Tanaka Kazuko, Matsumoto Kenji, Akasawa Akira, Nakajima Toshiharu, Nagasu Takeshi, Iikura Yoji, Saito Hirohisa
Department of Allergy and Immunology, National Research Institute for Child Health and Development, Showa University School of Medicine, Tokyo, Japan.
Int Arch Allergy Immunol. 2002 Sep;129(1):49-56. doi: 10.1159/000065173.
Buckwheat is becoming popular in many countries as a health food and the incidence of buckwheat allergy is increasing in Asia. The ingestion of small amounts sometimes provokes an anaphylactic reaction. However, it remains controversial which is the major allergen responsible for such reactions.
The patients whose sera are positive for buckwheat-specific IgE antibody measured by the CAP system fluorescein-enzyme immunoassay (CAP-FEIA) were classified into two subgroups depending on the history of immediate hypersensitivity reactions (IHR). Major buckwheat allergens were identified with immunoblotting, ELISA and N-terminal amino acid sequencing. Various treatments such as pepsin digestion were added to characterize the proteins.
We found that the 24-kD protein that had previously been reported to be a major allergen reacted to IgE antibodies present in sera from almost all subjects (19/20) regardless of symptoms. On the other hand, 16- and 19-kD proteins were bound with IgE antibodies present in sera from 9 of the 10 patients with IHR including 8 patients with anaphylaxis but not in sera from buckwheat-specific IgE-positive subjects without IHR. After pepsin treatment, the 16-kD protein but not the 19- and 24-kD proteins remained undigested and preserved the capacity of IgE binding. This pepsin-resistant 16-kD protein had no homology with the 24-kD protein by the N-terminal amino acid sequencing.
The 16-kD buckwheat protein was resistant to pepsin digestion and appeared to be responsible for IHR including anaphylaxis, while the pepsin-sensitive 24-kD protein was responsible for CAP-FEIA but not IHR.
荞麦作为一种健康食品在许多国家越来越受欢迎，并且在亚洲荞麦过敏的发生率正在上升。摄入少量荞麦有时会引发过敏反应。然而，关于引发此类反应的主要过敏原是什么仍存在争议。
通过CAP系统荧光酶免疫测定法（CAP - FEIA）检测出荞麦特异性IgE抗体呈阳性的患者，根据速发型过敏反应（IHR）病史分为两个亚组。通过免疫印迹、酶联免疫吸附测定和N端氨基酸测序鉴定主要的荞麦过敏原。添加各种处理方法如胃蛋白酶消化来表征这些蛋白质。
我们发现，先前报道的主要过敏原24 - kD蛋白与几乎所有受试者（19/20）血清中的IgE抗体发生反应，无论有无症状。另一方面，16 - kD和19 - kD蛋白与10例IHR患者中9例患者血清中的IgE抗体结合，其中包括8例过敏反应患者，但在无IHR的荞麦特异性IgE阳性受试者血清中未发现。胃蛋白酶处理后，16 - kD蛋白未被消化，而19 - kD和24 - kD蛋白被消化，并且16 - kD蛋白保留了IgE结合能力。通过N端氨基酸测序，这种耐胃蛋白酶的16 - kD蛋白与24 - kD蛋白无同源性。
16 - kD荞麦蛋白对胃蛋白酶消化具有抗性，似乎是包括过敏反应在内的IHR的原因，而对胃蛋白酶敏感的24 - kD蛋白是CAP - FEIA阳性的原因，但不是IHR的原因。
