Carbohydrate residues downstream of the terminal Galα(1,3) Gal epitope modulate the specificity of xenoreactive antibodies
Carbohydrate residues downstream of the terminal Galα(1,3) Gal epitope modulate the specificity of xenoreactive antibodies
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DOI：
10.1038/sj.icb.7100111
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发表时间：
2007-11-01
影响因子：
4
通讯作者：
Sandrin, Mauro S.
中科院分区：
文献类型：
--
作者：
Milland, Julie;Yuriev, Elizabeth;Sandrin, Mauro S.
碳水化合物参与许多免疫反应，包括排斥不相容的血液，组织和器官。具有Gal α（1，3）Gal表位的碳水化合物抗原被人体中的天然抗体识别，并对猪到人异种移植构成主要障碍。转基因猪已被证实不具有功能性α 1，3半乳糖基转移酶（α 1，3 GT），该酶可将α Gal转移至N-乙酰乳糖胺（LacNAc）型寡糖。然而，低水平的Gala（1，3）Gal在α 1，3GT敲除动物中仍以脂质异三己糖神经酰胺（iGb 3）的形式表达，其由iGb 3合酶在乳糖（Lac）型核心结构上产生。在这里，我们定义了一系列的单克隆抗体（mAb）的反应性产生的α 1，3GT-/-小鼠免疫兔红细胞（RbRBC），作为一个丰富的来源的脂质连接的抗原。有趣的是，一种mAb（15.101）与LacNAc上的合成和细胞表面表达的Gal α（1，3）Gal弱结合，但与Lac核心上的抗原形式（包括iGb 3）强结合。三维模型表明末端α-连接的Gal紧密结合到抗体结合腔中。此外，预测了抗体与第二和第三单糖单元的相互作用。总的来说，我们的研究结果表明，虽然末端碳水化合物残基赋予大部分的结合亲和力，精细的特异性是由随后的残基中的寡糖。
Carbohydrates are involved in many immunological responses including the rejection of incompatible blood, tissues and organs. Carbohydrate antigens with Gal alpha(1,3)Gal epitopes are recognized by natural antibodies in humans and pose a major barrier for pig-to-human xenotransplantation. Genetically modified pigs have been established that have no functional alpha 1,3galactosyltransferase (alpha 1,3GT), which transfers alpha Gal to N-acetyllactosamine ( LacNAc) type oligosaccharides. However, a low level of Gala( 1,3) Gal is still expressed in a1,3GT knockout animals in the form of a lipid, isoglobotrihexosylceramide (iGb3), which is produced by iGb3 synthase on lactose ( Lac) type core structures. Here, we define the reactivity of a series of monoclonal antibodies (mAb) generated in alpha 1,3GT-/- mice immunized with rabbit red blood cells (RbRBC), as a rich source of lipid-linked antigens. Interestingly, one mAb (15.101) binds weakly to synthetic and cell surface-expressed Gal alpha(1,3)Gal on LacNAc, but strongly to versions of the antigen on Lac cores, including iGb3. Three-dimensional models suggest that the terminal alpha-linked Gal binds tightly into the antibody-binding cavity. Furthermore, antibody interactions were predicted with the second and third monosaccharide units. Collectively, our findings suggest that although the terminal carbohydrate residues confer most of the binding affinity, the fine specificity is determined by subsequent residues in the oligosaccharide.