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Association between Interleukin-4 Receptor α Chain (IL4RA) I50V and Q551R Polymorphisms and Asthma Risk: An Update Meta-Analysis

  • Wei Nie ,

    Contributed equally to this work with: Wei Nie, Yuansheng Zang, Jiquan Chen

    Affiliation Department of Respiratory Disease, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China

  • Yuansheng Zang ,

    Contributed equally to this work with: Wei Nie, Yuansheng Zang, Jiquan Chen

    Affiliation Department of Respiratory Disease, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China

  • Jiquan Chen ,

    Contributed equally to this work with: Wei Nie, Yuansheng Zang, Jiquan Chen

    Affiliation Department of Respiratory Disease, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China

  • Qingyu Xiu

    xiu_qingyu@126.com

    Affiliation Department of Respiratory Disease, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China

Association between Interleukin-4 Receptor α Chain (IL4RA) I50V and Q551R Polymorphisms and Asthma Risk: An Update Meta-Analysis

  • Wei Nie, 
  • Yuansheng Zang, 
  • Jiquan Chen, 
  • Qingyu Xiu
PLOS
x

Abstract

Background

The associations between the interleukin-4 receptor α chain (IL4RA) I50V and Q551R polymorphisms and asthma risk remained controversial.

Methods

We searched the Pubmed, Embase, Chinese National Knowledge Infrastructure (CNKI) and Wanfang databases for studies published before February 2013. The strengths of the associations were calculated using odds ratios (ORs) with 95% confidence intervals (CIs).

Results

A total of 50 studies were included in this meta-analysis. There was a significant association between the IL4RA I50V polymorphism and asthma risk in a dominant genetic model (OR = 1.13, 95% CI 1.04–1.23, P = 0.005). The IL4RA Q551R polymorphism was associated with a significantly elevated asthma risk in a recessive genetic model (OR = 1.46, 95% CI 1.22–1.75, P<0.0001). Subgroup analyses found that the IL4RA I50V polymorphism was significantly associated with asthma risk in Asians (OR = 1.72, 95% CI 1.31–2.25, P<0.0001), pediatric asthma risk (OR = 1.50, 95% CI 1.13–1.99, P = 0.005), and atopic asthma risk (OR = 1.88, 95% CI 1.27–2.79, P = 0.002).

Conclusions

The results of this meta-analysis suggested that the IL4RA I50V and Q551R polymorphisms may be risk factors for developing asthma.

Introduction

Asthma is a complex, persistent, inflammatory disease characterized by airway hyper-responsiveness and inflammation. Asthma currently represents a major public health burden in many countries [1]. Thus an understanding of the causes of this disease is an area of intense interest. Cumulative evidence supports an important genetic role in determining asthma risk [2].

T helper-2 (Th2) cytokines, such as interleukin-4 (IL-4) and IL-13, play central roles in allergic inflammation and asthma. They exert their biological activities by binding to their respective cell surface receptors, both of which share the α chain of the IL-4 receptor (IL-4Rα) [3]. Kotsimbos et al. [4] showed that expression levels of IL-4Rα messenger RNA and protein were significantly increased in the epithelium and subepithelium of biopsy specimens from subjects with atopic asthma, compared with atopic control subjects. Additionally, IL-4Rα-deficient mice were unable to produce immunoglobulin E (IgE) and the Th2 inflammatory reaction was markedly diminished [5]. Furthermore, IL-4Rα-targeted antibodies could reduce lung inflammation, airway hyper-­responsiveness and goblet-cell hyperplasia in mouse models of asthma [6]. Therefore, these results indicated that IL-4Rα may play an important role in the pathogenesis of asthma and suggested that IL4RA may be a strong candidate gene for asthma susceptibility.

IL4RA is located on chromosome 16p12.1. Many studies have investigated the associations between the IL4RA polymorphisms and susceptibility to asthma [7][56]. Most of these studies focused on two polymorphisms: I50V (rs1805010) and Q551R (rs1801275). However, the results of these studies have been controversial and inconclusive. A single study may not have sufficient power to detect slight effects of these polymorphisms on asthma because of relatively small sample sizes; however, a meta-analysis may provide more credible evidence by systematically summarizing the existing data. In 2007, Loza and Chang conducted a meta-analysis and concluded that the IL-4RA Q551R polymorphism, but not the I50V polymorphism, was associated with asthma risk [57]. However, that meta-analysis only included 13 studies, and several new studies with more data have been published since 2007. We therefore conducted an up-to-date meta-analysis to re-investigate the association between IL4RA polymorphisms and asthma risk.

