Cross-reactivity between Cupressus arizonica and Cupressus sempervirens pollen extracts

Background: Cupressus arizonica and C. sempervirens, two species belonging to the Cupressaceae family, are recognized as an important cause of respiratory allergies in countries with a Mediterranean climate. Objective: The relationship between pollen extracts from these two species was studied by evaluating the reactivity with polyclonal rabbit antisera and human IgE. Methods: The two extracts were analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Cross-reactivity was evaluated by ELISA and immunoblotting inhibition experiments. Results: The electrophoretic patterns of the two extracts are quite different, although some components display identical molecular weights. The immunoblotting developed with human IgE from subjects allergic to members of the Cupressaceae family indicated that two major IgE-reactive components, displaying molecular weights of about 43,000 and 36,000 d, were similarly detected in both extracts. Inhibition experiments showed a high degree of cross-reactivity between the two extracts when tested with rabbit polyclonal antibodies against C. arizonica and C. sempervirens. When tested with human IgE inhibition methods, both extracts were able to reciprocally inhibit all of the IgE-reactive bands, although C. arizonica extract was always a better inhibitor. Conclusions: C. arizonica and C. sempervirens extracts are highly cross-reactive at the IgE level and share a number of common epitopes also identified by polyclonal rabbit antisera.