The C-509T Promoter Polymorphism of the Transforming Growth Factor Beta-1 Gene Is Associated with Levels of Total and Specific IgE in a Colombian Population

Abstract

Background: The C-509T polymorphism of the transforming growth factor beta-1 (TGFB1) gene has been associated with asthma and asthma-related phenotypes, but its influence on total and specific IgE levels is controversial. Objective: To investigate the association between C-509T and asthma, as well as total IgE and specific IgE against Blomia tropicalis and Dermatophagoides pteronyssinus, in a Colombian population. Methods: The study population consisted of 417 asthmatics, 390 controls and 116 nuclear families. The C-509T polymorphism was genotyped using single-base extension minisequencing or Taq Man probes. IgE and TGFβ1 levels were measured by ELISA. Regression analysis and family-based association tests were performed in cases/controls and families. Associations were corrected by population structure using a panel of 52 ancestry informative markers in the case-control dataset. Results: There was no association between C-509T and asthma. In asthmatics, the CC genotype was associated with higher total IgE levels compared with the other genotypes [mean IgE: 2.81 ± 0.42 vs. 2.71 ± 0.45 log IU/ml; p = 0.016, corrected p value (p_c) = 0.019]. When only atopic asthmatics were included, the significance remained (p = 0.02, p_c = 0.03). In the family-based analyses, the C allele was associated with higher total IgE levels (p = 0.02) and the CC genotype with specific IgE to D. pteronyssinus (p = 0.01). Conclusions: C-509T is associated with total IgE levels and specific IgE to D. pteronyssinus in asthmatic patients. In contrast to other studies, we found the CC genotype to be associated with higher levels of total and specific IgE. Differences in the frequency of this allele among populations could alter its effects as a risk factor for asthma-associated phenotypes.