asthma-related traits. Interferon regulatory factor 1 (IRF-1) is located approximately 300 kb telomeric to IL-4 and recent study reveals that IRF-1 deficiency results in an elevated production of Th2-related cytokines and a compensatory decrease in the expression of native cell- and Th1-related cytokines.

OBJECTIVE

To determine if there are any mutations associated with the development of atopy and asthma present in the coding exons and 5' flanking region of the IRF-1 gene.

METHODS AND RESULTS

We have screened the promoter and coding regions of the IRF-1 gene in atopic asthmatics and controls by SSCP method. We found three novel nuclear variants (the -300G/T and 4396 A/G polymorphisms and the 6355G > A rare variant) in the IRF-1 gene. No variants causing amino acid alterations of IRF-1 were detected. The -300G/T polymorphism was in nearly complete linkage disequilibrium with the 4396 A/G polymorphism. An association between the 4396 A > G polymorphism and atopy/asthma was examined by transmission disequilibrium test in 81 asthmatic families. Either of 4396 A or 4396G alleles was not significantly preferentially transmitted to atopy- or asthma-affected children.

CONCLUSION

The IRF-1 gene is less likely to play a substantial role in the development of atopy and asthma in the Japanese population.

Evidence for common genetic elements in allergic disease

Genetic research in allergic disease has focused primarily on asthma and its associated phenotypes (eg, total IgE), with very little attention given to the presence or absence of concomitant allergic diseases, especially allergic rhinitis and atopic dermatitis. Because asthma, allergic rhinitis, and atopic dermatitis share common systemic characteristics, it is reasonable to propose that a number of susceptibility genes could contribute to the allergic process regardless of the specific clinical phenotype. Consequently, the many genetic linkages previously reported for asthma may not be specific for asthma per se but rather may reflect an overall predisposition for allergic disease. Finally, epidemiologic data suggest that asthma and allergic rhinitis represent a continuum of disease, whereby those individuals with less severe disease will express rhinitis without asthma and those individuals with more severe disease express more than 1 phenotype. Alternatively, it is plausible that, in addition to the "allergic disease genes," there are "phenotype-specific genes" or possibly certain combinations of susceptibility genes (eg, gene-gene interactions) that contribute to the expression of asthma, allergic rhinitis, or atopic dermatitis.

Linkage analysis of markers on chromosome 11q13 with asthma and atopy in a United Kingdom population

Previous studies have suggested that atopy is linked to the beta chain of the high affinity IgE receptor (Fcepsilon R1-beta) on chromosome 11q13. Fcepsilon R1-beta polymorphisms, I181L, V183L, and E237G, are reported to be associated with asthma and atopy. The aim of this study was to investigate linkage to Fcepsilon R1-beta in a UK population and to assess the frequency of the polymorphisms and their association with asthma and atopy. A sample of 131 families was recruited at random with a sample of 109 families ascertained via an asthmatic proband. Each subject completed a written and video-assisted questionnaire and underwent bronchial challenge and skin prick testing. Serum total and specific IgE levels were measured. Quantitative scores were derived for asthma and atopy using principal component analysis. Four microsatellite markers were genotyped, including Fcepsilon R1-beta. The frequency of the I181L and V183L polymorphisms were determined by sequencing, and the E237G polymorphism was determined using the amplification refractory mutation system. We found no evidence for linkage to Fcepsilon R1-beta and only weak evidence for linkage to the less informative marker E237G. We found no examples of the I181L/V183L polymorphism in our population sample. Our study has failed to strengthen the evidence for a candidate gene on chromosome 11q13.

Allergy-associated polymorphisms of the Fc epsilon RI beta subunit do not impact its two amplification functions

Two variants of the beta-chain of the high affinity IgE receptor Fc epsilon RI, I181L-V183L and E237G, have been found associated with allergy. We have previously shown that the beta-chain plays at least two distinct amplifier functions. It amplifies Fc epsilon RI surface expression and signaling, resulting in an estimated 12- to 30-fold amplification of downstream events. To test the hypothesis that the I181L-V183L and E237G beta variants may be functionally relevant and could directly contribute to an allergic phenotype, we have evaluated the functional impact of the beta variants on the two amplifier functions of beta. We found that these variants have no direct effect on the beta amplifier functions. However, the possibility remains that these variants are in linkage disequilibrium with other more relevant polymorphisms or are affecting unknown beta-chain functions.

Genomic approaches to understanding asthma

Asthma is the most common chronic childhood disease in developed nations, and it is a complex disease that has high social and economic costs. Asthma and its associated intermediate phenotypes are under a substantial degree of genetic control. The genetic aetiology of asthma offers a means of better understanding its pathogenesis and, thus, improving preventive strategies, diagnostic tools, and therapies. Considerable effort and expense have been expended in attempts to detect genetic loci contributing to asthma susceptibility, and extensive candidate gene studies and a number of whole-genome screens have been undertaken. This article reviews the current state of knowledge of the genetics of asthma, with a focus on genomic approaches to understanding allergic diseases.

Childhood atopic asthma: positive association with a polymorphism of IL-4 receptor alpha gene but not with that of IL-4 promoter or Fc epsilon receptor I beta gene

We examined the relative contributions of three representative candidate genes for atopy (Fc epsilon receptor I beta, IL-4, and IL-4 receptor alpha) to the development of atopic asthma. Four polymorphisms of the three candidate genes including Ile50Val and Gln551Arg of IL-4 receptor alpha, -590C/T of IL-4 promoter and Glu237Gly of Fc epsilon receptor I beta were studied in 100 patients with atopic asthma and 100 nonatopic controls in the northern Kyushu area in Japan. Among the four polymorphisms of the three candidate genes, the Ile50 allele of the IL-4 receptor alpha chain gene demonstrated an association with atopic asthma subjects (p = 0.044), especially in patients with onset at 2 years of age or earlier (p = 0.034) and in patients with moderate to severe atopic asthma (p = 0. 031). Gln551Arg of IL-4 receptor alpha, -590C/T of IL-4 promoter and Glu237Gly of Fc epsilon receptor I beta showed no association with atopic asthma. A slight linkage disequilibrium between Ile50Val and Gln551Arg polymorphisms of the IL-4 receptor alpha chain gene was observed in both patients and nonatopic controls. The identification of additional atopy genes in areas with a certain genetic background is essential for genetic diagnosis and to establish new therapeutic modalities for atopic asthma.