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

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 ingibition 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.