Background Polymorphisms within the β subunit of the high-affinity receptor for IgE (FcεR1-β) on chromosome 11q13 have been related to atopy and asthma and the lymphotoxin α (LTα) gene on chromosome 6 is implicated in asthma.
Objective To elucidate the association of polymorphisms in the FcεR1-β and LTα genes to IgE responses and asthma in a family-orientated rural population.
Methods A total of 461 adult farmers, who participated in an epidemiological follow-up study on respiratory symptoms among farmers on the Swedish island of Gotland, were examined. The traits assessed included serum total IgE, IgE antibody responses to 21 common inhalant allergens and asthma.
Results The 237G mutation was only detected in seven persons. Atopy was found to be associated with the RsaI-ex7 AB-genotype (OR = 1.9; P = 0.04). The RsaI-ex7 B allele had a significant influence on IgE responses to pollens and dust mites (OR = 5.5; P = 0.03 and OR = 5.2; P = 0.049, respectively). The influence of this allele was stronger when the association towards single dust mite species (Lepidoglyphus destructor) was estimated (OR = 7.1, P = 0.03) and the association increased even more when the major allergen of L. destructor (rLep d 2) was analysed (OR = 11.2, P = 0.02). These associations were independent of sex, age and smoking, and the estimates of RsaI-in2 independent of RsaI-ex7. RsaI-in2, RsaI-ex7 and LTα genotypes were unassociated with total serum IgE. No significant difference in the distribution of RsaI-in2, RsaI-ex7 and LTα genotypes was found among subjects with atopy or asthma compared to healthy controls.
Conclusion This study supports the notion that polymorphisms in the FcεR1-β gene have significant effects on IgE responsiveness. Secondly, dust mites in rural populations influence the expression of genes on chromosome 11q13.