Howard TD, etal., Am J Hum Genet. 2002 Jan;70(1):230-6. Epub 2001 Nov 14.
Asthma is a common respiratory disease that is characterized by variable airways obstruction caused by acute and chronic bronchial inflammation; associated phenotypes include bronchial hyperresponsiveness (BHR), elevated total serum immunoglobulin E (IgE) levels, and skin tests positive to common al
lergens. Binding of interleukin-13 (IL13) or interleukin-4 (IL4) to the IL4 receptor (IL4R) induces the initial response for Th2 lymphocyte polarization. Both IL13 and IL4 are produced by Th2 cells and are capable of inducing isotype class-switching of B-cells to produce IgE after allergen exposure. These cytokines also share a common receptor component, IL4R alpha. We have investigated five IL4RA single-nucleotide polymorphisms in a population of Dutch families ascertained through a proband with asthma. By considering the probands and their spouses as an unrelated sample, we observed significant associations of atopy and asthma-related phenotypes with several IL4RA polymorphisms, including S478P and total serum IgE levels (P=.0007). A significant gene-gene interaction between S478P in IL4RA and the -1111 promoter variation in IL13, previously shown to be associated with BHR (P=.003), was detected. Individuals with the risk genotype for both genes were at almost five times greater risk for the development of asthma compared to individuals with both non-risk genotypes (P=.0004). These data suggest that variations in IL4RA contribute to elevated total serum IgE levels, and interaction between IL4RA and IL13 markedly increases an individual's susceptibility to asthma.
Llanes E, etal., Int Arch Allergy Immunol. 2009;148(3):228-38. doi: 10.1159/000161583. Epub 2008 Oct 10.
BACKGROUND: Previous results demonstrated that sensitization to specific olive pollen allergens could be related with a different clinical pattern (asthma and/or rhinitis), and that specific patterns of sensitization are regulated by different HLA class II antigens. The authors analyze the possible
implication of 7 genetic polymorphisms described as asthma susceptibility genes: IL13 (C-1112T and R130Q), IL4RA (I50V, Q551R), IL5 (C-746T) and ADRB2 (Q27E and R16G) in specific olive pollen allergic sensitization. METHODS: The authors genotyped seven polymorphisms of the IL13, IL4RA, IL5 and ADRB2 genes in 146 patients allergic to olive pollen with seasonal rhinitis/asthma and 50 controls using the polymerase chain reaction-restriction fragment length polymorphism and real-time polymerase chain reaction techniques. RESULTS: Two polymorphisms of IL13 were associated with allergy to olive pollen: the TT genotype of IL13 C-1112T was decreased (odds ratio, OR = 0.35, p = 0.006) whereas the RQ heterozygous genotype of IL13 R130Q increased in patients allergic to olive pollen (OR = 3.12, p = 0.009). The combined analysis of two IL4RA single nucleotide polymorphisms (SNPs) (I50V and Q551R) showed an association with asthma: IL4RA V50/Q551 was associated with risk (OR = 2.48, p = 0.007) whereas the IL4RA V50R551 haplotype was associated with protection (OR = 0.31, p = 0.003). CONCLUSIONS: The IL13 polymorphisms under study were associated with specific allergy to olive pollen: the IL13 C-1112T polymorphism as a protective factor and the IL13 R130Q polymorphism as a risk factor. Interestingly, although single polymorphisms of IL4RA are not associated with any phenotype analyzed, the interaction between IL4RA I50V/Q551R was strongly associated with the asthma phenotype. IL13 and IL4RA could be relevant markers for allergy to olive pollen and asthma development.
Kumar A, etal., J Hum Genet. 2015 Aug;60(8):443-8. doi: 10.1038/jhg.2015.45. Epub 2015 May 21.
Asthma is a complex, multifactorial disease resulting due to dysregulated immune responses. Genetic factors contribute significantly to asthma pathogenesis, and identification of these factors is one of the major goals in understanding the disease. Th1/Th2 helper differentiation has a critical role
in modulating the phenotypes associated with atopic asthma. This study was aimed at identifying genetic modifiers of asthma in selected genes involved in T helper differentiation. A total of 354 single-nucleotide polymorphisms (SNPs) in 33 candidate genes were genotyped in a case-control cohort (cases=147, controls=199) and families (n=247) using Illumina's Golden Gate Assay. Five SNPs, rs3733475A/C (IRF2), rs2069832A/G (IL6), rs2012075G/A (IFNGR2) and rs1400656G/A (STAT4) and rs1805011C/A (IL4RA) were found to be associated with asthma in family based as well as in case-control analyses (P=0.002, P=0.001, P=0.004, P=0.003 and P=0.001, respectively). Interestingly, the minor alleles at these loci showed a protective effect. A five loci haplotype, TAACG, in IRF2 gene, was significantly associated with asthma in families (P=1.1 × 10(-6)) and in case-control cohort (P=0.01). In conclusion, our studies led to identification of some key candidate genes, namely IRF2, IL6, IFNGR2, STAT4 and IL4RA that modulate genetic susceptibility to asthma in the Indian population. Also, this is the first report of independent association of IL6 gene polymorphism with atopic asthma.
