Association of TNF-alpha -308 G/A and IL-4 -589 C/T gene promoter polymorphisms with asthma susceptibility in the south of Iran.

Both tumor necrosis factor alpha (TNF-alpha) and interleukin (IL) 4 have been implicated in the pathogenesis of asthma. Furthermore, a G/A substitution at position -308 of the TNF-alpha gene promoter and a C/T substitution at position -589 of the IL-4 gene promoter have been associated with increased production of TNF-alpha and IL-4, respectively. The aim of the present study was to analyze the association between TNF-alpha-308 G/A and IL-4-589 C/T polymorphisms and susceptibility to asthma in a group of patients from southern Iran. We analyzed the frequency of TNF-alpha -308 G/A and IL-4-589 C/T polymorphisms in a total of 203 asthmatic patients compared to 113 nonasthmatic control subjects. An association was observed between the TNF-alpha -308 G/A polymorphism and susceptibility to asthma in patients with a ratio between forced expiratory volume in 1 second and forced vital capacity of less than 75% compared with normal subjects; however, the association did not achieve statistical significance (P = .054). The IL-4-589 C/T polymorphism was associated with asthma susceptibility (P = .02). In addition, the association between this polymorphism and asthma severity approached statistical significance (P = .07). These results provide further evidence for a role of TNF-alpha-308 G/A and IL-4-589 C/T polymorphisms in susceptibility to and severity of asthma. Further studies involving a larger number of patients may help to confirm our observations.