Association between atopy and variants of the beta subunit of the high-affinity immunoglobulin E receptor

Lobelia chinensis Extract and Its Active Compound, Diosmetin, Improve Atopic Dermatitis by Reinforcing Skin Barrier Function through SPINK5/LEKTI Regulation

The skin acts as a mechanical barrier that protects the body from the exterior environment, and skin barrier function is attributed to the stratum corneum (SC), which is composed of keratinocytes and skin lipids. Skin barrier homeostasis is maintained by a delicate balance between the differentiation and exfoliation of keratinocytes, and keratinocyte desquamation is regulated by members of the serine protease kalikrein (KLK) family and their endogenous inhibitor SPINK5/LEKTI (serine protease inhibitor Kazal type 5/lympho-epithelial Kazal-type-related inhibitor). Furthermore, SPINK5/LEKTI deficiency is involved in impaired skin barrier function caused by KLK over-activation. We sought to determine whether increased SPINK5/LEKTI expression ameliorates atopic dermatitis (AD) by strengthening skin barrier function using the ethanol extract of Lobelia chinensis (LCE) and its active compound, diosmetin, by treating human keratinocytes with UVB and using a DNCB-induced murine model of atopic dermatitis. LCE or diosmetin dose-dependently increased the transcriptional activation of SPINK5 promoter and prevented DNCB-induced skin barrier damage by modulating events downstream of SPINK5, that is, KLK, PAR2 (protease activated receptor 2), and TSLP (thymic stromal lymphopoietin). LCE or diosmetin normalized immune response in DNCB treated SKH-1 hairless mice as determined by reductions in serum immunoglobulin E and interleukin-4 levels and numbers of lesion-infiltrating mast cells. Our results suggest that LCE and diosmetin are good candidates for the treatment of skin barrier-disrupting diseases such as Netherton syndrome or AD, and that they do so by regulating SPINK5/LEKTI.

Fc Receptor Variants and Disease: A Crucial Factor to Consider in the Antibody Therapeutics in Clinic

The fragment crystallizable (Fc) domain of antibodies is responsible for their protective function and long-lasting serum half-life via Fc-mediated effector function, transcytosis, and recycling through its interaction with Fc receptors (FcRs) expressed on various immune leukocytes, epithelial, and endothelial cells. Therefore, the Fc-FcRs interaction is a control point of both endogenous and therapeutic antibody function. There are a number of reported genetic variants of FcRs, which include polymorphisms in (i) extracellular domain of FcRs, which change their affinities to Fc domain of antibodies; (ii) both cytoplasmic and intracellular domain, which alters the extent of signal transduction; and (iii) the promoter region of the FcRs gene, which affects the expression level of FcRs, thus being associated with the pathogenesis of disease indications. In this review, we firstly describe the correlation between the genetic variants of FcRs and immunological disorders by individual differences in the extent of FcRs-mediated regulations. Secondly, we discuss the influence of the genetic variants of FcRs on the susceptibility to infectious diseases or cancer in the perspective of FcRs-induced effector functions. Overall, we concluded that the genetic variants of FcRs are one of the key elements in the design of antibody therapeutics due to their variety of clinical outcomes among individuals.

The tetraspan MS4A family in homeostasis, immunity, and disease

The membrane-spanning 4A (MS4A) family includes 18 members with a tetraspan structure in humans. They are differentially and selectively expressed in immunocompetent cells, such as B cells (CD20/MS4A1) and macrophages (MS4A4A), and associate with, and modulate the signaling activity of, different classes of immunoreceptor, including pattern recognition receptors (PRRs) and Ig receptors. Evidence from preclinical models and genetic evidence from humans suggest that members of the MS4A family have key roles in different pathological settings, including cancer, infectious diseases, and neurodegeneration. Therefore, MS4A family members might serve as candidate biomarkers and therapeutic targets for various conditions.

Role of montelukast in multitrigger wheezers attending chest clinic in Punjab, India

BACKGROUND

Wheeze is seen in 40% of preschool children, one-third of these may develop recurrent wheeze. Montelukast is an oral, once a day, easy to give therapy but there is no definite evidence to support its use in a recent meta-analysis. Present study was done to evaluate role of daily montelukast and various factors affecting the outcome after therapy in multitrigger wheeze (MTW).

METHODS

A prospective study conducted in Pediatric chest clinic over 18 months at DMCH, Ludhiana. Children from 6 months to 5 years, diagnosed cases of MTW were started on montelukast. Diagnosis based on symptoms of recurrent wheeze triggered by various allergens/precipitants was made by pediatrician in charge of chest clinic. Children were followed up at 1 and 3 months. They were labeled as controlled, partially controlled, or uncontrolled as per global initiative for asthma guidelines. Data were used to compare the outcome related to various factors.

RESULTS

Total 139 out of 150 children came for regular follow-up. At the end of 3 months, 94 (67.7%) were controlled, 8 (5.7%) partially controlled, and 37 (26.6%) children remained uncontrolled on montelukast. Factors associated with poor control were onset of symptoms at younger age (<6 months of age), family history of allergies, prior multiple visits or hospitalizations due to MTW, use of MDI in the past. No significant side effects were reported by parents.

CONCLUSION

Symptomatically two-third of children became better after starting montelukast. There were few factors which resulted in poorer control in subset of patients.

A hypermorphic antioxidant response element is associated with increased MS4A6A expression and Alzheimer's disease

Late onset Alzheimer's disease (AD) is a multifactorial disorder, with AD risk influenced by both environmental and genetic factors. Recent genome-wide association studies (GWAS) have identified genetic loci associated with increased risk of developing AD. The MS4A (membrane-spanning 4-domains subfamily A) gene cluster is one of the most significant loci associated with AD risk, and MS4A6A expression is correlated with AD pathology. We identified a single nucleotide polymorphism, rs667897, at the MS4A locus that creates an antioxidant response element and links MS4A6A expression to the stress responsive Cap-n-Collar (CNC) transcription factors NRF1 (encoded by NFE2L1) and NRF2 (encoded by NFE2L2). The risk allele of rs667897 generates a strong CNC binding sequence that is activated by proteostatic stress in an NRF1-dependent manner, and is associated with increased expression of the gene MS4A6A. Together, these findings suggest that the cytoprotective CNC regulatory network aberrantly activates MS4A6A expression and increases AD risk in a subset of the population.