Methods

Publication search

A literature search of the PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI), and Wanfang databases was conducted for studies published before February 2013 using combinations of the following terms: (asthma or asthmatic) and (interleukin-4 receptor α chain or IL-4Rα or IL4Rα or IL4RA) and (polymorphism or mutation or variant). All eligible articles were retrieved, and their references were checked for other relevant studies.

Study selection

All selected studies complied with the following three criteria: (1) evaluation of the IL4RA I50V and Q551R polymorphisms and asthma risk; (2) using a case-control design; and (3) genotype distributions in both cases and controls available for estimating an odds ratio (OR) with a 95% confidence interval (CI). If serial studies of the same population from the same group were reported, the largest study was included.

Data extraction

Two investigators (Nie and Chen) independently extracted data from the included studies. The following information was collected from each study: first author's name, year of publication, original country, ethnicity, age group, atopic status, sample size, and genotype number in cases and controls. We verified the accuracy of the data by comparing collection forms between investigators. If different results were generated, the full text of the article was checked.

Qualitative assessment

The quality of included studies was assessed independently by two investigators (Nie and Chen).Table S1 shows the criteria for quality appraisal. The quality scoring system was based on traditional epidemiological considerations and asthma genetic issues [58]. The criteria covered the representativeness of cases and controls, the ascertainment of cases and controls, genotyping examination, Hardy-Weinberg equilibrium (HWE), and association assessment. Scores ranged from the lowest zero to the highest thirteen.

Statistical analysis

A meta-analysis was performed when data from at least three similar studies were available. The strengths of the associations between the IL4RA polymorphisms and asthma risk were measured by ORs and 95% CIs. The statistical significance of summary OR was determined using the Z test. OR1, OR2, and OR3 were calculated for the genotypes: 1). II vs. VV (OR1), IV vs. VV (OR2), and II vs. IV (OR3) for the I50 V polymorphism, 2). RR vs. QQ (OR1), QR vs. QQ (OR2), and RR vs. QR (OR3) for the Q551R polymorphism. These pairwise differences were used to indicate the most appropriate genetic model [59][63]. Once the best genetic model was identified, this model was used to collapse the three genotypes into two groups (except in the case of a co-dominant model) and to pool the results.

HWE was evaluated using the Chi-square test. P<0.05 was considered representative of a departure from HWE. Heterogeneity of effects across studies was assessed using the Chi-square statistic and quantified by I2, which represented the percentage of total variation across studies that was attributable to heterogeneity rather than chance (P<0.10 was considered representative of statistically significant heterogeneity). A fixed-effect model was used when there was no heterogeneity in the studies. Otherwise, the random-effect model was used. Subgroup analyses were performed by stratifying according to ethnicity, age group, and atopic status. The stability of the results was assessed by performing a sensitivity analysis using sequential omission of individual studies. A cumulative meta-analysis was conducted by undertaking sequential pooling, starting with the earliest studies. Funnel plots were performed to estimate the potential publication bias, with an asymmetrical plot suggesting a possible publication bias. The asymmetry was assessed using the Egger's linear regression test and P<0.05 was considered to represent statistically significant publication bias [64]. All statistical tests were performed using STATA 11.0 software (Stata Corporation, College Station, TX). The Bonferroni correction of critical P values for two genetic models was applied when performing a high number of comparisons.

Results

Study characteristics

Fifty studies met the inclusion criteria [7][56]. A flowchart detailing the process for study identification and selection is shown in Figure 1. A study by Undarmaa et al. [51] presented two independent case-control studies, each of which was considered separately for analysis. There were 33 studies of the I50V polymorphism and 35 36 studies of the Q551R polymorphism. Twenty-seven studies were performed in Asians, 19 in Caucasians, two in Mexicans, and one in African Americans. Nineteen studies were performed in adults, and 21 in children. Twelve studies included atopic asthma patients and nine included both atopic and non-atopic asthma patients, but data for these patients could be extracted separately. The quality scores ranged from 5 to 11, suggesting that the methodological quality was generally acceptable. The characteristics of each study are presented in Table 1. Genotype frequencies and HWE examination results are listed in Table 2. Seven studies were not in HWE, and these studies were not included in the meta-analysis.

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Table 1. Characteristics of the case-control studies included in meta-analysis.

https://doi.org/10.1371/journal.pone.0069120.t001

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Table 2. Distribution of IL4RA I50V and Q551R polymorphisms among patients and controls.

https://doi.org/10.1371/journal.pone.0069120.t002

Quantitative data synthesis

IL4RA I50V polymorphism.

