B-1细胞是与自身免疫反应密切相关的B淋巴细胞亚群。与B-2细胞不同，B-1来源于胎肝，成体内B-1细胞数量平衡依赖于其自身增殖和活力的维持，但目前其这一特性的调节机制并不清楚。我们发现，与正常人相比，类风湿关节炎(RA)患者外周血B-1细胞比例明显上调，进一步的研究提示这与其Flt3/CD135分子表达水平升高相关；另外我们发现，做为Flt3/CD135的直接调控分子，miR-150的水平在RA患者B-1细胞内显著下降，且在B-1细胞内二者表达水平呈负相关。因此我们推测：在RA患者B-1细胞中，miR-150水平的异常降低导致Flt3/CD135表达水平升高，这导致细胞增殖及活力调控失衡和B-1细胞异常增多，进而参与了RA发生发展的过程。本课题的完成将阐明RA中miR-150/Flt3调控通路参与B-1细胞增殖及活力异常调节的作用机制，并为RA的防治提供潜在的药物靶点。

B-1 cells are a sub-class of B lymphocytes that are involved in the autoimmune response. B-1 cells arise from precursors in the fetal liver, which is different from B-2 cells. The maintenance of B-1 cells in adult depends on its own proliferation and varibility. However, the regulation mechanisms about the proliferation and varibility of B-1 cells are still unclear. In our study, we found that the proportion of B-1 cells was significantly increased in peripheral blood of patients with rheumatoid arthritis (RA) compared to normal controls. Further results showed that the overexpression of Flt3/CD135 promoted the expansion of B-1 cells. We also found that miR-150, which is a direct regulator of Flt3/CD135, was significantly decreased in B-1 cells of patients with RA compared to normal controls. Moreover, the expression level of miR-150 was negatively correlated with Flt3/CD135 in B-1 cells. Thus, we hypothesize that abnormal decrease of miR-150 leads to the overexpression of Flt3/CD135 and thereby promotes the proliferation and varibility of B-1 cells in RA. And then the expansion of B-1 cells promotes the development of RA. This study will clarify the mechanism of miR-150/Flt3 induced abnormality of B-1 cells in RA and provide potential drug targets for the treatment of RA.

结题摘要 本课题利用CD20+CD27+CD43+CD70-作为标志，检测了类风湿关节炎（RA）患者外周血B-1细胞数量。结果显示，RA中B-1细胞数量减少，与健康对照及骨关节炎（OA）患者相比，差异具有显著性。对患者临床特征分析进一步提示，RA中B-1细胞数量与患者血清IgM水平、患者病程以及IgM型类风湿因子（RF）水平呈正相关。RA患者B1细胞数还与B10以及switched memory这两种B细胞亚群正相关，与CD3+及CD8阳性T细胞数量也呈正相关。而与CCP抗体水平，RA患者疾病活动度（用DAS28表示）以及患者年龄不相关。 为进一步探讨RA中B-1细胞功能异常及其在RA中的作用，本课题采用LPS刺激活化B-1细胞，活化的B-1细胞分泌IgM的水平用ELISPOT检测。结果显示，与健康对照相比，RA患者中B-1细胞活化后，分泌IgM的能力降低。但ELISA法检测RA患者血清中的天然IgM（natural IgM，nIgM）水平与健康对照相比无显著性差异。 因此本项目的初步结论是，RA患者外周血B-1细胞数量及活化后分泌IgM的能力均降低。但并未显著影响血清中nIgM的水平。进一步的机制研究将探讨在RA炎症因子作用下，外周血B1细胞在RA中致病的机制，包括抗原提呈、刺激效应T细胞增殖分化以及与其他B细胞亚类之间的相互作用等。