NUCLEOLIN AS THE EARLIEST TARGET MOLECULE OF AUTOANTIBODIES PRODUCED IN MRL/lpr LUPUS PRONE MICE

为了阐明在系统性红斑狼疮（SLE）疾病早期产生自身抗体的自身抗原，我们分别和顺序地收集了10只NZB/NZW F1和10只MRL/lpr小鼠的血清样本。使用小鼠胸腺瘤细胞（EL-4）裂解物作为底物的免疫印迹，发现所有小鼠都能产生针对150kDa的自身抗体。110kDa， 75kDa或55kDa分子，早在4周。抗dna抗体几乎同时或在针对这四种分子的抗体之后产生。免疫印迹中与自身抗体反应的抗原数量随着年龄的增长而逐渐增加。8周龄后产生组蛋白抗体。在这四种抗原中，110kDa分子被鉴定为核仁蛋白，这是一种丰富的核仁磷酸化蛋白。核仁蛋白结合DNA、RNA和核酸结合蛋白如组蛋白H1。核仁蛋白是细胞毒性T细胞颗粒酶a的靶标，在SLE患者以及各种病毒感染患者的血清中发现了针对核仁蛋白的自身抗体。这些结果表明，核仁蛋白是SLE小鼠模型中破坏自身耐受性和启动自身抗体扩散的免疫优势分子之一。

To elucidate the autoantigen against which autoantibodies are produced in the earliest phase of the disease process of systemic lupus erythematosus (SLE), serum samples were collected individually and serially from 10 NZB/NZW F1 and 10 MRL/lpr mice. Using immunoblots with mouse thymoma cell (EL-4) lysates as substrates, all mice were found to generate autoantibody against either 150kDa. 110kDa, 75kDa or 55kDa molecule as early as 4 weeks. Anti-DNA antibodies occurred almost at the same time or after those against these four molecules. The number of antigens reactive with autoantibodies in immunoblots increased gradually with age. Antibodies against histone molecules were produced after 8 weeks of age. Among the four antigens, the 110kDa molecule was identified as nucleolin, which is an abundant nucleolar phosphoprotein. Nucleolin binds DNA, RNA and nucleic-acid binding proteins such as histone H1. Nucleolin is a target of granzyme A of cytotoxic T cells, and autoantibodies against it are found in sera from patients with SLE as well as those with various viral infections. These results indicate that nucleolin is one of the immunodominant molecules which break down self-tolerance and initiate autoantibody-spreading in mouse model of SLE.