Background: Both tumor necrosis factor α (TNF-α) and interleukin (IL) 4 have been implicated in the pathogenesis of asthma. Furthermore, a G/A substitution at position -308 of the TNF-α gene promoter and a C/T substitution at position –589 of the IL –4 gene promoter have been associated with increased production of TNF-α and IL-4, respectively.

Objective: The aim of the present study was to analyze the association between TNF-α -308 G/A and IL-4 -589 C/T polymorphisms and susceptibility to asthma in a group of patients from southern Iran.

Methods: We analyzed the frequency of TNF- α -308 G/A and IL-4 -589 C/T polymorphisms in a total of 203 asthmatic patients compared to 113 nonasthmatic
control subjects.

Results: An association was observed between the TNF-α –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).

Conclusion: These results provide further evidence for a role of TNF-α -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 confi rm our observations.

Key words: Asthma. Interleukin-4. Tumor necrosis factor-α. Polymorphism.