Allergy to date fruits:: characterization of antigens and allergens of fruits of the date palm (Phoenix dactylifera L.)

Background: Date-palm (Phoenix dactylifera L,) fruits are eaten daily by most inhabitants of the Middle East and the neighboring countries. Recent reports have indicated that dates are allergenic. This study aimed to investigate the antigenic and allergenic potential of date fruits. Methods: Date-fruit extracts from eight cultivars were evaluated in skin prick tests (SPT) in an atopic population, used to produce antisera, analyzed by SDS-PACE, and fractionated by gel-filtration chromatography, Sera from SPT-positive individuals were evaluated by ELISA and RAST, and in anti-IgE immunoblot experiments. Results: About 13% of patients were SPT-positive for at least two extracts. SDS-PACE of whole extracts revealed 15-18 protein bands of 6.5->100 kDa, and Sephacryl S-200 fractions gave distinct peptide bands, RAST and anti-IgE ELISA gave a range of positive results, which could be abrogated when sera were preabsorbed with fruit extracts. IgE immunoblots of different extracts with pooled positive sera revealed different anti-IgE-binding immunoprints. All the positive sera from fruit-allergic and pollen-allergic individuals bound strongly to two anti-IgE reactive bands of 6.5 to 12-14 kDa and 28-33 kDa, respectively, and about 50% of sera bound to a 54-58-kDa band, Conclusions: These results strongly indicate that 1) date-palm fruit is a potent allergen 2) sera from fruit-allergic as well as pollen-allergic patients recognize common fruit-specific epitopes 3) there is heterogeneity in patient responses to the different extracts.