Thirty studies investigated the association between the I50V polymorphism and asthma risk. The total sample sizes for case and control groups were 6442 and 7240, respectively. The estimated OR1, OR2 and OR3 values were 1.14 (P = 0.08), 1.09 (P = 0.06), and 1.06 (P = 0.35), respectively (Table 3). These estimates suggested a dominant genetic model; therefore II and IV were combined and compared with VV. The pooled OR was 1.13 (95% CI 1.04–1.23, P = 0.005) (Figure 2). There was no significant heterogeneity (I2 = 5%, P = 0.38). In the stratified analysis by ethnicity, no significant association was found for the studies in Asians (OR = 1.23, 95% CI 1.05–1.45, P = 0.01) or Caucasians (OR = 1.10, 95% CI 0.96–1.26, P = 0.15). In the subgroup analysis by age, the IL4RA I50V polymorphism was not associated with pediatric asthma risk (OR = 1.15, 95% CI 1.03–1.29, P = 0.01) or adult asthma risk (OR = 1.08, 95% CI 0.91–1.27, P = 0.39). In the subgroup analysis according to atopic status, the IL4RA I50 V polymorphism was not significantly associated with the risk of atopic asthma (OR = 1.19, 95% CI 1.01–1.40, P = 0.04) or non-atopic asthma risk (OR = 0.92, 95% CI 0.63–1.35, P = 0.67).

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Figure 2. Meta-analysis for the association between asthma risk and the IL4RA I50V polymorphism.

https://doi.org/10.1371/journal.pone.0069120.g002

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Table 3. Determination of the genetic effects of IL4RA polymorphisms on asthma and subgroup analysis.

https://doi.org/10.1371/journal.pone.0069120.t003

Cumulative meta-analyses were conducted. A tendency toward significant association with asthma risk was found (Figure S1). We performed a sensitivity analysis to evaluate the stability of the meta-analysis. As shown in Figure S2, the statistical significance of the result was not altered when any single study was omitted. The funnel plot did not reveal evidence of obvious asymmetry (Figure S3). The result was further supported by Egger's test (P = 0.601).

IL4RA Q551R polymorphism.

Thirty-two studies identified an association between the IL4RA Q551R polymorphism and asthma risk. A total of 6750 cases and 8594 controls were included in this meta-analysis. The estimated OR1, OR2 and OR3 values were 1.46 (P = 0.002), 1.11 (P = 0.05), and 1.35 (P = 0.002), respectively (Table 3). Thus, these estimates suggested a recessive genetic model; therefore QR and QQ were combined and compared with RR. The pooled OR was 1.46 (95% CI 1.22–1.75, P<0.0001) (Figure 3). No significant heterogeneity was observed (I2 = 16%, P = 0.21). Subgroup analysis was performed by ethnicity. Statistically significant findings were found in Asians (OR = 1.72, 95% CI 1.31–2.25, P<0.0001) but not in Caucasians (OR = 1.09, 95% CI 0.86–1.38, P = 0.48). In the stratified analysis by age group, a statistically significantly increased asthma risk was found among children (OR = 1.50, 95% CI 1.13–1.99, P = 0.005), but no significant risk was found among adult asthmatic patients (OR = 1.36, 95% CI 1.00–1.84, P = 0.05). In terms of atopic status, we found a significant association between this polymorphism and atopic asthma risk (OR = 1.88, 95% CI 1.27–2.79, P = 0.002). However, there was no significant association with non-atopic asthma (OR = 1.90, 95% CI 0.94–3.84, P = 0.07).

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Figure 3. Meta-analysis for the association between asthma risk and the IL4RA R551Q polymorphism.

https://doi.org/10.1371/journal.pone.0069120.g003

Evidence from a cumulative meta-analysis showed that the results were consistent over time (Figure S4). A sensitivity analysis showed no substantial modification of the estimates after exclusion of individual studies (Figure S5). The shape of the funnel plot was symmetrical (Figure S6). Egger's test indicated the absence of publication bias (P = 0.773).

