Polymorphisms of the IL12B, IL1B, and TNFA Genes and Susceptibility to Asthma

Background: Asthma is one of the most common chronic inflammatory diseases in developed countries. Susceptibility to asthma is associated with interaction between multiple genes and environmental factors. Several cytokines play a major role in the pathophysiology of the disease. Objective: We analyzed the distribution of cytokine gene polymorphisms in a group of patients with asthma and a control group in order to determine the effect of these variants, or their combinations, on the development of clinical phenotypes. Methods: We genotyped 22 single-nucleotide polymorphisms (SNPs) corresponding to 13 cytokine genes (IFNG, IL1A, IL1B, IL1R1, IL1RN, IL2, IL4, IL4R, IL6, IL10, IL12B, TGFB1, and TNFA) in 376 individuals (219 asthmatic patients and 157 controls). Genetic association was evaluated using genotype and allele models for different asthma phenotypes. Gene gene interactions were explored using multifactor dimensionality reduction. Results: Genotype AC of IL12B -1188 was associated with the presence of asthma. A significant association was detected between 2 SNPs analyzed in TNFA (-308 and 238) and atopic asthma and severe-persistent asthma. The IL1B TT haplotype (39621 and -511T) was also associated with atopy and moderate-persistent asthma. Conclusion: Our data show that the presence of SNPs in IL12B,TNFA, and IL1B was significantly associated with asthma, atopy, and severity of asthma. We also highlight the importance of genetic context, haplotype, and gene gene interaction analysis in genetic association studies.