Kemp E H, Waterman E A, Ajjan R A, Smith K A, Watson P F, Ludgate M E, Weetman A P
Division of Clinical Sciences, Northern General Hospital, University of Sheffield, Sheffield, UK.
Clin Exp Immunol. 2001 Jun;124(3):377-85. doi: 10.1046/j.1365-2249.2001.01554.x.
The sodium-iodide symporter (NIS) is a novel autoantigen in autoimmune thyroid disease. In the present study we have characterized the antigenic domains on the human symporter which are recognized by autoantibodies from patients with either Graves' disease (GD) or autoimmune hypothyroidism (AH). Deletion derivatives of complementary DNA (cDNA) encoding the Na(+)/I(-) symporter were constructed using polymerase chain reaction (PCR) amplification. These deletion constructs were translated in vitro with the concomitant incorporation of [(35)S]methionine into the protein products. The reactivity of seven GD and six AH sera, which were known to contain symporter-binding antibodies, to each of the radiolabelled modified symporters was then determined in immunoprecipitation experiments. Analyses of the results obtained in the radiobinding assays suggest the existence of multiple antibody binding sites on human NIS (hNIS), including regions between amino acids (aa) 1--134, 191--286, 290--411, 411--520 and 520--588. Computer prediction of the potential B cell epitopes on the symporter revealed that, apart from aa 134--191, all the epitope domains identified overlapped, at least in part, with areas predicted to be highly antigenic. Interestingly, the antigenic domains represented by aa 191--286, 290--411 and 411--520 include regions of the polypeptide which form putative extracellular domains in the secondary structure model of the rat symporter. No correlation between the recognition of specific epitopes on the human symporter and the type of autoimmune thyroid disease was demonstrated.
钠-碘同向转运体（NIS）是自身免疫性甲状腺疾病中的一种新型自身抗原。在本研究中，我们对人类同向转运体上被格雷夫斯病（GD）或自身免疫性甲状腺功能减退症（AH）患者的自身抗体识别的抗原结构域进行了表征。使用聚合酶链反应（PCR）扩增构建编码Na(+)/I(-)同向转运体的互补DNA（cDNA）缺失衍生物。这些缺失构建体在体外进行翻译，同时将[(35)S]甲硫氨酸掺入蛋白质产物中。然后在免疫沉淀实验中测定已知含有同向转运体结合抗体的7份GD血清和6份AH血清对每种放射性标记的修饰同向转运体的反应性。对放射结合试验结果的分析表明，人类NIS（hNIS）上存在多个抗体结合位点，包括氨基酸（aa）1--134、191--286、290--411、411--520和520--588之间的区域。对同向转运体上潜在B细胞表位的计算机预测显示，除了aa 134--191外，所有鉴定出的表位结构域至少部分与预测为高度抗原性的区域重叠。有趣的是，由aa 191--286、290--411和411--520代表的抗原结构域包括在大鼠同向转运体二级结构模型中形成假定细胞外结构域的多肽区域。未证明人类同向转运体上特定表位的识别与自身免疫性甲状腺疾病类型之间存在相关性。