Discussion

On the basis of 50 eligible case-control studies, this meta-analysis comprehensively evaluated the association between the IL4RA I50V and Q551R polymorphisms and asthma risk. In terms of the IL4RA I50 V polymorphism, we found that individuals with the 50I allele (II or IV) showed an increased risk of asthma in the overall population. However, in the subgroup analyses based on ethnicity, age group, and atopic status, no significant associations were observed after Bonferroni correction. A significant association was also noted for the IL4RA Q551R polymorphism. This result suggests that individuals carrying the RR genotype had an increased asthma risk. There is no significant difference in the frequencies of IL4RA Q551R alleles between Asians and Caucasians with asthma (http://asia.ensembl.org); however, analysis stratified by ethnicity showed a significant association with asthma in Asians, but not in Caucasians. It is possible that different lifestyles, diets, and environments may account for this apparent discrepancy. These issues should be investigated in future studies. In the subgroup analysis stratified by age group, the IL4RA Q551R polymorphism was associated with increased pediatric asthma risk. These results demonstrate that even the same variant in the same gene may have a different effect on the pathogenesis and occurrence of asthma in different individuals. To the best of our knowledge, no previous study has assessed the age-specific influence of IL4RA Q551R on asthma risk, and further studies are needed to address the effect of this polymorphism on asthma risk in different age groups. We also carried out a subgroup analysis according to atopic status. There was a significant association between this polymorphism and atopic asthma risk, suggesting that the IL4RA Q551R polymorphism may play a role in the etiology of atopic asthma. IgE-mediated immune responses are best known for their involvement in allergies. Cornejo-García et al. [65] showed that the IL4RA Q551R polymorphism was associated with IgE against prevalent allergens and with total IgE. The IL4RA Q551R polymorphism may therefore be a relevant marker for allergies and atopic asthma development.

IL-4Rα has been shown to play a pivotal role in the pathogenesis of Th2 inflammation and asthma. For example, Kelly-Welch et al. [66] reported that IL-4Rα-deficient mice engrafted with bone marrow derived from IL-4Rα-expressing mice failed to develop goblet-cell metaplasia in response to allergic airway inflammation. In addition, deletion of the gene encoding IL-4Rα rendered mice resistant to the induction of experimental allergic asthma [67]. Mitsuyasu et al. [7] documented that the IL-4Rα 50I variant significantly upregulated the receptor response to IL-4, with resultant increased activation of STAT6, and hence increased cell proliferation and increased IgE production. Furthermore, Rosenwasser et al. [68] showed that peripheral blood mononuclear cells derived from individuals carrying the 551R variant had enhanced IL-4 responsiveness compared with 551Q. It is therefore possible that these two polymorphisms could influence the susceptibility to asthma. The 50I and 551Q variants may be associated with increased asthma risk. The results of this meta-analysis strongly support this hypothesis.

A previous meta-analysis by Loza and Chang has focused on the relationship between these polymorphisms and asthma risk [57], and concluded that the I50 V polymorphism was not significant associated with asthma. However, only six studies of the I50 V polymorphism were included in that meta-analysis. A positive association between this polymorphism and asthma could therefore not be ruled out, because studies with small sample sizes may have had insufficient statistical power to detect any slight effect. Our current meta-analysis included 30 studies (6442 cases and 7240 controls), and found a moderate but significant association. Furthermore, this meta-analysis addressed the methodological issues such as cumulative meta-analysis and sensitivity analysis.

Results from our meta-analysis were stable and reliable. First, sensitivity analyses and cumulative meta-analyses revealed that the results were robust. Second, there was no significant heterogeneity in most of the comparisons. Third, funnel plots and Egger's tests found no significant publication bias. However, some limitations should be addressed. First, the numbers of published studies involving African Americans and Mexicans were limited. Second, the overall outcome was based on unadjusted data, whereas a baseline risk-adjusted analysis could be performed if individual data were available to allow adjustment. Third, asthma is a complex disease with multifactorial etiology. A lack of original data from the eligible studies limited evaluation of the effects of the gene-gene and gene-environment interactions during asthma development. These gene-environment and gene-gene interactions should be further evaluated. Fourth, even though no significant publication bias was found by funnel plot analysis and formal statistical tests, it was impossible to exclude potential publication bias completely, because small studies with null results tend not to be published. Finally, all the studies included in this meta-analysis used a case-control design, which was susceptible to recall and selection biases. In addition, there was a risk of residual confounding by unmeasured factors.

In conclusion, this meta-analysis found significant associations between the IL4RA I50V and Q551R polymorphisms and asthma risk. Further studies in more ethnic groups, especially African Americans and Mexicans, are warranted to validate these results.

Supporting Information

Figure S1.

Cumulative meta-analysis of associations between the IL4RA I50V polymorphism and asthma risk.

https://doi.org/10.1371/journal.pone.0069120.s001

(TIF)

Figure S2.

Sensitivity analysis for the IL4RA I50V polymorphism with asthma risk.

https://doi.org/10.1371/journal.pone.0069120.s002

(TIFF)

Figure S3.

Funnel plot for asthma risk and the IL4RA I50V polymorphism.

https://doi.org/10.1371/journal.pone.0069120.s003

(TIFF)

Figure S4.

