A Study on the Cross-allergenicity between Buckwheat and Rice Flour Using IgE-immunoblot Inhibition and ELISA-inhibition Test

Chun, Woo Sung; Lee, Ki Sun; Hong, Chang Ho; Lee, Soo Young

Abstract

PURPOSE
Buckwheat is one of the potent allergenic foods, whereas rice is considered as the safest and hypoallergenic food in Korea. However rice can be a causative food allergen, and several report about allergic reactions to rice in Japan. And it is partially true that there is some cross-allergenicity among cereal allergens such as buckwheat, barley, wheat, rice. So, we should consider a false positive reaction to rice during allergic skin tests, especially in cereal allergic patients. We found that a part of buckwheat allergic children showed positive skin reactions to rice antigens, without any allergic reactions after rice ingestion. Therefore the positive skin test results to rice were considered as the false positive reactions due to cross-allergenicity with buckwheat allergen. To evaluate this possibility, we undertook this study.
METHODS
To evaluate the cross-allergenicity between rice and buckwheat antigens. With the buckwheat sensitive sera and crude extracts of buckwheat flour and rice flour obtained in Korea, we carried out SDS-PAGE analysis, IgE immunoblot, IgE-immouoblot inhibition test and ELISA inhibition test.
RESULTS
Buckwheat extract showed more than 13 antigenic bands and rice extract showed more than 9 bands by SDS-PAGE analysis. IgE immunoblot revealed at least 20 IgE-binding components (ranged 120-4 kDa) with buckwheat extract. IgE-binding capacity of 22 kDa buckwheat component was markedly inhibited by rice extract and 8 kDa component was inhibited slightly. Using IgE ELISA inhibition test, we confirmed buckwheat IgE-ELISA was profoundly inhibited by rice extract, and 50% inhibition was shown in 10-100 ug/ml concentration of rice extract.
CONCLUSION
Taken together, the positive reactions to rice antigen would be shown by the result of cross-allergenicity of rice with buckwheat antigen.