Subcellular localization of MS4A13 isoform 2 in mouse spermatozoa

To identify upregulated genes during the development of spermatozoa, we performed PCR-selected subtraction analysis of testes RNA samples from 10-day-old and 12-week-old shrews. A transcript, highly homologous to two mouse transcripts, Ms4a13-1 and Ms4a13-2, was differentially regulated. Ms4a13-2, but not Ms4a13-1, was shown to be primarily expressed in mouse testes in an age-dependent manner. Ms4a13-2 cDNA contains an open-reading frame of 522 nucleotides, encoding a protein of 174 amino acids, with predicted molecular mass, 19,345 Da. MS4A13-2 protein was expressed along the periphery of nuclei of round and elongated spermatids (steps 3-16) in adult mouse testes, and in the equatorial region of the heads of fresh mature mouse spermatozoa. In addition, MS4A13-2 was found to localize to the outer acrosomal membrane in the equatorial region of heads in fresh spermatozoa. In acrosome-reacted spermatozoa, the MS4A13-2 expression extended to the entire sperm head including the postacrosomal region and acrosomal cap. MS4A family proteins are known to facilitate intracellular protein-protein interactions as ion channel/adaptor proteins by oligomerization, and have important regulatory roles in cellular growth, survival and activation. We report that the MS4A family member, MS4A13-2, may form oligomers in sperm membranes, which may be involved in an interaction with the zona pellucida or cumulus during fertilization.

Emerging concepts: mast cell involvement in allergic diseases

In a process known as overt degranulation, mast cells can release all at once a diverse array of products that are preformed and present within cytoplasmic granules. This occurs typically within seconds of stimulation by environmental factors and allergens. These potent, preformed mediators (ie, histamine, heparin, serotonin, and serine proteases) are responsible for the acute symptoms experienced in allergic conditions such as allergic conjunctivitis, allergic rhinitis, allergy-induced asthma, urticaria, and anaphylaxis. Yet, there is reason to believe that the actions of mast cells are important when they are not degranulating. Mast cells release preformed mediators and inflammatory cytokines for periods after degranulation and even without degranulating at all. Mast cells are consistently seen at sites of chronic inflammation, including nonallergic inflammation, where they have the ability to temper inflammatory processes and shape tissue morphology. Mast cells can trigger actions and chemotaxis in other important immune cells (eg, eosinophils and the newly discovered type 2 innate lymphocytes) that then make their own contributions to inflammation and disease. In this review, we will discuss the many known and theorized contributions of mast cells to allergic diseases, focusing on several prototypical allergic respiratory and skin conditions: asthma, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, allergic conjunctivitis, atopic dermatitis, and some of the more common medication hypersensitivity reactions. We discuss traditionally accepted roles that mast cells play in the pathogenesis of each of these conditions, but we also delve into new areas of discovery and research that challenge traditionally accepted paradigms.

Analysis of the conformation and thermal stability of the high-affinity IgE Fc receptor β chain polymorphic proteins

The high-affinity IgE Fc receptor (FcεRI) β chain acts as a signal amplifier through the immunoreceptor tyrosine-based activation motif in its C-terminal intracellular region. Polymorphisms in FcεRI β have been linked to atopy, asthma, and allergies. We investigated the secondary structure, conformation, and thermal stability of FcεRI β polymorphic (β-L172I, β-L174V, and β-E228G) proteins. Polymorphisms did not affect the secondary structure and conformation of FcεRI β. However, we calculated Gibbs free energy of unfolding (ΔGunf) and significant differences were observed in ΔGunf values between the wild-type FcεRI β (β-WT) and β-E228G. These results suggested that β-E228G affected the thermal stability of FcεRI β. The role of β-E228G in biological functions and its involvement in allergic reactions have not yet been elucidated in detail; therefore, differences in the thermal stability of β-E228G may affect the function of FcεRI β.

IgE FcɛR1β polymorphism and risk of developing chronic spontaneous urticaria: A study in an ethnic Kashmiri population

BACKGROUND

The pathogenesis of chronic spontaneous urticaria involves interplay between the genetic and environmental factors, most of which is still poorly understood. It is well-recognized that 30-40% of chronic spontaneous urticaria is autoimmune in nature. Chronic autoimmune urticaria is caused by anti-FcɛR1β and less frequently, by anti-IgE auto antibodies that lead to mast cell and basophil activation, thereby giving rise to the release of histamine and other proinflammatory mediators. We investigated the association between SNP loci in FcɛR1β and chronic spontaneous urticaria and to see its relation with serum IgE levels in Kashmiri population.

METHODS

The autologous serum skin test was used as a screening test for chronic autoimmune urticaria. PCR-RFLP was used to detect the genotype of the SNP loci. Serum IgE levels were assessed by ELISA kit.

RESULTS

No significant difference was found between the study population and control group in genotype distribution (wild and variant) among FcɛR1β loci (P value=0.06, odds ratio=0.29). The frequency of FcɛR1β (C109T) in autologous serum skin test positive chronic autoimmune urticaria patients with the CT genotype was found to be statistically non-significant when compared with the wild genotype (P=0.35). Carriers of FcɛR1β (T allele) had a more significant risk of developing CAU than those with C allele (P=0.01). In our population serum total IgE levels did not find any statistical significance with regard to ASST positive & ASST negative patients (P=0.26).

CONCLUSIONS

There is statistically no significant association between FcɛR1β gene polymorphism and CSU in Kashmiri population; however, there is a probability of developing CSU in patients carrying FcɛR1β T allele. Furthermore, serum total IgE levels had no significant association with the development of CAU.

