It has previously been shown that various inflammatory diseases, such as diabetes mellitus, bronchial asthma, chronic inflammatory bowel diseases, and rheumatoid arthritis, are in some circumstances genetically linked to the same chromosomal regions. Consequently, common genes underlying the pathogenetics of these diseases have been proposed. Chronic inflammatory disorders can be subdivided by their predominant immune response, either TH1 or TH2. For example, juvenile idiopathic arthritis (JIA) is a TH1 disease, and bronchial asthma is a TH2 disease.
The present study investigated the polymorphism Arg110Gln within the IL13 gene, a strong TH2 cytokine. We attempted to determine whether it is associated with these 2 diseases and whether this would reflect the TH1/TH2 paradigm.
Arg110Gln was typed in 4 different populations: asthmatic children, atopic children, children with JIA, and a control population. Statistical analysis was performed by using logistic and linear regression analysis of serum IgE levels and the Armitage trend test.
The variant Gln110 was shown to be associated with increased total serum IgE levels in our atopic population (P =.006) and was weakly associated with bronchial asthma (P =.04). There was no association of the variant with JIA when compared with the control population. However, the variant Gln110 was significantly less frequent in children with JIA compared with its presence in children with bronchial asthma (P =.007).
This is the first study to compare the same gene variant in TH1 and TH2 chronic inflammatory diseases. The results suggest that the same gene variant might protect from one disease and make an individual susceptible to the other.