Antigenic and allergenic differences between 16 different cultivars of Olea europaea.

Abstract

In southern Spain, during the months of May and June, most of the air-borne pollen is from olive trees. However, in inland regions, such as Madrid, there exist many atopic patients who exhibit positive reactions to pollen of gramineae and reactivity to Olea europaea pollen. It is remarkable that only a few of them are exclusively reactive to Olea europaea (monosensitized), in contrast to southern zones, in which we found an increase in monosensitization (1). In 1984, Gonzalez Quevedo in our department began to study Olea europaea pollen from different cultivars. Using both in vitro and in vivo techniques, we found statistically significant differences in allergenic activity and potency between the different varieties. Direct RAST and skin tests revealed greater allergenic activity in extracts of the varieties cornezuelo, cornicabra, gordal, ojiblanco, manzanilla, and verdial when compared with the other varieties studied. In addition, we confirmed that the major allergen of Olea europaea pollen has an isoelectric point with value close to 6. This major antigen is present in all the analysed extracts from the distinct 16 cultivars, and we found that the allergenic reactivity increased in parallel with the increase in content of this antigen (2). Cross-reactivity, caused by the presence of allergenic fractions common to extracts of different origin, has been widely studied using inhibition RAST and, less frequently, by CRIE (radioimmunoelectrophoresis) and reverse enzymoimmunoassay. Bousquet et al. studied the cross-reactivity between four types of Oleaceae (Olea europaea, Fraxinus excelsior, Ligustrum vulgare, and Phillyria angustifolia) using inhibition RAST, isoelectrofocusing, and tandem crossed immunoelectrophoresis (CIE). They detected a high degree of cross-reactivity but not a total identity between these four pollen species (3). In 1992, Baldo et al. studied the cross-reactivity between olive and privet pollens, with olive pollen having major antigens between 18 and 19 kDa, 20 kDa, and 40 kDa, while pollens in privet were in the range of 19, 20, and 40 kDa. Baldo et al. concluded that the presence of IgE antibodies that react with the pollen may not necessarily be a consequence of the sensitization to the pollen of these species (4). In 1984, our group studied 16 cultivars of Olea europaea from the botanical and agronomic point of view (5–14). This comprised a biological evaluation in vivo and in vitro, and a study of the protein content of the pollen extracts, aimed at establishing whether there are distinctive characteristics among the different cultivars.