High-Affinity IgE Recognition of a Conformational Epitope of the Major Respiratory Allergen Phl p 2 As Revealed by X-Ray Crystallography
High-Affinity IgE Recognition of a Conformational Epitope of the Major Respiratory Allergen Phl p 2 As Revealed by X-Ray Crystallography
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DOI：
10.4049/jimmunol.0803018
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发表时间：
2009-02-15
影响因子：
4.4
通讯作者：
Markovic-Housley, Zora
中科院分区：
文献类型：
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作者：
Padavattan, Sivaraman;Flicker, Sabine;Markovic-Housley, Zora
我们报告的三维结构之间的主要呼吸道草花粉过敏原Phl p 2和其特定的人IgE衍生的Fab的复合物。Phl p 2特异性人IgE Fab已从花粉过敏患者的淋巴细胞构建的组合文库中分离。当将IgE Fab的可变结构域移植到人IgG 1上时，产生的Ab（huMab 2）强烈抑制过敏患者的IgE与Phl p 2的结合以及过敏原诱导的嗜碱性粒细胞脱颗粒。通过表面等离子体共振分析过敏原与Ab的结合产生了非常低的解离常数（K-D = 1.1 × 10（-10）M），这与IgE和Fc β RI之间的解离常数相似。Phl p 2/IgE Fab复合物的结构通过X射线晶体学测定至1.9埃分辨率，揭示了由Phl p 2的四链反平行β折叠的平面表面组成的构象表位（876埃（2））。IgE定义的优势表位是不连续的，由21个残基形成，主要位于β链内。在21个残基中，9个主要通过氢键和货车范德华相互作用与IgE Fab的6个CDR中的5个（L1、L3、H1、H2、H3）直接相互作用。我们的研究结果表明，IgE抗体识别构象表位具有高亲和力，并提供了一个高效的效应细胞激活过敏原/IgE免疫复合物的结构基础。免疫学杂志，2009，182：2141-2151.
We report the three-dimensional structure of the complex between the major respiratory grass pollen allergen Phl p 2 and its specific human IgE-derived Fab. The Phl p 2-specific human IgE Fab has been isolated from a combinatorial library constructed from lymphocytes of a pollen allergic patient. When the variable domains of the IgE Fab were grafted onto human IgG1, the resulting Ab (huMab2) inhibited strongly the binding of allergic patients' IgE to Phl p 2 as well as allergen-induced basophil degranulation. Analysis of the binding of the allergen to the Ab by surface plasmon resonance yielded a very low dissociation constant (K-D = 1.1 x 10(-10) M), which is similar to that between IgE and Fc epsilon RI. The structure of the Phl p 2/IgE Fab complex was determined by x-ray crystallography to 1.9 angstrom resolution revealing a conformational epitope (876 angstrom(2)) comprised of the planar surface of the four-stranded anti-parallel beta-sheet of Phl p 2. The IgE-defined dominant epitope is discontinuous and formed by 21 residues located mostly within the beta strands. Of the 21 residues, 9 interact directly with 5 of the 6 CDRs (L1, L3, H1, H2, H3) of the IgE Fab predominantly by hydrogen bonding and van der Waals interactions. Our results indicate that IgE Abs recognize conformational epitopes with high affinity and provide a structural basis for the highly efficient effector cell activation by allergen/IgE immune complexes. The Journal of Immunology, 2009, 182: 2141-2151.