Asthma is a complex polygenic disease in which gene-environment interactions are important. The gene encoding tumour necrosis factor alpha (TNFalpha) is one of several candidate loci for asthma pathogenesis and is highly polymorphic. A number of studies have investigated the polymorphism of TNFalpha-308 gene promoter (substitution G-->A, designated as TNF1 and TNF2) in relation to asthma susceptibility in different populations. However, the results of individual studies have been inconsistent.
