Relationship between polymorphisms in IL4 and asthma in Japanese women: the Kyushu Okinawa Maternal and Child Health Study.

BACKGROUND Interleukin (IL) 4 plays a critical role in immune responses by acting as a growth factor for type 2 helper T cells and inducing immunoglobulin (Ig) class switching to IgE. Epidemiological evidence of the relationship between single-nucleotide polymorphisms (SNPs) in IL4 and asthma is inconsistent. OBJECTIVES We examined the association between the IL4 SNPs rs2243250, rs2070874, rs2227284, and rs2243290 and asthma in young adult Japanese women. METHODS The study population comprised 89 women who met the criteria of the European Community Respiratory Health Survey (ECRHS) for asthma. The control group comprised 1281 nonasthmatic women (ECRHS criteria) who had not been diagnosed with asthma by a physician. Adjustment was made for age, region of residence, presence of older siblings, smoking, and education. RESULTS Compared with the AA genotype of rs2243290, the AC genotype, but not the CC genotype, was significantly associated with a reduced risk of asthma: the adjusted odds ratio for the AC genotype was 0.62 (95% CI, 0.39-0.996). No evident relationships were found between rs2243250, rs2070874, or rs2227284 and asthma. None of the haplotypes were significantly associated with asthma. No significant interactions were found between the 4 SNPs under study and smoking with respect to the risk of asthma. CONCLUSIONS Ours is the first study in a non-Western population to show that the IL4 SNP rs2243290 was significantly associated with the risk of asthma. Smoking did not significantly modify the gene-disease associations under study.