Cram D S, Fisicaro N, Coppel R L, Whittingham S, Harrison L C
Burnet Clinical Research Unit, Walter and Eliza Hall Institute of Medical Research, Australia.
J Immunol. 1990 Jul 15;145(2):630-5.
High titer IgG autoantibodies to the 70-kDa polypeptide component (p70) of the U1 ribonucleoprotein (RNP) complex occur in the sera of patients with mixed connective tissue disease, SLE, and related rheumatic diseases. To gain insight into the pathogenesis and diversity of this antibody response we have used recombinant DNA technology to map the linear B cell epitopes on p70. A full length 1.7-kb cDNA clone encoding p70 was isolated from a human placental library and restriction fragments or polymerase chain reaction-generated fragments of the gene subcloned into the bacterial expression vector pGEX. Purified fusion proteins representing specific regions of p70 were immunoblotted with a panel of 70 anti-(U1)RNP+ sera containing anti-p70 antibodies. Six epitopes, four major (A, B, C, and F) and two minor (D and E) were mapped and were located throughout the molecule. The anti-(U1)RNP sera displayed heterogeneity in their pattern of reactivity to the six epitopes although reactivity to epitope C was more frequently associated with SLE rather than mixed connective tissue disease. The identification of multiple B cell epitopes on p70 is consistent with the concept that this self Ag drives the autoantibody response.
针对U1核糖核蛋白（RNP）复合物70-kDa多肽成分（p70）的高滴度IgG自身抗体存在于混合性结缔组织病、系统性红斑狼疮及相关风湿性疾病患者的血清中。为深入了解这种抗体反应的发病机制和多样性，我们利用重组DNA技术绘制了p70上的线性B细胞表位图谱。从人胎盘文库中分离出一个编码p70的全长1.7-kb cDNA克隆，并将该基因的限制性片段或聚合酶链反应产生的片段亚克隆到细菌表达载体pGEX中。用一组含有抗p70抗体的70份抗（U1）RNP +血清对代表p70特定区域的纯化融合蛋白进行免疫印迹分析。确定了六个表位，四个主要表位（A、B、C和F）和两个次要表位（D和E），它们分布于整个分子。抗（U1）RNP血清对这六个表位的反应模式存在异质性，尽管对表位C的反应更常与系统性红斑狼疮而非混合性结缔组织病相关。p70上多个B细胞表位的确定与这种自身抗原驱动自身抗体反应的概念一致。
