| Objective: To investigate the correlations of transforming growth factor(TGF)-β1 promoter polymorphism C-509T with the phenotype and severity of asthma, and the relationship between TGF-β1 gene promoter polymorphism C-509T and the serum protein levels of TGF-β1 in asthmatics. Methods: Sixty asthmatics and thirty healthy control subjects were studied. The TGF-β1 promoter polymorphism C-509T was detected with the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The serum protein levels of TGF-β1 were examined with the sandwich enzyme-linked immunosorbent assay (ELISA) method. Results: (1) There were three genotypes (CC, CT, TT) in the TGF-β1 promoter region C-509T in the asthmatics and the healthy control subjects. The genotype frequencies between the asthmatics and the healthy control subjects were significantly different (χ2=4.35, P<0.05). The T allele frequencies in the asthmatics and in the healthy control subjects were 41.7% and 25.0%, respectively, with significant difference (χ2=4.82, P<0.05), indicating that the presence of the T allele was associated with the phenotypes of asthma. (2) There was no significant difference in the genotypes or alleles of the TGF-β1 promoter locus -509 between the severe asthmatics and the mild asthmatics (χ2=1.67, P>0.05; χ2=0.13, P>0.05, respectively). (3) The serum total protein levels of TGF-β1 were significantly different in the genotypes of the TGF-β1 promoter region locus -509 in the asthmatics (F=6.72, P<0.01). The serum TGF-β1 protein levels in the genotype TT was higher than other two genotypes (q1=4.00, P<0.01 vs CT; q2=5.00, P<0.01 vs CC), but no significance was found in the serum protein levels of TGF-β1 between the genotypes CT and CC(q3=0.82, P>0.05). Conclusions: This study indicates that the TGF-β1 promoter polymorphism C-509T is associated with the asthma phenotypes, and the serum protein levels of TGF-β1 in the asthmatic group, but probably not associated with the asthma severity.
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