Single nucleotide polymorphism genotyping
Genomic DNA was obtained from the peripheral blood of the participants using the Gentra Puregene Blood kit (Qiagen Sciences, Germantown, MD, USA) with consent of the participant’s parents. The genotyping of IL-13 (rs20541), CD14 (rs2569190), TLR4 (rs1927911), and GSTP1 (rs1695) SNPs was performed by TaqMan fluorogenic 5’ nuclease assay (ABI, Foster City, CA, USA), in accordance with the manufacturer’s instructions. Duplicate samples and negative controls were included to ensure genotyping accuracy. Details are described in a previous study.1,13,23