Immunological and genetic aspects of asthma and allergy (original) (raw)
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Genetics of asthma: a molecular biologist perspective
Clinical and Molecular Allergy, 2009
Asthma belongs to the category of classical allergic diseases which generally arise due to IgE mediated hypersensitivity to environmental triggers. Since its prevalence is very high in developed or urbanized societies it is also referred to as "disease of civilizations". Due to its increased prevalence among related individuals, it was understood quite long back that it is a genetic disorder. Well designed epidemiological studies reinforced these views. The advent of modern biological technology saw further refinements in our understanding of genetics of asthma and led to the realization that asthma is not a disorder with simple Mendelian mode of inheritance but a multifactorial disorder of the airways brought about by complex interaction between genetic and environmental factors. Current asthma research has witnessed evidences that are compelling researchers to redefine asthma altogether. Although no consensus exists among workers regarding its definition, it seems obvious that several pathologies, all affecting the airways, have been clubbed into one common category called asthma. Needless to say, genetic studies have led from the front in bringing about these transformations. Genomics, molecular biology, immunology and other interrelated disciplines have unearthed data that has changed the way we think about asthma now. In this review, we center our discussions on genetic basis of asthma; the molecular mechanisms involved in its pathogenesis. Taking cue from the existing data we would briefly ponder over the future directions that should improve our understanding of asthma pathogenesis.
Investigating highly replicated asthma genes as candidate genes for allergic rhinitis
BMC Medical Genetics, 2013
Background: Asthma genetics has been extensively studied and many genes have been associated with the development or severity of this disease. In contrast, the genetic basis of allergic rhinitis (AR) has not been evaluated as extensively. It is well known that asthma is closely related with AR since a large proportion of individuals with asthma also present symptoms of AR, and patients with AR have a 5-6 fold increased risk of developing asthma. Thus, the relevance of asthma candidate genes as predisposing factors for AR is worth investigating. The present study was designed to investigate if SNPs in highly replicated asthma genes are associated with the occurrence of AR. Methods: A total of 192 SNPs from 21 asthma candidate genes reported to be associated with asthma in 6 or more unrelated studies were genotyped in a Swedish population with 246 AR patients and 431 controls. Genotypes for 429 SNPs from the same set of genes were also extracted from a Singapore Chinese genome-wide dataset which consisted of 456 AR cases and 486 controls. All SNPs were subsequently analyzed for association with AR and their influence on allergic sensitization to common allergens. Results: A limited number of potential associations were observed and the overall pattern of P-values corresponds well to the expectations in the absence of an effect. However, in the tests of allele effects in the Chinese population the number of significant P-values exceeds the expectations. The strongest signals were found for SNPs in NPSR1 and CTLA4. In these genes, a total of nine SNPs showed P-values <0.001 with corresponding Q-values <0.05. In the NPSR1 gene some P-values were lower than the Bonferroni correction level. Reanalysis after elimination of all patients with asthmatic symptoms excluded asthma as a confounding factor in our results. Weaker indications were found for IL13 and GSTP1 with respect to sensitization to birch pollen in the Swedish population.
Immunology and Allergy Clinics of North America, 2015
The allergic diseases are complex phenotypes for which a strong genetic basis has been firmly established. Genome-wide association studies (GWAS) has been widely employed in the field of allergic disease, and to date significant associations have been published for nearly 100 asthma genes/loci, in addition to multiple genes/loci for AD, AR and IgE levels, for which the overwhelming number of candidates are novel and have given a new appreciation for the role of innate as well as adaptive immune-response genes in allergic disease. A major outcome of GWAS in allergic disease has been the formation of national and international collaborations leading to consortia meta-analyses, and an appreciation for the specificity of genetic associations to subphenotypes of allergic disease. Molecular genetics has undergone a technological revolution, leading to next generation sequencing (NGS) strategies that are increasingly employed to hone in on the causal variants associated with allergic diseases. Unmet needs in the field include the inclusion of ethnically and racially diverse cohorts, and strategies for managing 'big data' that is an outcome of technological advances such as sequencing.
Toxicology Letters, 1996
Asthma and airways hy~r~s~nsiveness are the respiratory manifestations of sensitization to exogenous materials including protein allergens and chemical sensitizers that may trigger ongoing inflammation and respiratory symg tomatology in those people who are predisposed to develop the asthmatic syndrome. That genetics plays a major role in this particular syndrome is without question, since twin studies have shown a greater prevalence of disease for monozygotic as opposed to dizygotic twins. There have been the ~ginnin~ of the development of an approach to a number of candidate genes for major genetic input in the asthmatic syndrome. However, unlike cystic fibrosis or even other autoimmune and inflammatory diseases such as juvenile diabetes and/or multiple sclerosis, a single gene or a significant set of major genes may not be easily identified. Rather the small contribution of multiple genes and/or sets of genes may be summed together and added to environmen~i exposure in people who will develop asthmatic syndromes. The identification of a genetic component to asthma would be of great significance. Even without a major or predominant gene, identification of the minor sets of genes interacting to cause asthma would represent a great advance. Knowledge of those minor genetic alleles involved in asthma susceptibility would allow great latitude in offering diagnostic screening and new therapeutic inte~entions in asthma.
Clinical & Experimental Allergy, 2009
Background Common polymorphisms have been identified in genes suspected to play a role in asthma. We investigated their associations with wheeze and allergy in a case-control sample from Phase 2 of the International Study of Asthma and Allergies in Childhood. Methods We compared 1105 wheezing and 3137 non-wheezing children aged 8-12 years from 17 study centres in 13 countries. Genotyping of 55 candidate single nucleotide polymorphisms (SNPs) in 14 genes was performed using the Sequenom System. Logistic regression models were fitted separately for each centre and each SNP. A combined per allele odds ratio and measures of heterogeneity between centres were derived by random effects meta-analysis. Results Significant associations with wheeze in the past year were detected in only four genes (IL4R, TLR4, MS4A2, TLR9, Po0.05), with per allele odds ratios generally o1.3. Variants in IL4R and TLR4 were also related to allergen-specific IgE, while polymorphisms in FCER1B (MS4A2) and TLR9 were not. There were also highly significant associations (Po0.001) between SPINK5 variants and visible eczema (but not IgE levels) and between IL13 variants and total IgE. Heterogeneity of effects across centres was rare, despite differences in allele frequencies. Conclusions Despite the biological plausibility of IgE-related mechanisms in asthma, very few of the tested candidates showed evidence of association with both wheeze and increased IgE levels. We were unable to confirm associations of the positional candidates DPP10 and PHF11 with wheeze, although our study had ample power to detect the expected associations of IL13 variants with IgE and SPINK5 variants with eczema.
Interactions between genes and environmental factors in asthma and atopy: new developments
Respiratory research
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.