Background: IL-4 receptor alpha chain is crucial for the binding and signaling of IL-4, which mediates isotype switching and IgE production. The gene of IL-4 receptor alpha chain is a candidate gene for asthma and atopy.
Objectives: To determine whether Ile50Val and Q576R polymorphisms of IL-4 receptor alpha chain gene were associated with asthma and higher level of total IgE in Chinese, Malay and Indian populations.
Methods: About 303 physician-diagnosed asthmatic subjects (145 Chinese, 73 Malay, 85 Indian) and 355 unselected blood donors (157 Chinese, 98 Malay, 100 Indian) were recruited. Total serum IgE level was measured by ELISA. Genotypes of Ile50/Val and Q576R were determined by PCR and restriction enzyme length polymorphism (RFLP).
Results: Ile50Val heterozygote is less frequent in asthmatics than in controls in Malay population (P=0.007). No difference was found in Chinese and Indian population. Ile50/Ile50 was more prevalent in higher total serum IgE group (IgE>100IU/ml) in Malay. The prevalence of Ile50/R576 haplotype was lower in asthmatics than controls in Chinese (P=0.046); while the prevalence of Ile50/Q576 haplotype was lower in asthmatics than in controls in Malay (P=0.048). The frequencies of the two single nucleotide polymorphisms (SNPs) and haplotypes vary among ethnicities (P<0.05).
Conclusion: IL-4RA gene polymorphisms and its haplotypes showed ethnic variations. The association between IL-4RA gene polymorphisms, its haplotypes and asthma differed from ethnicities.