Isidoro-Garcia M, etal., Clin Mol Allergy. 2005 Nov 29;3:15.
BACKGROUND: IL4/IL4RA pathway plays an important role in atopy and asthma. Different polymorphisms in IL4 and IL4RA genes have been described. Particularly, -33C>TIL4 and 576Q>RIL4RA SNP
s have been independently associated to atopy and asthma. The purpose of this study was to analyse these polymorphisms in a population of patients with a well-characterized asthma phenotype. METHODS: A total of 212 unrelated Caucasian individuals, 133 patients with asthma and 79 healthy subjects without symptoms or history of asthma or atopy and with negative skin prick tests were recruited. Lung function was measured by spirometry and asthma was specialist physician-diagnosed according to the ATS (American Thoracic Society) criteria and classified following the GINA (Global Initiative for Asthma) guidelines. Skin prick tests were performed according to EAACI recommendations. -33C>TIL4 was studied with TaqMan assay and 576Q>RIL4RA by PCR-RFLP technique. Hardy-Weinberg equilibrium was analysed in all groups. Dichotomous variables were analysed using chi2, Fisher exact test, Monte Carlo simulation test and odds ratio test. To model the effects of multiple covariates logistic regression was used. RESULTS: No statistically significant differences between the group of patients with asthma and the controls were found when the allele and genotype distribution of -33C>TIL4 and 576Q>RIL4RA polymorphisms were compared. However, the T allele of the -33C>TIL4 SNP was more frequent in patients with persistent asthma. Multivariate analysis adjusted for age and sex confirmed that carriers of allele T had an increased risk of persistent asthma (OR: 2.77, 95%CI: 1.18-6.49; p = 0.019). Analysis of combination of polymorphisms showed that patients carrying both the T allele of -33C>TIL4 and the A allele of 576Q>RIL4RA had an increased risk of asthma. This association was particularly observed in persistent asthma [Fisher's p value = 0.0021, Monte Carlo p value (after 10(4) simulations) = 0.0016, OR:3.39; 95% CI:1.50-7.66]. CONCLUSION: Our results show a trend of association between the genetic combination of the T allele of -33C>TIL4 and the A allele of 576Q>RIL4RA with asthma. This genetic variant was more frequently observed in patients with persistent asthma. As long as this study was performed in a small population, further studies in other populations are needed to confirm these results.
Davoodi P, etal., Indian J Med Res. 2015 Dec;142(6):675-80. doi: 10.4103/0971-5916.174551.
BACKGROUND & OBJECTIVES: Interleukin 4 (IL4) and IL13 genes are believed to be responsible for inflammation of the airways in asthmatics. These share a common receptor component called IL4Ralpha which is another potentially important candidate gene linked to asthma phenotypes. Another gene Toll-like
receptor 4 (TLR4) might affect the incidence or progression of asthma through the expression of proinflammatory genes. Several single nucleotide polymorphisms (SNPs) in IL4, IL13, IL4Ralpha and TLR4 have been reported to be linked to asthma or related phenotypes in several ethnic populations using linkage studies and association studies. However, the results have not been consistent. We investigated five SNPs (C-589T and C-33T of IL4, G+2044A of IL13, A+1902G of IL4Ralpha, and A+896G of TLR4) in patients with adult onset asthma to evaluate their role in manifestation and severity of asthma. METHODS: Adult (>18 yr of age) patients with asthma (n=100) and healthy controls (n=50) were included in the study. Genotyping was performed using sequenom MassARRAY technology. RESULTS: The mutant alleles of the C-589T and C-33T SNPs in the promoter region of IL4 were present in 4 per cent patients with asthma but absent from the control group suggesting that the variations in IL4 may contribute to asthma occurrence. The SNPs of other genes were seen in both controls and patients. INTERPRETATION & CONCLUSIONS: The results suggest the possible association between the genetic distribution of C-589T and C-33T SNPs of IL4 with asthma in Indian adults.
