Interleukin-4 gene promoter polymorphism [C590T] and asthma in Kuwaiti Arabs

Background: Recent studies have demonstrated an association of the T allele of a promoter polymorphism [C590T] of interleukin-4 (IL-4) gene with asthma/atopy in the US and Japanese populations, but data from the UK and Australian families failed to find an association. We have investigated the association of this [C590T] promoter polymorphism in Kuwaiti Arabs with asthma.

Methods: This study included 184 subjects (84 asthmatics and 100 non-asthmatics, 47 of whom were totally unrelated normal healthy controls with no history of asthma/atopy in three generations of near relatives). The [C590T] promoter polymorphism of the IL-4 gene was analyzed by a polymerase chain reaction-restriction fragment length polymorphism method using the restriction enzyme AvaII.

Results: The frequency of the T allele was found to be 0.79 in asthmatics, 0.75 in non-asthmatic first-degree relatives and 0.76 in unrealted controls in Kuwaiti Arabs. No significant difference was detected in the distribution of the three genotypes (TT, CT and CC) between the asthmatic, non-asthmatic relatives and the unrelated controls. The incidence of co-existing phenotypes e.g. hay fever, eczema and a positive skin prick test was significantly higher in asthmatics than in the non-asthmatics irrespective of the [C590T] genotype. However, within the asthmatic group, a higher incidence of eczema was detected in asthmatics with a heterozygous CT genotype compared to the asthmatics with a TT genotype.

Conclusions: Our results do not show an association between [C590T] promoter polymorphism of the IL-4 gene and asthma in Kuwaiti Arabs. Our results are in keeping with the reports from the UK and Australian families (no association) but in contrast to the findings from US and Japanese populations (an association reported).