LIMITED GENETIC-CONTROL OF SPECIFIC IGE RESPONSES TO RYE GRASS-POLLENALLERGENS IN AUSTRALIAN TWINS

Background Both genetic and environmental factors are thought to contr ibute to specific IgE responses, however, the relative contribution of each in the responses to individual ryegrass pollen allergens is larg ely unknown even though some responses to allergens have been linked t o certain HLA complexes. Objective Using a large group of monozygotic and dizygotic twins, this study designed to investigate the IgE bindin g profiles of individual ryegrass pollen (Lolium perenne) components t o assess the relative contribution of genetic and environmental factor s in determining IgE responses to specific allergens. Methods Ryegrass pollen proteins were separated by electrophoresis and immunoblotted w ith sera from 191 pairs of twins where at least one sibling had a SPT > 2 mm to perennial ryegrass. Concordance levels for individual ryegra ss pollen components were compared between monozygotic and dizygotic t wins in a subset group where both twins had SPT > 3 mm to perennial ry egrass. Results Immunoblotting revealed 23 individual IgE-binding comp onents from ryegrass pollen, Although there was a significantly greate r proportion of monozygotic twins with SPT wheals greater than 3 mm wh en compared with the dizygotic twins, the mean case-wise concordance f or the immunoblot components was similar for both groups of twins. The mean case-wise concordance when at least four pairs of sera were invo lved was 44% for the MZ twins (n = 11 components) and 45% for the DZ t wins (n = 12 components). We found no significant differences in conco rdance levels for any of the 23 individual components including allerg ens previously-associated with HLA. Conclusion Evidence for genetic co ntrol of allergen-specific IgE responses in a large population sample of twins to individual ryegrass allergens is limited, indicating that the ISE responses to specific ryegrass pollen allergens are determined largely by environmental factors.