Lack of linkage between chromosome 5q23-33 markers and IgE/bronchial hyperreactivity in 67 Scottish families

Background Raised serum immunoglobulin E (IgE) and bronchial hyperreactivit y (BHR) are risk factors for the expression of the asthma phenotype. Previo us studies have reported evidence for linkage between these traits and mark ers on the 5q23-33 cytokine gene cluster. Objective To test for linkage between total serum IgE/BHR and microsatellit e markers which map to the 5q23-33 region in an ethnically distinct cohort of families from Aberdeen, Scotland. Methods We performed a linkage study between five polymorphic markers (span ning the chromosome 5q23-33 region) and total serum IgE and BHR traits. A c ohort of 67 families, who were recruited originally to study the natural hi story of wheeze, were clinically characterized and genotyped for D5S404, IL 4, IRF-1, IL9, D5S436 markers. Linkage analyses were performed using the no nparametric Haseman-Elston algorithm for the quantitative trait log IgE, an d the nonparametric LOD score (NPL-score) of the GENE-HUNTER package for th e qualitative traits serum IgE and BHR. Results The results of the nonparametric linkage analysis using either the Haseman-Elston algorithm or NPL-score were consistent and showed no evidenc e for linkage with IgE. There was also no evidence for linkage between the BHR traits (at cut-off values of PD20FEV(1) < 8 mmol and 16 mmol) and any o f the tested five microsatellite markers. Conclusions This study presents evidence against the presence of a gene wit h a major effect on total serum IgE or BHR in the 5q23-33 region, in this e thnic group.