Multifactor-dimensionality reduction reveals interaction of important gene variants involved in allergy

Elevated IgE levels in the atopic triad of asthma, allergic rhinitis and atopic dermatitis is a multifactorial condition whose genetic component involves interaction of several gene loci. One hundred and two matched pairs of allergic and nonallergic individuals were phenotyped for total serum IgE level using enzyme-linked immunosorbent assay (ELISA). Atopic status was defined by serum IgE concentration ≥100 IU mL(-1) . SNPs genotyped include the IL4 -590C>T (rs2243250), FCER1B E237G (rs569108), CD14 -159C>T (rs2569190), IL4RA Q551R (rs1801275) and ADRB2 R16G (rs1042713). Gene-gene interaction was analysed using multifactor-dimensionality reduction (MDR). Significant association between atopic allergy and the IL4 -590C>T polymorphism was confirmed in three genetic models. Interaction among the 5 gene variants was validated by MDR. The five-locus model was chosen as the best to describe the interaction of the SNPs within the context of atopy. The strongest interaction was between IL4 -590C>T and IL4RA Q551R and between FCER1B E237G and ADRB2 R16G. The IL4 variant also interacts synergistically with the FCER1B and ADRB2 coding variants. CD14 -159C>T, in general, interacts antagonistically with the rest of the SNPs. In conclusion, a five-locus interaction exists among IL4 -590C>T, FCER1B E237G, CD14 -159C>T, IL4RA Q551R and ADRB2 R16G in Filipino cases of atopic allergy.

The MS4A family: counting past 1, 2 and 3

The MS4A (membrane-spanning 4-domain family, subfamily A) family of proteins contains some well-known members including MS4A1 (CD20), MS4A2 (FcɛRIβ) and MS4A3 (HTm4). These three MS4A family members are expressed on the cell surface of specific leukocyte subsets and have been well characterized as having key roles in regulating cell activation, growth and development. However, beyond MS4A1-3 there are a large number of related molecules (18 to date in humans) where our understanding of their biological roles is at a relatively nascent stage. This review examines the larger MS4A family focusing on their structure, expression, regulation and characterized and/or emerging biological roles. Our own work on one family member MS4A8B, and its possible role in epithelial cell regulation, is also highlighted.

Maternal filaggrin mutations increase the risk of atopic dermatitis in children: an effect independent of mutation inheritance

Epidemiological studies suggest that allergy risk is preferentially transmitted through mothers. This can be due to genomic imprinting, where the phenotype effect of an allele depends on its parental origin, or due to maternal effects reflecting the maternal genome's influence on the child during prenatal development. Loss-of-function mutations in the filaggrin gene (FLG) cause skin barrier deficiency and strongly predispose to atopic dermatitis (AD). We investigated the 4 most prevalent European FLG mutations (c.2282del4, p.R501X, p.R2447X, and p.S3247X) in two samples including 759 and 450 AD families. We used the multinomial and maximum-likelihood approach implemented in the PREMIM/EMIM tool to model parent-of-origin effects. Beyond the known role of FLG inheritance in AD (R1_{meta-analysis} = 2.4, P = 1.0 x 10⁻³⁶), we observed a strong maternal FLG genotype effect that was consistent in both independent family sets and for all 4 mutations analysed. Overall, children of FLG-carrier mothers had a 1.5-fold increased AD risk (S1 = 1.50, P_{meta-analysis} = 8.4 x 10⁻⁸). Our data point to two independent and additive effects of FLG mutations: i) carrying a mutation and ii) having a mutation carrier mother. The maternal genotype effect was independent of mutation inheritance and can be seen as a non-genetic transmission of a genetic effect. The FLG maternal effect was observed only when mothers had allergic sensitization (elevated allergen-specific IgE antibody plasma levels), suggesting that FLG mutation-induced systemic immune responses in the mother may influence AD risk in the child. Notably, the maternal effect reported here was stronger than most common genetic risk factors for AD recently identified through genome-wide association studies (GWAS). Our study highlights the power of family-based studies in the identification of new etiological mechanisms and reveals, for the first time, a direct influence of the maternal genotype on the offspring’s susceptibility to a common human disease.

Most human diseases are caused by a combination of multiple environmental and genetic influences. The widely used case/control approach aims to identify disease risk genes by comparing the genetic constitution of affected and healthy individuals. Although successful, this approach ignores additional mechanisms influencing disease risk. Here, we studied mutations in the filaggrin gene (FLG), which are strong risk factors for atopic dermatitis (AD) and allergies, in a large number of families with AD. We found that FLG mutations in the mother, not the father, increased the AD risk of the children, even if the child did not inherit the mutation. Thus, our study revealed, for the first time, a direct influence of a maternal mutation on the child’s risk for a common disease. The maternal FLG effect was only found when the mothers were allergic, and was absent in families of non-allergic mothers. This finding suggests that FLG-induced changes in the maternal immune response shape the child’s immune system during pregnancy and increase the child’s risk for AD. Our study indicates that maternal FLG mutations act as strong environmental risk factors for the child and highlights the potential of family-based studies in uncovering novel disease mechanisms in medical genetics.

Mast cells, their subtypes, and relation to asthma phenotypes

Mast cells (MCs) are among the first cell types associated with allergies and asthma. Studies in human asthma have identified their presence in the lung submucosa and smooth muscle and also in the airway epithelium. As our understanding of the distribution and location of these MCs in the human airway has increased, it is clear that much remains to be understood regarding the presence and subtype of these MCs in relationship to asthma phenotypes, defined both clinically and on the basis of immunologic pathways. Human MCs have traditionally been divided into two major subtypes based on the protease granule content, with tryptase representing total MCs. There is emerging evidence that in the epithelium, MCs of an altered subtype (with tryptase, chymase, and/or carboxypeptidase A3) may play a role in the pathophysiology of poorly controlled, severe, Th2-associated asthma.

Molecular Mechanism of Allergy-Related Gene Regulation and Hematopoietic Cell Development by Transcription Factors

Transcriptional regulation for the genes encoding alpha- and beta-chains of the high-affinity receptor for IgE (FcepsilonRI) have been analyzed in mast cells and regulatory mechanisms are beginning to be elucidated. Transcription factors GATA-1 and PU.1 cooperatively transactivate the alpha-chain gene, and three transcription factors, GATA-1, Oct-1, and MZF-1, are involved in regulation of beta-chain gene expression. No single nucleotide polymorphisms (SNPs) that are functionally related to the allergic diseases have been identified in coding regions of the alpha- and beta-chain genes in a definitive way. However, recent studies on SNPs in the promoter regions have revealed that these genes are probable candidates for new types of allergy-related genes whose transcription levels are affected by transcription factors which discriminate SNPs in the promoters. Another interesting finding on transcription factors functioning in mast cells is that the expression level of PU.1 determines cell fate between mast cells and monocytes.

