Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, Tokyo, Japan.
J Immunol. 2009 Dec 15;183(12):7958-65. doi: 10.4049/jimmunol.0713276.
Although many allergens bind endogenous molecules other than Abs in the human body, whether the interaction can modulate allergenicity has been unknown. Here, we investigated the effect of the interaction of recombinant major mite group 1 allergens (Der f 1 and Der p 1), which belong to the papain-like cysteine protease family, with an endogenous protease inhibitor, cystatin A, on their allergenicity. Cystatin A bound reduced forms of the allergens, in which the cysteine residue at the catalytic center of the protease activity was reduced by treatment with L-cysteine, but did not bind oxidized forms. Cystatin A partially inhibited the binding of IgE in mite-allergic volunteers' sera to the reduced forms, but unexpectedly enhanced the basophil histamine-releasing activity. A catalytic site-mutant of Der f 1 behaved in terms of histamine release, similarly to the reduced form. Molecular modeling showed that cystatin A interacts with the allergens within a narrow area. The results indicate that interaction with cystatin A reduces the limited number of IgE epitopes of the allergens but enhances their biological activity to release histamine, suggesting a new concept, that interaction between allergens and their endogenous ligands modulates the allergenicity even toward enhancement in the effector phase. On the other hand, i.p. immunization without alum of mice with cystatin A-treated reduced Der f 1 induced less serum Der f 1-specific IgE than immunization with reduced Der f 1 alone, suggesting that endogenous protease inhibitors suppress the induction of allergen-specific IgE, which is dependent on the enzymatic activity of cysteine protease-allergens, in the sensitization process.
尽管许多过敏原除了在人体内结合 Abs 外还与其他内源性分子相互作用，但这种相互作用是否能调节过敏原性尚不清楚。在这里，我们研究了属于木瓜蛋白酶样半胱氨酸蛋白酶家族的重组主要螨组 1 过敏原（Der f 1 和 Der p 1）与内源性蛋白酶抑制剂半胱氨酸蛋白酶抑制剂 A 之间相互作用对其变应原性的影响。半胱氨酸蛋白酶抑制剂 A 结合还原形式的过敏原，其中在半胱氨酸残基的催化中心的蛋白酶活性通过用 L-半胱氨酸处理而被还原，但不结合氧化形式。半胱氨酸蛋白酶抑制剂 A 部分抑制了螨过敏志愿者血清中 IgE 与还原形式的结合，但出人意料地增强了嗜碱性粒细胞组胺释放活性。Der f 1 的催化部位突变体在组胺释放方面的行为类似于还原形式。分子建模表明，半胱氨酸蛋白酶抑制剂 A 与过敏原在一个狭窄的区域内相互作用。结果表明，与半胱氨酸蛋白酶抑制剂 A 的相互作用减少了过敏原有限数量的 IgE 表位，但增强了它们释放组胺的生物学活性，这表明了一个新概念，即过敏原与其内源性配体之间的相互作用甚至在效应阶段增强了过敏原性。另一方面，用半胱氨酸蛋白酶抑制剂 A 处理过的还原型 Der f 1 腹腔免疫没有 alum 的小鼠比单独用还原型 Der f 1 免疫产生的血清 Der f 1 特异性 IgE 少，这表明内源性蛋白酶抑制剂抑制了变应原特异性 IgE 的诱导，这依赖于半胱氨酸蛋白酶过敏原的酶活性，在致敏过程中。