Cumulative meta-analysis of associations between the IL4RA R551Q polymorphism and asthma risk.

https://doi.org/10.1371/journal.pone.0069120.s004

(TIF)

Figure S5.

Sensitivity analysis for the IL4RA R551Q polymorphism with asthma risk.

https://doi.org/10.1371/journal.pone.0069120.s005

(TIFF)

Figure S6.

Funnel plot for asthma risk and the IL4RA R551Q polymorphism.

https://doi.org/10.1371/journal.pone.0069120.s006

(TIFF)

Table S1.

Scale for quality assessment of molecular association studies of asthma.

https://doi.org/10.1371/journal.pone.0069120.s007

(DOCX)

Checklist S1.

Checklist of items to include when reporting a systematic review or meta-analysis.

https://doi.org/10.1371/journal.pone.0069120.s008

(DOC)

Acknowledgments

We thank Dr Yungling Leo Lee (Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan) for providing relevant information.

Author Contributions

Conceived and designed the experiments: WN QYX. Performed the experiments: WN JQC. Analyzed the data: WN JQC YSZ. Contributed reagents/materials/analysis tools: WN JQC. Wrote the paper: WN JQC QX YSZ.

References

  1. 1. Masoli M, Fabian D, Holt S, Beasley R (2004) The global burden of asthma: executive summary of the GINA Dissemination Committee report. Allergy 59: 469–478.
  2. 2. Laitinen T, Räsänen M, Kaprio J, Koskenvuo M, Laitinen LA (1998) Importance of Genetic Factors in Adolescent Asthma A Population-based Twin-family Study. Am J Respir Crit Care Med 157: 1073–1078.
  3. 3. Miloux B, Laurent P, Bonnin O, Lupker J, Caput D, et al. (1997) Cloning of the human IL-13Rα1 chain and reconstitution with the IL-4Rα of a functional IL-4/IL-13 receptor complex. FEBS Letters 401: 163–166.
  4. 4. Kotsimbos TC, Ghaffar O, Minshall EM, Humbert M, Durham SR, et al. (1998) Expression of the IL-4 receptor α-subunit is increased in bronchial biopsy specimens from atopic and nonatopic asthmatic subjects. J Allergy Clin Immunol 102: 859–866.
  5. 5. Noben-Trauth N, Shultz LD, Brombacher F, Urban JF, Gu H, et al. (1997) An interleukin 4 (IL-4)-independent pathway for CD4+ T cell IL-4 production is revealed in IL-4 receptor-deficient mice. Proc Natl Acad Sci U S A 94: 10838–10843.
  6. 6. Perkins C, Wills-Karp M, Finkelman FD (2006) IL-4 induces IL-13–independent allergic airway inflammation. J Allergy Clin Immunol 118: 410–419.
  7. 7. Mitsuyasu H, Izuhara K, Mao X-Q, Gao P-S, Arinobu Y, et al. (1998) Ile50Val variant of IL4Rα upregulates IgE synthesis and associates with atopic asthma. Nat Genet 19: 119–120.
  8. 8. Mitsuyasu H, Yanagihara Y, Mao X-Q, Gao P-S, Arinobu Y, et al. (1999) Cutting edge: dominant effect of Ile50Val variant of the human IL-4 receptor α-chain in IgE synthesis. J Immunol162: 1227–1231.
  9. 9. Noguchi E, Shibasaki M, Arinami T, Takeda K, Yokouchi Y, et al. (1999) No association between atopy/asthma and the ILe50Val polymorphism of IL-4 receptor. Am J Respir Crit Care Med 160: 342–345.
  10. 10. Rosa-Rosa L, Zimmermann N, Bernstein JA, Rothenberg ME, Khurana Hershey GK (1999) The R576 IL-4 receptor α allele correlates with asthma severity. J Allergy Clin Immunol 104: 1008–1014.
  11. 11. Heinzmann A, Mao XQ, Akaiwa M, Kreomer RT, Gao PS, et al. (2000) Genetic variants of IL-13 signalling and human asthma and atopy. Hum Mol Genet 9: 549–559.
  12. 12. Sandford AJ, Chagani T, Zhu S, Weir TD, Bai TR, et al. (2000) Polymorphisms in the IL4, IL4RA, and FCERIB genes and asthma severity. J Allergy Clin Immunol 106: 135–140.
  13. 13. Takabayashi A, Ihara K, Sasaki Y, Suzuki Y, Nishima S, et al. (2000) Childhood atopic asthma: Positive association with a polymorphism of IL-4 receptor alpha gene but not with that of IL-4 promoter or Fc receptor I beta gene. Exp Clin Immunol ogenet 17: 63–70.