A truncated splice-variant of the FcεRIβ receptor subunit is critical for microtubule formation and degranulation in mast cells

Human linkage analyses have implicated the MS4A2-containing gene locus (encoding FcεRIβ) as a candidate for allergy susceptibility. We have identified a truncation of FcεRIβ (t-FcεRIβ) in humans that contains a putative calmodulin-binding domain and thus, we sought to identify the role of this variant in mast cell function. We determined that t-FcεRIβ is critical for microtubule formation and degranulation and that it may perform this function by trafficking adaptor molecules and kinases to the pericentrosomal and Golgi region in response to Ca2+ signals. Mutagenesis studies suggest that calmodulin binding to t-FcεRIβ in the presence of Ca2+ could be critical for t-FcεRIβ function. In addition, gene targeting of t-FcεRIβ attenuated microtubule formation, degranulation, and IL-8 production downstream of Ca2+ signals. Therefore, t-FcεRIβ mediates Ca2+ -dependent microtubule formation, which promotes degranulation and cytokine release. Because t-FcεRIβ has this critical function, it represents a therapeutic target for the downregulation of allergic inflammation.

Identifying genetic susceptibility to sensitization to cephalosporins in health care workers

Exposure to cephalosporins could cause occupational allergic diseases in health care workers (HCWs). We evaluated the prevalence of serum specific IgE and IgG antibodies to cephalosporin-human serum albumin (HSA) conjugate and to identify potential genetic risk factors associated with sensitization to cephalosporins in exposed HCWs. The study population consisted of 153 HCWs who had been exposed to antibiotics in a single university hospital and 86 unexposed healthy controls. A questionnaire survey of work-related symptoms (WRS) was administered. A skin-prick test (SPT) was performed, and serum-specific IgE and IgG antibodies to 3 commonly prescribed cephalosporins were measured by ELISA. Four single-nucleotide polymorphisms of the candidate genes related to IgE sensitization were genotyped. The prevalence of WRS to cephalosporins was 2.6%. The prevalence rates of serum-specific IgE and IgG antibodies to cephalosporins were 20.3% and 14.7%, respectively. The FcεR1β-109T > C polymorphism was significantly associated with IgE sensitization to cephalosporins in HCWs (P = 0.036, OR = 3.553; CI, 1.324-9.532). The in vitro functional assay demonstrated that the T allele of FcεR1β-109T had greater promoter activity than did the C allele (P < 0.001). The FcεR1β-109T > C polymorphism may be a potential genetic risk factor for increased IgE sensitization to cephalosporins.

Fine-Tuning of Mast Cell Activation by FcεRIβ Chain

Mast cells play a key role in allergic reaction and disorders through the high affinity receptor for IgE (Fc_εRI) which is primarily activated by IgE and antigen complex. In humans, mast cells express two types of Fc_εRI on the cell surface, tetrameric αβγ₂ and trimeric αγ₂, whereas in mice, the tetrameric αβγ₂ type is exclusively expressed. In human allergic inflammation lesions, mast cells increase in number and preferentially express the αβγ₂ type Fc_εRI. By contrast, in the lesion of non-allergic inflammation, mast cells mainly express the αγ₂type. Since the β chain amplifies the expression and signaling of FcεRI, mast cell effector functions and allergic reaction in vivo are enhanced in the presence of the β chain. In contrast, a truncated β chain-isoform (βT) inhibits FcεRI surface expression. The human Fc_εRIβ gene contains seven exons and a repressor element located in the forth intron, through which Fc_εRIβ transcription is repressed in the presence of GM-CSF. Regarding the additional signal regulatory function of the β chain, the β chain ITAM has dual (positive and negative) functions in the regulation of the mast cell activation. Namely, the Fc_εRIβ chain ITAM enhances the mast cell activation signal triggered by a low-intensity (weak) stimulation whereas it suppresses the signal triggered by high-intensity (strong) stimulation. In an oxazolone-induced mouse CHS model, IgE-mediated mast cell activation is required and the β chain ITAM is crucially involved. Adenosine receptor, one of the GPCRs, triggers a synergistic degranulation response with FcεRI in mast cells, for which the β chain ITAM critically plays positive role, possibly reflecting the in vivo allergic response. These regulatory functions of the FcεRIβ ITAM finely tune FcεRI-induced mast cell activation depending on the stimulation strength, enabling the Fc_εRIβ chain to become a potential molecular target for the development of new strategies for therapeutic interventions for allergies.

Immunoglobulin E-binding reactivities of natural pollen grain extracts from selected grass species in the Philippines

Background

Pollen grains have been reported to be present in the Philippine atmosphere but studies regarding their allergenicity are limited.

Objective

The present study aimed to profile the sensitization of allergic individuals to selected grass pollen species and to characterize the pollen proteins that may be responsible for this allergenic response.

Methods

The protein profile of the grass pollen extracts from Cynodon dactylon, Saccharum spontaneum, Sporobulus indicus, Chloris barbata, Oryza sativa, Imperata cylindrica, and Zea mays was analyzed by Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis. The specific-IgE profile of the allergic individuals and the allergenic potential of the pollen extracts were evaluated through Enzyme-linked Immunosorbent Assay and IgE immunoblotting.

Results

Sensitization of the allergic individuals to the pollen extracts was detected with I. cylindrica and O. sativa to be the most frequently recognized with more that 92% reactivity, whereas for C. dactylon and Z. mays, were found to have less than 25% reactivity.

Conclusion

Multiple IgE-binding proteins from S. indicus, S. spontaneum and C. barbata that were detected may be responsible for the allergic reactions among Filipino subjects.

Pharmacogenetics of asthma in children

Allergic diseases such as bronchial asthma and atopic dermatitis develop by a combination of genetic and environmental factors. Several candidate causative genes of asthma and atopy have been reported as the genetic factors. The clinical features of patients and causes of diseases vary. Therefore, personalized medicine (tailor-made medicine) is necessary for the improvement of quality of life (QOL) and for asthma cure. Pharmacogenetics is very important for personalized medicine. Here, we present the genetics and pharmacogenetics of asthma in children. Finally, we show the guideline for personalized medicine for asthma, particularly in childhood, including the pharmacogenetics of anti-asthmatic drugs, preliminarily produced by the authors.

