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

为阐明系统性红斑狼疮(SLE)发病早期产生自身抗体的自身抗原，分别采集了10只NZB/NZW F1和10只MRL/LPR小鼠血清。以小鼠胸腺瘤细胞(EL-4)裂解物为底物的免疫印迹试验表明，所有小鼠均能产生抗150 kDa自身抗体。110 kDa、75 kDa或55 kDa分子，最早4周。抗DNA抗体几乎在同一时间或在针对这四个分子的抗体之后出现。随着年龄的增长，免疫印迹中与自身抗体反应的抗原数量逐渐增加。8周龄后产生抗组蛋白抗体。在四种抗原中，110 kDa的分子被鉴定为核仁蛋白，它是一种含量丰富的核仁磷蛋白。核仁能结合DNA、RNA和核酸结合蛋白，如组蛋白H1。核仁素是细胞毒性T细胞颗粒酶A的靶标，在SLE患者和各种病毒感染患者的血清中都发现了针对核仁素的自身抗体。这些结果表明，在SLE小鼠模型中，核仁素是打破自身耐受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.