  14. 14. Hákonarson H, Bjornsdottir US, Ostermann E, Arnason T, Adalsteinsdottir AE, et al. (2001) Allelic frequencies and patterns of single-nucleotide polymorphisms in candidate genes for asthma and atopy in Iceland. Am J Respir Crit Care Med 164: 2036–2044.
  15. 15. Howard TD, Koppelman GH, Xu J, Zheng SL, Postma DS, et al. (2002) Gene-gene interaction in asthma: Il4ra and il13 in a dutch population with asthma. Am J Hum Genet 70: 230–236.
  16. 16. Leung TF, Tang NL, Chan IH, Li AM, Ha G, et al. (2002) Distribution in allele frequencies of predisposition-to-atopy genotypes in Chinese children. Pediatr Pulmonol 34: 419–424.
  17. 17. Mujica-Lopez KI, Flores-Martinez SE, Ramos-Zepeda R, Castaneda-Ramos SA, Gazca-Aguilar A, et al. (2002) Association analysis of polymorphisms in the interleukin-4 receptor (alpha) gene with atopic asthma in patients from western Mexico. Eur J Immunol ogenet 29: 375–378.
  18. 18. Risma KA, Wang N, Andrews RP, Cunningham CM, Ericksen MB, et al. (2002) V75R576 IL-4 receptor alpha is associated with allergic asthma and enhanced IL-4 receptor function. J Immunol 169: 1604–1610.
  19. 19. Beghe B, Barton S, Rorke S, Peng Q, Sayers I, et al. (2003) Polymorphisms in the interleukin-4 and interleukin-4 receptor alpha chain genes confer susceptibility to asthma and atopy in a Caucasian population. Clin Exp Allergy 33: 1111–1117.
  20. 20. Cui T, Wu J, Pan S, Xie J (2003) Polymorphisms in the IL-4 and IL-4R [alpha] genes and allergic asthma. Clin Chem Lab Med 41: 888–892.
  21. 21. Hytonen AM, Lowhagen O, Arvidsson M, Balder B, Bjork AL, et al. (2004) Haplotypes of the interleukin-4 receptor alpha chain gene associate with susceptibility to and severity of atopic asthma. Clin Exp Allergy 34: 1570–1575.
  22. 22. Lee SG, Kim BS, Kim JH, Lee SY, Choi SO, et al. (2004) Gene-gene interaction between interleukin-4 and interleukin-4 receptor alpha in Korean children with asthma. Clin Exp Allergy 34: 1202–1208.
  23. 23. Yang Q, Zou Y, Kuang J (2004) A Study on the Relationship between Interleukin-4 Receptor Polymorphism and Asthma. Acta Academiae Medicinae Jiangxi 144: 37–38.
  24. 24. Isidoro-Garcia M, Davila I, Laffond E, Moreno E, Lorente F, et al. (2005) Interleukin-4 (IL4) and interleukin-4 receptor (IL4RA) polymorphisms in asthma: A case control study. Clin Mol Allergy 29: 15–22.
  25. 25. Hu S, Yang X, Li P, Yu Z (2005) Relation of polymorphism of IL-4 and IL-4R to allergic asthma in children. Chinese Joumal of Medical Laboratory Technology 6: 460–462.
  26. 26. Sun J, Zhang Y, Yu X, Yu J, Chen Y, et al. (2005) A Study on the relationship between IL-4R Q576R polymorphism and child asthma in Haerbing. Lin Chuang Er Ke Za Zhi 28: 138–141.
  27. 27. Bernstein DI, Wang N, Campo P, Chakraborty R, Smith A, et al. (2006) Diisocyanate asthma and gene-environment interactions with IL4RA, CD-14, and IL-13 genes. Ann Allergy Asthma Immunol 97: 800–806.
  28. 28. Kabesch M, Schedel M, Carr D, Woitsch B, Fritzsch C, et al. (2006) IL-4/IL-13 pathway genetics strongly influence serum IgE levels and childhood asthma. J Allergy Clin Immunol 117: 269–274.
  29. 29. Melen E, Umerkajeff S, Nyberg F, Zucchelli M, Lindstedt A, et al. (2006) Interaction between variants in the interleukin-4 receptor alpha and interleukin-9 receptor genes in childhood wheezing: Evidence from a birth cohort study. Clin Exp Allergy 36: 1391–1398.
  30. 30. Deng RQ, Wu B, Chen M (2006) correlation between IL-4R gene polymorphism and asthma. J Clin Intern Med 23: 310–312.
