Allelic association of gene markers on chromosome 11q in Italian families with atopy

In our study, the genetic linkage of the Fc epsilon RI beta gene with atopy in 77 affected sibling pairs recruited from an Italian panel of 201 subjec ts has been examined. Atopy was defined by the presence of a positive skin prick test to one or more common aeroallergens, a positive RAST test to one or more common aeroallergens and an elevated circulating total IgE. Genoty pe analysis was performed by PCR amplification of Fc epsilon RI beta CA and CI11-319 CA microsatellites. All the family members were also tested for t he Il epsilon 181 mutation with the ARMS method and for Leu181/Leu183 polym orphism. Seventy-two point five percent (72.5%) of the affected sibling pai rs shared their maternal allele and 27.5% did not. Therefore, an increased maternal allele sharing was observed: chi(2) = 8.10, p < 0.01. Comparing pa ternal versus maternal allele sharing, a significant difference was observe d for the C1II-319 CA marker (chi(2) = 4.32, p < 0.05). Atopy phenotype wit h positive skin prick test, RASTs, and high total serum IgE also showed gre ater sharing of maternal than paternal alleles in affected sibling pairs. O f the 201 subjects studied, 17 (8.4%) were positive for Leu181. Ten of thes e were children and seven (70%) had inherited the variant maternally. The s even children had maternally inherited Leu181/Leu183 and were atopic. Withi n this sample the maternal inheritance of Fc epsilon RI beta Leu181/Leu183 was associated with an increased risk of IgE responses to common allergens, raised eosinophil counts and increased skin prick test reactions. Therefor e, the variant identified a genetic risk factor for atopy. Conclusion: The central role of Fc epsilon RI beta in atopy and the linkage data presented here point to the possibility that genetic variation in Fc epsilon RI beta or its controlling element may cause differences in the ext ent of IgE responses between atopic and non-atopic subjects. A search for s uch mutations or polymorphisms will need to take into account some carriers of atopy among the normal population; and genetic heterogeneity among atop ic individuals.