Genetics of food allergy

PURPOSE OF REVIEW

Food allergy, a growing clinical and public health problem in the United States and worldwide, is likely determined by multiple environmental and genetic factors. The purpose of this review is to summarize recent advances in food allergy genetic research.

RECENT FINDINGS

There is compelling evidence that genetic factors may play a role in food allergy. However, the specific genetic loci that may modulate individual risk of food allergy remain to be identified. To date, only a limited number of candidate gene association studies of food allergy have been reported. Polymorphism(s) in nine genes have been associated with the incidence of food allergy or food allergy severity in at least one study. But most of these findings remain to be replicated in independent populations. In contrast, there are considerable advances in genetics of other allergic diseases such as asthma and atopic dermatitis. Although asthma and atopic dermatitis often coexist with food allergy, the relevance of their candidate genes to food allergy remains to be evaluated.

SUMMARY

Genetics in food allergy is a promising research area but is still in its infancy. More studies are needed to dissect susceptible genes of food allergy. A genome-wide association approach may serve as a powerful tool to identify novel genes related to food allergy. Furthermore, the role of gene-environment interaction, gene-gene interaction, and epigenetics in food allergy remains largely unexplored. Given the complex nature of food allergy, future studies need to integrate environment, genomics, and epigenomics in order to better understand the multifaceted etiology and biological mechanisms of food allergy.

Involvement of Fc(epsilon)R1beta gene polymorphisms in susceptibility to atopy in Korean children with asthma

INTRODUCTION

IgE-dependent activation of mast cells and basophils through the high-affinity IgE receptor (Fc(epsilon)R1) is involved in the pathogenesis of allergen-induced immune responsiveness in atopic disease including bronchial asthma.

MATERIALS AND METHODS

We genotyped 650 children for allelic determinants at two polymorphic sites, -109T/C and E237G, in the Fc(epsilon)R1beta gene by SNP-IT assays using the SNP stream 25K system.

RESULTS

Distributions of the genotype and allele frequencies of Fc(epsilon)R1beta -109T/C and E237G polymorphisms were significantly associated with atopy (P < 0.05) and elevated serum IgE levels. However, differences in the E237G polymorphism did not reach statistical significance after adjustment for multiple comparisons. The genotypes TC or CC at -109T/C were associated with decreased forced expiratory flow(25-75%) in children with asthma (P < 0.05), but this did not reach statistical significance after correction for multiple comparisons. In addition, haplotype 1 (T-A) was associated with atopy susceptibility (P = 0.0069). Analysis of genotype distributions of haplotypes demonstrated a significantly lower PC(20) for homozygous -/- diploids compared with homozygous Ht1/Ht1 (P = 0.0261).

CONCLUSION

Polymorphisms in the Fc(epsilon)R1beta gene confer susceptibility to atopy in Korean children and may have a disease-modifying effect on airways of asthmatic patients.

The first transmembrane region of the beta-chain stabilizes the tetrameric Fc epsilon RI complex

The family of activating immune receptors stabilizes via the 3-helix assembly principle. A charged basic transmembrane residue interacts with two charged acidic transmembrane residues and forms a 3-helix interface to stabilize receptor complexes in the lipid bilayer. One family member, the high affinity receptor for IgE, Fc epsilon RI, is a key regulator of immediate allergic responses. Tetrameric Fc epsilon RI consists of the IgE-binding alpha-chain, the multimembrane-spanning beta-chain and a dimer of the gamma-subunit (Fc epsilon R gamma). Comparative analysis of these seven transmembrane regions indicates that Fc epsilon RI does not meet the charge requirements for the 3-helix assembly mechanism. We performed alanine mutagenesis to show that the only basic amino acid in the transmembrane regions, beta K97, is not involved in Fc epsilon RI stabilization or surface upregulation, a hallmark function of the beta-chain. Even a beta K97E mutant is functional despite four negatively charged acidic amino acids in the transmembrane regions. Using truncation mutants, we demonstrate that the first uncharged transmembrane domain of the beta-chain contains the interface for receptor stabilization. In vitro translation experiments depict the first transmembrane region as the internal signal peptide of the beta-chain. We also show that this beta-chain domain can function as a cleavable signal peptide when used as a leader peptide for a Type I protein. Our results provide evidence that tetrameric Fc epsilon RI does not assemble according to the 3-helix assembly principle. We conclude that receptors formed with multispanning proteins use different mechanisms of shielding transmembrane charged amino acids.

Endogenous suppression of mast cell development and survival by IL-4 and IL-10

Mast cell development is an important component of atopic and chronic inflammatory diseases such as asthma, multiple sclerosis, rheumatoid arthritis, and atherosclerosis. In this study, we found that IL-4 and IL-10 were produced constitutively in cultures of developing mast cells, correlating with mast cell purity. Deletion of either gene increased mast cell numbers and Fc epsilon RI expression during culture in IL-3 + stem cell factor (SCF). By adding exogenous IL-4 and IL-10 to bone marrow (BM) cultures containing IL-3 + SCF, we found that IL-4 + IL-10 suppressed mast cell development through mechanisms not used by either cytokine alone. IL-4 + IL-10 elicited a rapid cell death coincidental with reduced Kit receptor expression and signaling and enhanced mitochondrial damage and caspase activation. IL-4 or IL-10 costimulation, unlike either cytokine alone, altered mast cell ontogeny to yield predominantly macrophages in cultures that typically produce mast cells. This effect was observed consistently with unseparated BM cells, purified mouse BM stem cells, and erythrocyte-depleted human umbilical cord blood cells. These experiments demonstrated a major role for Stat6 and Stat3, but not the Stat3-induced transcriptional repressor Ets variant gene 3. Genetic background was also a critical factor, as BALB/c-derived BM cells were completely resistant to IL-10-mediated killing and expressed lower levels of IL-10R. Collectively, these results support the theory that IL-4 and IL-10 function as endogenous regulators of mast cell progenitor development, consistent with a role in immune homeostasis. Loss of this homeostasis, perhaps via genetic polymorphism, could contribute to the etiology of mast cell-associated disease.

