Identification and characterization of the major allergens of buckwheat

Background: Buckwheat (BW) has been recognized as a common food allergen in Korea, Japan, and other countries. Until now, serologic findings of BW foo d-allergic patients and its major allergenic components have not been clari fied. In this study, we analyzed the serologic findings of BW food allergy and characterized its major allergenic components. Methods: Nineteen BW-allergic subjects with symptoms after BW ingestion and 15 asymptomatic control subjects with positive skin prick test to BW were recruited. BW-specific IgE was measured with the Pharmacia CAP kit. Allerge nic components of BW were analyzed by IgE immunoblotting, periodate oxidati on, two-dimensonal PACE, and sequencing of N-terminal amino acids. Results: From the BW-allergic patients and asymptomatic controls, the sensi tivity (100%), specificity (53%), and negative (100%) and positive predicti ve values (73%) of Pharmacia CAP specific IgE for diagnosis were estimated. The prevalence of IgE binding to 24-kDa (pI 8.3), 16-kDa (pI 5.6), and 9-k Da (pI 5.0/ 6.0) allergens was higher than 50% in BW-allergic and asymptoma tic subjects. However, the specific IgE to split 19-kDa (pI 6.5/7.0) allerg ens were more specifically found in BW-allergic patients than in asymptomat ic subjects (78% vs 7%). N-terminal amino-acid sequences of 19-kDa and 16-k Da allergens showed moderate and weak homology to the 19-kDa globulin prote in of rice and alpha -amylase/trypsin inhibitor of millet, respectively. Th e N-terminus of the 9-kDa isoallergens were not different from each other a nd were identified as the reported trypsin inhibitors of BW. Attenuation of the IgE binding to the 9-kDa allergen was found with periodate oxidation. Conclusions: The allergens of 24, 19, 16, and 9 kDa are strong candidates t o be major allergens, and the 19-kDa allergen was relatively specific for B W-allergic patients. Moreover, measurement of BW-specific IgE and the featu res of immunoblotting should be very useful tools in the diagnosis of BW al lergy.