Cross-reactivity of Olea europaea with other Oleaceae species in allergic rhinitis and bronchial asthma.

Cross-reactivity between pollen extracts of four species of Oleaceae was studied: olive (Olea europaea), ash (Fraxinus excelsior), privet (Ligustrum vulgare), and lilac (Syringa vulgaris). Thus, 51 patients and 13 atopic controls were studied, by means of intracutaneous skin tests, histamine-release tests against the four extracts, and specific IgE to O. europaea. The proteic content of the four extracts was assessed by SDS-PAGE and immunoblotting, and similarity of all the extracts studied was observed after electrophoresis and immunodetection. Six common bands were found to be responsible for the cross-reactivity, with apparent molecular weights of 49.6, 40, 36.7, 19.7, 16.7, and 14 kDa, respectively. The cross-reactivity was also corroborated by immunoblotting inhibition and FEIA inhibition. The patients had a similar response to the four allergenic extracts used, although the response to Olea was greatest. When the patients were compared by their geographic origin (northern or southern Spain, according to the distribution of areas of olive pollen influence), there were no significant differences between the two groups in skin reactivity, but a higher histamine release was observed for the four extracts in the southern group, although it was significant only for Fraxinus and Ligustrum. This work corroborated the practicality of the diagnostic methods used and the cross-reactivity between the four species studied, as demonstrated by the different methods used. Therefore, we suggest that only O. europaea extract be used in diagnosis and immunotherapy in Oleaceae pollen allergy.