Genome-wide scan on total serum IgE levels identifies FCER1A as novel susceptibility locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85 x 10(-20) and 7.08 x 10(-19) in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78 x 10(-4) and P = 1.95 x 10(-3)). The "top" SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28 x 10(-7)-4.46 x 10(-8)) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels.

High-affinity IgE receptor-beta chain expression in human mast cells

The high-affinity IgE receptor (FcεRI)-β gene is one of the atopy-associated genes, but its biological significance is largely unknown. In this study, we generated the anti-FcεRI-β chain antibody to clarify β-chain protein expression in human mast cells. The FcεRI-β antibody showed specific binding to a 27 kDa protein with Western blotting and membrane bound immunostaining using cultured mast cells. Monomeric IgE sensitization increased β-chain expression as well as mature α-chain expression in mast cells. Upregulation of β-chain expression with monomeric IgE treatment suggests possible roles of FcεRI-β protein as an atopy-related molecule.

Asthma from a pharmacogenomic point of view

Pharmacogenomics, a fascinating, emerging area of biomedical research is strongly influenced by growing availability of genomic databases, high-throughput genomic technologies, bioinformatic tools and artificial computational modelling approaches. One main area of pharmacogenomics is the discovery of new drugs and drug targets with molecular genetic, genomic or even bioinformatic methods; the other is the study of how genomic differences influence the variability in patients' responses to drugs. From a genetic point of view, asthma is multifactorial, which means that the susceptibility to the disease is determined by interactions between multiple genes, and involves important non-genetic factors such as the environment for their expression. In this review, we summarize collective evidence from linkage and association studies that have consistently reported suggestive linkage or association of asthma or its associated phenotypes to polymorphic markers and single nucleotide polymorphisms in selected chromosomes. Genes that have been found implicated in the disease are potential new drug targets and several pharmacological investigations are underway to utilize these new discoveries. Next, we will focus on the inter-individual variability in anti-asthmatic drug responses and review the recent results in this topic.

Discovering susceptibility genes for asthma and allergy

Asthma and asthma-related traits are complex diseases with strong genetic and environmental components. Rapid progress in asthma genetics has led to the identification of several candidate genes that are associated with asthma-related traits. Typically the phenotypic impact of each of these genes, including the ones most often replicated in association studies, is mild, but larger effects may occur when multiple variants synergize within a permissive environmental context. Despite the achievements made in asthma genetics formidable challenges remain. The development of novel, powerful tools for gene discovery, and a closer integration of genetics and biology, should help to overcome these challenges.

The genetic and environmental basis of atopic diseases

The prevalence of atopic diseases has increased abruptly in recent years in most Westernized societies, making the question why this happened the topic of a heated debate. The best paradigm available to date to explain this steep rise, the 'hygiene hypothesis', supports that it is the excess 'cleanliness' of our environments that has led to the decline in the number of infectious stimuli that are necessary for the proper development of our immune system. Recent findings support that it is the combined effect that not only pathogenic, but also non-pathogenic microorganisms, and even their structural components,can exert on the immune system that deters from the development of atopic responses. Adding to these results are intriguing new findings on the effect different gene polymorphisms can have on an individual's predisposition to allergic diseases. The most important linkages produced, to date, include those among the genes for IL-4, IL-13, HLA-DRB, TNF, LTA,FCER1B, IL-4RA, ADAM33, TCR alpha/delta, PHF11, GPRA, TIM, p40, CD14, DPP10, T-bet, GATA-3, and FOXP3 and allergic disorders. The two parallel research efforts, epidemiologic and genetic, are only recently starting to converge,producing fascinating results on the effect particular gene-environment interactions might have in the development of atopy.The most important lesson learned through this tremendous research effort is that not only a small number but thousands and millions of separate risk factors act in concordance in the production of the allergic phenotype.

Genetic variability of the high-affinity IgE receptor alpha subunit (Fc epsilon RI alpha) is related to total serum IgE levels in allergic subjects

Known susceptibility genes to atopy and asthma have been identified by linkage or associations with clinical phenotypes, including total serum IgE levels. IgE-mediated sensitivity reactions require a high-affinity IgE receptor (FcepsilonRI), which immobilizes the immunoglobulin on the surface of the effector cells, mostly mast cells and basophils. In this mini-review, recent findings are presented on genetic variation of this receptor, as related to atopy. Transcription of FCER1A gene encoding the receptor alpha subunit can be initiated from two separate promoters, the proximal one and the distal one, which results in a transcript containing two novel untranslated exons (1A, 2A). Our knowledge on the role of this mechanism in allergic diseases is still at an infancy stage. Within regulatory elements of FCER1A some common single nucleotide polymorphisms have functional associations, which were recently reported and replicated in different ethnical groups. Interestingly, these associations do not confer susceptibility to allergic diseases, but rather modulate serum concentrations of IgE. Similarly to the previously investigated beta subunit of the receptor, FCER1A is a good candidate for a quantitative trait locus (QTL) in allergic diseases, and appears to participate in the systemic regulation of IgE levels.

Association and functional relevance of E237G, a polymorphism of the high-affinity immunoglobulin E-receptor beta chain gene, to airway hyper-responsiveness

BACKGROUND

The hyper-sensitivity reaction of IgE, with its high-affinity receptors (FcepsilonRI), is central to the phenomenon of atopic diseases.

OBJECTIVE

To evaluate the genetic effects of non-synonymous single-nucleotide polymorphisms (SNPs) of FcepsilonRI on intermediate phenotypes of asthma, i.e. atopy and airway hyper-responsiveness (AHR), in the Korean general population.

SUBJECTS AND METHODS

Atopy and AHR were evaluated in a cohort of 2055 subjects, aged 10-18 years, using skin prick tests (SPTs) for common aeroallergens and total serum IgE and methacholine bronchial provocation tests. All FcepsilonRI-alpha, FcepsilonRI-beta, and FcepsilonRI-gamma gene exons of 24 healthy subjects were sequenced to locate informative non-synonymous SNPs (minor allele frequency>2%). Informative SNPs were then scored, using the high-throughput single base extension method. Relative risk (RR) was determined by multiple logistic regression analysis, after adjusting for confounding factors. The functional relevance of non-synonymous SNPs was analysed using the sorting intolerant from tolerant (SIFT) program.

