Polymorphisms in the IL-4, IL-4 receptor α chain, TNF-α, and lymphotoxin-α genes and risk of asthma in Hong Kong Chinese adults

Abstract

Background: Susceptibility to the development of asthma and other atopic diseases is known to be associated with genetic components. However, association studies with interleukin-4 (IL-4), IL-4 receptor α subunit (IL-4Rα), tumor necrosis factor-α (TNF-α) and lymphotoxin-α (LT-α) genes were inconclusive, as both positive and negative results were obtained in several populations studied. We aimed to investigate the association of the polymorphisms for IL-4 (C-589T), IL-4Rα (Gln576Arg), TNF-α (G-308A) and LT-α (A252G) genes as candidates and asthma in adult Hong Kong Chinese population. Methods: The association study was conducted in an age- and smoking status-matched case-control design in asthma patients (n = 292) and healthy controls (n = 292) using polymerase chain reaction and restriction fragment length polymorphism. Results: No significant differences were found in allele and genotype frequencies of all four genes between patients and controls. After stratification by atopic status, the heterozygous AG genotype of LT-α (A252G) was found to increase risk of asthma in atopic population [odds ratio (OR) = 2.00, 95% CI 1.09-3.67, p = 0.024]. When stratified by smoking status, we found increased risk of asthma with subjects carrying the heterozygous AG and homozygous GG genotypes of LT-α in ever-smokers (OR = 2.73, 95% CI 1.11-6.69, p = 0.028 for heterozygotes; OR = 3.34, 95% CI 1.16-9.62, p = 0.026 for homozygotes). Conclusion: Our results suggest that the variability of LT-α genotypes may have potential implications for individual susceptibility to asthma in atopic or in ever-smoking Chinese adults in Hong Kong. Copyright © 2007 S. Karger AG.