IMMEDIATE HYPERSENSITIVE REACTIONS TO BUCKWHEAT INGESTION AND CROSS ALLERGENICITY BETWEEN BUCKWHEAT AND RICE ANTIGENS IN SUBJECTS WITH HIGH-LEVELS OF IGE ANTIBODIES TO BUCKWHEAT

Background: Immediate hypersensitive reactions induced by buckwheat in gestion are considered to be IgE-mediated. Some subjects, however, dev elop no immediate adverse reactions after buckwheat ingestion despite high levels of buckwheat-specific antigens IgE, The mechanism is unkno wn. Objective: To investigate the mechanisms. Methods: RAST for buckwh eat and rice and RAST inhibition between these antigens were performed using sera from 23 buckwheat-sensitive subjects and 30 buckwheat-tole rant subjects who had IgE antibodies for both buckwheat and rice. Resu lts: RAST values for buckwheat and rice were significantly correlated with each other (P < .01) in the buckwheat-tolerant group, but not in the buckwheat-sensitive group, This suggests the IgE antibodies from t he subjects without any overt symptoms after buckwheat ingestion recog nize the cross-reactive epitope between buckwheat and rice, whereas th e IgE antibodies from those with immediate reactions to buckwheat inge stion do not. RAST inhibition assays were performed to evaluate this, RAST inhibition of heterogeneous combination of inhibitor and disc ant igen such as rice and buckwheat was significantly smaller than that of homologous combination of rice and rice or buckwheat and buckwheat in the group with immediate symptoms after buckwheat ingestion. There wa s no significant difference in RAST inhibition between homologous and heterogeneous combinations in the group without the symptoms. Conclusi ons: There was cross-reactivity with IgE antibodies between buckwheat and rice and IgE antibodies from the buckwheat-tolerant subjects with high levels of IgE antibodies from the buckwheat might recognize the e pitopes on buckwheat antigens which cross-react with rice antigens, wh ereas IgE antibodies from the buckwheat-sensitive subjects might bind to buckwheat-specific epitopes.