  31. 31. Gui Q, Qian GS, Zhao ZQ, Li SP (2006) Study on association between IL-4R gene mutation and asthmatic patients of Han nationality of Chongqing in China. Chong Qing Yi Xue 35: 2055–2057.
  32. 32. Tang Y, Xu ZH, Wu XQ, Li YQ, Zhou TH (2006) A study on the association between polymorphism of the interleukin-4 receptor alpha gene and bronchial asthma in a population of Han nationality. Zhonghua jie he he hu xi za zhi 29: 440–443.
  33. 33. Battle NC, Choudhry S, Tsai HJ, Eng C, Kumar G, et al. (2007) Ethnicity-specific gene-gene interaction between IL-13 and IL-4Ralpha among African Americans with asthma. Am J Respir Crit Care Med 175: 881–887.
  34. 34. Lopez KI, Martinez SE, Moguel MC, Romero LT, Figueroa CS, et al. (2007) Genetic diversity of the IL-4, IL-4 receptor and IL-13 loci in mestizos in the general population and in patients with asthma from three subpopulations in Mexico. Int J Immunol genet 34: 27–33.
  35. 35. Mak JC, Ko FW, Chu CM, Leung HC, Chan HW, et al. (2007) Polymorphisms in the IL-4, IL-4 receptor alpha chain, TNF-alpha, and lymphotoxin-alpha genes and risk of asthma in Hong Kong Chinese adults. Int Arch Allergy Immunol 144: 114–122.
  36. 36. Zhang H, Zhang Q, Wang L, Chen H, Li Y, et al. (2007) Association of IL4R gene polymorphisms with asthma in Chinese populations. Hum Mutat 28: 1046.
  37. 37. Zhang W, Zhang X, Qiu D, Sandford A, Tan WC (2007) IL-4 receptor genetic polymorphisms and asthma in Asian populations. Resp Med 101: 186–190.
  38. 38. Chan IH, Tang NL, Leung TF, Huang W, Lam YY, et al. (2008) Study of gene-gene interactions for endophenotypic quantitative traits in Chinese asthmatic children. Allergy 63: 1031–1039.
  39. 39. De Faria ICJ, De Faria EJ, Toro AADC, Ribeiro JD, Bertuzzo CS (2008) Association of TGF-beta1, CD14, IL-4, IL-4R and ADAM33 gene polymorphisms with asthma severity in children and adolescents. Jornal de Pediatria 84: 203–210.
  40. 40. Xiaomin L, Fenglin C, Jianmin H, Yuzhi S, Binsheng G, et al. (2008) Correlation between genetic polymorphism of cytokine genes, plasma protein levels and bronchial asthma in the Han people in northern China. J Asthma 45: 583–589.
  41. 41. Trajkov D, Mirkovska-Stojkovikj J, Arsov T, Petlichkovski A, Strezova A, et al. (2008) Association of cytokine gene polymorphisms with bronchial asthma in Macedonians. Iran J Allergy Asthma Immunol 7: 143–156.
  42. 42. Sun YL, Kong LF, Wang Y (2008) Relationship between Q576R IL-4 Receptor α Allele or CCR5Δ32 Mutation and Asthma. Journal of China Medical University 37: 545–547.
  43. 43. Amirzargar AA, Movahedi M, Rezaei N, Moradi B, Dorkhosh S, et al. (2009) Polymorphisms in IL4 and IL4RA confer susceptibility to asthma. J Investig Allergol Clin Immunol 19: 433–438.
  44. 44. Llanes E, Quiralte J, Lopez E, Sastre B, Chacartegui M, et al. (2009) Analysis of polymorphisms in olive pollen allergy: IL13, IL4RA, IL5 and ADRB2 genes. Int Arch Allergy Immunol 148: 228–238.
  45. 45. Wang J-Y, Liou Y-H, Wu Y-J, Hsiao Y-H, Wu LS-H (2009) An association study of 13 SNPs from seven candidate genes with pediatric asthma and a preliminary study for genetic testing by multiple variants in Taiwanese population. J Clin Immunol 29: 205–209.
  46. 46. Xu Y, Song L, Dang L, Lin S (2009) Polymorphism of IL-4 receptor gene in patients with childhood wheezing. Chin J Gen Pract 8: 565–567.
  47. 47. Beghe B, Hall IP, Parker SG, Moffatt MF, Wardlaw A, et al. (2010) Polymorphisms in IL13 pathway genes in asthma and chronic obstructive pulmonary disease. Allergy 65: 474–481.
  48. 48. Berce V, Potocnik U (2010) Association of Q551R polymorphism in the interleukin 4 receptor gene with nonatopic asthma in Slovenian children. Wien Klin Wochenschr 122: 11–18.
