Centre for Plant Biotechnology and Genomics U.P.M. - I.N.I.A., Campus de Montegancedo Pozuelo de Alarcón, Madrid, Spain.
Allergy Service, Hospital Infanta Leonor Madrid, Spain.
Food Sci Nutr. 2014 May;2(3):260-71. doi: 10.1002/fsn3.99. Epub 2014 Mar 19.
The physical, biochemical, and immunological characteristics of plant allergens have been widely studied, but no definite conclusion has been reached about what actually makes a protein an allergen. In this sense, N-glycosylation is an exclusive characteristic of plant allergens not present in mammals and it could be implied in allergenic sensitization. With this aim, we evaluated and compared the allergenic activity of the protein fraction and the N-glycan fraction of the thaumatin-like protein and the main kiwi allergen, Act d 2. The natural allergen, Act d 2, was deglycosylated by trifluoromethanesulfonic acid treatment; the N-glycan fraction was obtained by extended treatment with proteinase K. N-glycan- and protein- fractions were recognized by specific IgE of kiwi-allergic patients. By contrast, the sugar moiety showed a reduced capacity to activate basophils and T cells, but not dendritic cells derived from patients' monocytes. Related to this, the production of cytokines such as IL6 and IL10 was increased by the incubation of dendritic cells with sugar moiety. Thus, the sugar moiety plays a significant role in sensitization, inducing the activation of antigen-presenting cells, but it is the protein fraction that is responsible for the allergic reactions.
植物过敏原的物理、生化和免疫学特性已得到广泛研究，但尚未确定是什么使蛋白质成为过敏原。从这个意义上说，N-糖基化是植物过敏原所特有的，而哺乳动物中并不存在，它可能与致敏有关。为此，我们评估并比较了甜味蛋白和主要猕猴桃过敏原 Act d 2 的蛋白部分和 N-聚糖部分的变应原活性。天然过敏原 Act d 2 通过三氟甲磺酸处理进行去糖基化；N-聚糖部分通过与蛋白酶 K 进行扩展处理获得。N-聚糖和蛋白部分被猕猴桃过敏患者的特异性 IgE 识别。相比之下，糖基部分激活嗜碱性粒细胞和 T 细胞的能力降低，但来自患者单核细胞的树突状细胞没有被激活。与此相关，与糖基部分孵育可增加树突状细胞产生细胞因子（如 IL6 和 IL10）。因此，糖基部分在致敏中起重要作用，可诱导抗原呈递细胞的激活，但引起过敏反应的是蛋白部分。