RESULTS

The SNP search found only one informative non-synonymous SNP in FcepsilonRI-beta: E237G (minor allele frequency=0.21). The positive rate of AHR was lower among subjects with the 237*E allele than among those with 237*G [RR (95% confidence interval)=0.41 (0.19-0.89); P=0.01]. However, the E237G substitution was not associated with either a positive SPT response or total serum IgE levels. Sequence evolution analysis predicted that the E237G variation is an intolerant amino acid substitution, with functional importance.

CONCLUSION

In the Korean general population, AHR is significantly associated with the E237G polymorphism of FcepsilonRI-beta, which results in an intolerant amino acid substitution.

[Review of sick house syndrome]

'Sick house syndrome' (SHS) is a health issue that closely resembles sick building syndrome (SBS) that had occurred in European countries. The aim of this review is to clarify the characteristics of SHS by reviewing previous reports rigorously. We propose the definition of SHS as "health impairments caused by indoor air pollution, regardless of the place, causative substance, or pathogenesis". Cases of SBS are reported to occur predominantly in offices and sometimes schools, whereas those of SHS are usually found in general dwellings. In many cases, SHS is caused by biologically and/or chemically polluted indoor air. Physical factors might affect the impairments of SHS in some cases. It is considered that symptoms of SHS develop through toxic, allergic and/or some unknown mechanisms. Psychological mechanisms might also affect the development of SHS. It is still unclear whether SBS and SHS are very close or identical clinical entities, mostly because a general agreement on a diagnostic standard for SHS has not been established. Previous research gradually clarified the etiology of SHS. Further advances in research, diagnosis, and treatment of SHS are warranted with the following measures. Firstly, a clinical diagnostic standard including both subjective and objective findings must be established. Secondly, a standard procedure for assessing indoor air contamination should be established. Lastly, as previous research indicated multiple causative factors for SHS, an interdisciplinary approach is needed to obtain the grand picture of the syndrome.

Genetic polymorphisms at FCER1B and PAI-1 and asthma susceptibility

BACKGROUND

We previously detected a promoter polymorphism (- 109C/T) in the gene for the beta-chain of the high-affinity receptor for IgE (FCER1B), which was associated with total serum IgE levels but not with asthma in a Japanese population. A genetic interaction is biologically plausible between FcepsilonRI-beta and the plasminogen activator inhibitor 1 (PAI-1), which is highly expressed in mast cells in asthmatics and plays an essential role in airway remodelling. We hypothesized that FCER1B promoter polymorphisms, by modifying the intensity of mast cell activation signals, modulate the genetic effects of a functional 4G/5G polymorphism in the PAI-1 gene on asthma. OBJECTICIVE: To examine whether FCER1B promoter polymorphisms (- 109C/T and - 654C/T) influence the genetic effects of the functional polymorphism (4G/5G) at the PAI-1 promoter region on asthma susceptibility using a case-control analysis.

METHODS

Subjects (374 asthmatic patients and 374 non-asthmatic controls) were divided into combined genotype groups based on the presence of FCER1B - 109TT and - 654CC genotypes and the PAI-1 4G allele. Logistic regression analysis was used to estimate adjusted odds ratios for asthma associated with the different genotype groups.

RESULTS

Individuals homozygous for the FCER1B - 109T/ - 654C haplotype and the PAI - 1 5G allele had a reduced susceptibility to asthma; the odds ratio for the development of asthma was 0.20 (95% confidence interval, 0.084 - 0.46; P = 0.00015) for them, compared with individuals also homozygous for the - 109T/- 654C haplotype at FCER1B but carrying the 4G allele at PAI-1. The regression model also showed an interaction of the PAI-1 4G/5G genotype with the FCER1B-109C/T (P for interaction = 0.0017) or FCER1B-654C/T (P for interaction = 0.031) on asthma.

CONCLUSION

The present findings suggest a synergistic interaction between FCER1B and PAI-1 genes in asthma susceptibility.

Influence of SNPs in cytokine-related genes on the severity of food allergy and atopic eczema in children

Although many single nucleotide polymorphism (SNP) studies have reported an association of atopy, allergic diseases and total serum immunoglobulin E (IgE) levels, almost all of these studies sought risk factors for the onset of these allergic diseases. Furthermore, many studies have analyzed a single gene and hardly any have analyzed environmental factors. In these analyses, the results could be masked and the effects of other genes and environmental factors may be decreased. Here, we described the correlation between four genes [interleukin (IL)-4 (C-590T), IL-4 receptor (A1652G), FCER1B (G6842A) and STAT6 (G2964A)] in connection with IgE production; the role of IL-10 (C-627A) as a regulatory cytokine of allergy; and the severity of food allergy (FA) and atopic eczema (AE) in 220 Japanese allergic children. In addition to these SNPs, environmental factors, i.e., patient's attitude, indoor environment, and so on, were also investigated in this study. Our study was retrospective, and the correlation was analyzed by our defined clinical scores divided into three terms: worst symptoms, recent symptoms and general amelioration at the most recent examination during the disease course. Our results indicated that IL-10 AA, the genotype with lower IL-10 production, is associated with higher IgE levels in the serum (p < 0.0001, estimate; 0.912). Marginal liver abnormalities were observed in the subject group with both FA and AE (p < 0.1191, estimate; 0.1490). Our defined clinical scores enabled evaluation of various aspects of disease severity. Based on the scores, while no single SNP selected in this study determined severity, the combination of the SNP with laboratory data and environmental factors appeared to determine severity.

Fcε- and Fcγ-receptor signaling in diseases

It has become increasingly clear that receptors for the immunoglobulin Fc region play pivotal roles in immune homeostasis and disease. This review describes the fine regulation of the high-affinity IgE-receptor (FcepsilonRI) signaling, especially focusing on the early events that are coordinately regulated by Src family protein tyrosine kinases (PTKs), FcepsilonRI beta-subunit, and membrane lipid rafts. Because allergen-mediated FcepsilonRI cross-linking leads to the synthesis and release of a variety of proinflammatory mediators and cytokines, the duration and amplitude of the signal need to be strictly controlled, and the counterbalancing signaling is provided by specialized inhibitory receptors and molecules. However, recent work have revealed that Src family PTKs and FcepsilonRI beta-subunit transduce both positive and negative signaling with unexpectedly complex mechanisms. FcgammaRIIB exerts a unique inhibitory function on cell activation processes after the engagement of Fcgamma, FcepsilonRI and B cell receptors. Recent work has shown that FcgammaRIIB polymorphisms are associated with systemic lupus erythematosus, and that a transmembrane polymorphism in FcgammaRIIB results in an impaired distribution to lipid rafts and a reduced inhibitory function. Studies addressing the functions of disease-associated polymorphisms in the FcepsilonRI beta-subunit and low-affinity FcgammaRs are also considered.