  49. 49. Bottema RW, Nolte IM, Howard TD, Koppelman GH, Dubois AE, et al. (2010) Interleukin 13 and interleukin 4 receptor-alpha polymorphisms in rhinitis and asthma. Int Arch Allergy Immunol 153: 259–267.
  50. 50. Michel S, Liang L, Depner M, Klopp N, Ruether A, et al. (2010) Unifying candidate gene and GWAS Approaches in Asthma. PLoS One 5: e13894.
  51. 51. Undarmaa S, Mashimo Y, Hattori S, Shimojo N, Fujita K, et al. (2010) Replication of genetic association studies in asthma and related phenotypes. J Hum Genet 55: 342–349.
  52. 52. Wu X, Li Y, Chen Q, Chen F, Cai P, et al. (2010) Association and gene-gene interactions of eight common single-nucleotide polymorphisms with pediatric asthma in middle China. J Asthma 47: 238–244.
  53. 53. Fan C, Liu Y, Ma Y, Zhang W (2010) Susceptibility gene polymorphismand bronchial asthma. Progress in Modern Biomedicine 10: 3264–3267.
  54. 54. Genome Medicine Database of Japan (GeMDBJ). (2010) Available: https://gemdbj.nibio.go.jp/dgdb/.
  55. 55. Murk W, Walsh K, Hsu LI, Zhao L, Bracken MB, et al. (2011) Attempted replication of 50 reported asthma risk genes identifies a SNP in RAD50 as associated with childhood atopic asthma. Hum Hered 71: 97–105.
  56. 56. Su MW, Tung KY, Liang PH, Tsai CH, Kuo NW, et al. (2012) Gene-gene and gene-environmental interactions of childhood asthma: a multifactor dimension reduction approach. PLoS One 7: e30694.
  57. 57. Loza MJ, Chang BL (2007) Association between Q551R IL4R genetic variants and atopic asthma risk demonstrated by meta-analysis. J Allergy Clin Immunol 120: 578–585.
  58. 58. Thakkinstian A, McEvoy M, Minelli C, Gibson P, Hancox B, et al. (2005) Systematic review and meta-analysis of the association between β2-adrenoceptor polymorphisms and asthma: a HuGE review. Am J Epidemiol 162: 201–211.
  59. 59. Thakkinstian A, McElduff P, D'Este C, Duffy D, Attia J (2005) A method for meta-analysis of molecular association studies. Stat Med 24: 1291–1306.
  60. 60. Nie W, Chen J, Xiu Q (2012) Cytotoxic T-Lymphocyte Associated Antigen 4 Polymorphisms and Asthma Risk: A Meta-Analysis. PLoS One 7: e42062.
  61. 61. Nie W, Fang Z, Li B, Xiu Q (2012) Interleukin-10 promoter polymorphisms and asthma risk: A meta-analysis. Cytokine 60: 849–855.
  62. 62. Nie W, Liu Y, Bian J, Li B, Xiu Q (2013) Effects of Polymorphisms-1112C/T and+ 2044A/G in Interleukin-13 Gene on Asthma Risk: A Meta-Analysis. PLoS One 8: e56065.
  63. 63. Nie W, Zhu Z, Pan X, Xiu Q (2013) The interleukin-4 -589C/T polymorphism and the risk of asthma: A meta-analysis including 7345 cases and 7819 controls. Gene 520: 22–29.
  64. 64. Egger M, Smith GD, Schneider M, Minder C (1997) Bias in meta-analysis detected by a simple, graphical test. BMJ 315: 629–634.
  65. 65. Cornejo-García JA, Guéant-Rodriguez RM, Torres MJ, Blanca-Lopez N, Tramoy D, et al. (2012) Biological and genetic determinants of atopy are predictors of immediate-type allergy to betalactams, in Spain. Allergy 67: 1181–1185.
  66. 66. Kelly-Welch AE, Melo ME, Smith E, Ford AQ, Haudenschild C, et al. (2004) Complex role of the IL-4 receptor α in a murine model of airway inflammation: expression of the IL-4 receptor α on nonlymphoid cells of bone marrow origin contributes to severity of inflammation. J Immunol 172: 4545–4555.
  67. 67. Grünig G, Warnock M, Wakil AE, Venkayya R, Brombacher F, et al. (1998) Requirement for IL-13 independently of IL-4 in experimental asthma. Science 282: 2261–2263.
  68. 68. Rosenwasser L, Klemm D, Dresback J, Inamura H, Mascali J, et al. (1995) Promoter polymorphisms in the chromosome 5 gene cluster in asthma and atopy. Clin Exp Allergy 25: 74–78.