Identification of novel autoantigens using human IgG in SCID mice implanted with lacrimal and salivary grands from patients with Sjogren's Syndrome

干燥综合征(SS)是一种以慢性淋巴细胞浸润性外分泌腺为特征的慢性自身免疫性疾病，是世界范围内女性发病率较高的疾病。唾液腺和泪腺是淋巴细胞渗入的主要目标，因此导致这些腺体的组织破坏和功能降低。但SS的病因和淋巴细胞浸润机制尚不清楚。本研究的目的是寻找与SS发病和进展相关的自身抗原，为SS的临床诊断提供有用的血清学标志物。我们证明，将SS患者新鲜唾液和泪腺活检组织植入SCID小鼠皮下，可使接种腺体活检组织的20%小鼠的血清中产生高水平的人免疫球蛋白G(44-3,426μg/ml)。为了筛选新的自身抗原作为血清学标记物，我们用人唾液腺上皮细胞系(HSG和HSY)和正常人颌下腺组织文库，对SCID小鼠的血清进行了基因表达克隆分析。编码SS-A/Ro和SS-B/La的克隆被认为是SS自身抗体的主要靶标，通过该分析分离到的噬菌体克隆最多。为了进一步筛选SS中的特异性自身抗原，我们用SS患者和健康人的血清进行了血清学筛选。SS患者血清中抗5种新分离自身抗原的Ig G抗体阳性率在30%~45%之间，显著高于健康人血清。这些结果表明，我们使用SCID小鼠的方法可以识别新的特异性自身抗原，作为临床诊断SS的血清学标志。

Sjogren's syndrome (SS) is a chronic autoimmune disease characterized by chronic lymphocytic infiltration of the exocrine glands and a worldwide disease with higher prevalence in woman. The salivary and lacrimal glands are the main targets of this lymphocytic infiltration, which as a consequence leads to tissue destruction and decreased function of these glands. But the etiology of SS and mechanisms of lymphocytic infiltration is unknown. The purpose of our project was the identification of specific autoantigens contributing to the disease pathogenesis and progression in SS and useful serological markers for the clinical diagnosis of SS. We demonstrated that the implant of nondisrupted pieces of fresh salivary and lacrimal glands biopsy tissue from patients with SS into the subcutis of SCID mice results in high levels of human IgG (44-3,426μg/ml) produced by gland-infiltrated B and plasma cells in the sera of 20 % mice inoculated with gland biopsy tissue. Using the sera including human IgG from these SCID mice, we demonstrated the cDNA expression cloning analysis with two human salivary gland epithelial cell lines (HSG and HSY) and normal human submandibular grand tissue cDNA libraries in order to identify novel autoantigens as serological marker. The clone encoded SS-A/Ro and SS-B/La, known as a major target of autoantibodies in SS, had the most phage clones isolated by this analysis. To further select the specific autoantigens in SS, we carried out serological screenings using the sera of patients with SS and healthy individuals. Frequencies of IgG autoantibodies against five newerly isolated autoantigens in the sera of patients with SS showed between 30 % and 45 % in significantly higher amounts than in sera from healthy individuals. These results were suggested that our approach using SCID mice may allow the identification of novel specific autoantigens as serological markers for the clinical diagnosis of SS.