IgE and FcepsilonRI regulation

The high-affinity immunoglobulin (Ig)E receptor, FcepsilonRI, regulates the action of mast cells and basophils and therefore, regulates the expression of atopic disease. There have been several recent observations that demonstrate new behaviors for this receptor. The control of FcepsilonRI expression, control of cell function by FcepsilonRI, and expression of FcepsilonRI on other cell types are important new areas of understanding currently being explored.

[Therapeutic effect of Xincang Decoction on chronic airway inflammation in children with bronchial asthma in remission stage]

OBJECTIVE

To observe the therapeutic effect of Xincang Decoction on chronic airway inflammation in children with asthma in clinical investigation.

METHODS

Xincang Decoction was composed of Flos Magnoliae (Xinyi) and Fructus Xanthii (Cangoerzi), the traditional Chinese herbs for expelling wind. Sixty cases of children with bronchial asthma in remission stage were randomly divided into two groups. Thirty cases in the treatment group were treated with Xincang Decoction and the others in the control group were treated with ketotifen fumarate. The therapeutic effects of the two groups were compared, and the peripheral eosinophil (EOS) count, the levels of immunoglobulin E (IgE), interleukin 4 (IL-4) and interleukin 5 (IL-5), and the pulmonary functions were observed before and three months after the treatment.

RESULTS

After three months treatment, the results showed that the total response rates of the treatment and the control group were 83.3% and 80.0%, respectively, without marked difference (P>0.05). The levels of EOS and IL-5 were obviously decreased after the treatment, and the levels of EOS and IL-5 of the patients in the treatment group were lower than those in the control group (P<0.05). Meanwhile the forced expiratory volume in one second (FEV(1)) was improved after the treatment, and the FEV(1) of the patients in the treatment group was higher than that of the patients in the control group (P<0.05).

CONCLUSION

Xincang Decoction can decrease the levels of EOS and IL-5 and improve the pulmonary function in treating chronic airway inflammation in children with bronchial asthma in remission stage.

Analysis of polymorphisms in 16 genes in type 1 diabetes that have been associated with other immune-mediated diseases

BACKGROUND

The identification of the HLA class II, insulin (INS), CTLA-4 and PTPN22 genes as determinants of type 1 diabetes (T1D) susceptibility indicates that fine tuning of the immune system is centrally involved in disease development. Some genes have been shown to affect several immune-mediated diseases. Therefore, we tested the hypothesis that alleles of susceptibility genes previously associated with other immune-mediated diseases might perturb immune homeostasis, and hence also associate with predisposition to T1D.

METHODS

We resequenced and genotyped tag single nucleotide polymorphisms (SNPs) from two genes, CRP and FCER1B, and genotyped 27 disease-associated polymorphisms from thirteen gene regions, namely FCRL3, CFH, SLC9A3R1, PADI4, RUNX1, SPINK5, IL1RN, IL1RA, CARD15, IBD5-locus (including SLC22A4), LAG3, ADAM33 and NFKB1. These genes have been associated previously with susceptibility to a range of immune-mediated diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Graves' disease (GD), psoriasis, psoriatic arthritis (PA), atopy, asthma, Crohn disease and multiple sclerosis (MS). Our T1D collections are divided into three sample subsets, consisting of set 1 families (up to 754 families), set 2 families (up to 743 families), and a case-control collection (ranging from 1,500 to 4,400 cases and 1,500 to 4,600 controls). Each SNP was genotyped in one or more of these subsets. Our study typically had approximately 80% statistical power for a minor allele frequency (MAF) >5% and odds ratios (OR) of 1.5 with the type 1 error rate, alpha = 0.05.

RESULTS

We found no evidence of association with T1D at most of the loci studied 0.02

CONCLUSION

Polymorphisms in a variety of genes previously associated with immune-mediated disease susceptibility and/or having effects on gene function and the immune system, are unlikely to be affecting T1D susceptibility in a major way, even though some of the genes tested encode proteins of immune pathways that are believed to be central to the development of T1D. We cannot, however, rule out effect sizes smaller than OR 1.5.

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Key Words Collapse

MESH Headings

• ADAM Proteins/genetics
• Case-Control Studies
• Diabetes Mellitus, Type 1/genetics
• Genetic Predisposition to Disease
• Humans
• Immune System Diseases/genetics
• Polymorphism, Single Nucleotide

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Grants

• Wellcome Trust
• G0000934 Medical Research Council
• 068545/Z/02 Wellcome Trust

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Affiliation(s)

Deborah J Smyth Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Joanna MM Howson Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Felicity Payne Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Lisa M Maier Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Rebecca Bailey Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Kieran Holland Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Christopher E Lowe Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Jason D Cooper Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
John S Hulme Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Adrian Vella Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Ingrid Dahlman Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Alex C Lam Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Sarah Nutland Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Neil M Walker Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Rebecca CJ Twells Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
John A Todd Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK

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Candidate gene association studies and evidence for gene-by-gene interactions

Candidate gene studies in asthma are a powerful and valuable tool in asthma genetics. Although the quality of small-scale, freely associating studies has been questionable, increasingly serious efforts are made to establish, replicate, and verify association results. Association studies may help us to better understand the mechanisms underlying asthma. They may create hypotheses and help to direct functional studies to targets that are likely to give valuable results. However, they should not be over-interpreted; only biologic proof can verify associations between genetic variations and a certain disease outcome. The insight that gene-by-gene and gene-by-environment interactions may be crucial for understanding and pinpoint the complex mechanisms of genetic regulation of multifactorial diseases has gained momentum in the last years when technical improvement allowed for the effective genotyping and analysis of great numbers of polymorphisms in large populations. It can be expected that from this area of research new and exciting results will follow soon.