狼疮性肾炎足细胞的天然免疫调节作用研究

Lupus nephritis (LN) is characterized by the deposit of immune complex and the infiltration of inflammatory cells in kidney. However its pathogenesis remains unclear. We found that the podocytes in LN expressed DC-SIGN, an innate immune molecule predominantly expressed on dendritic cells (DCs). Furthermore, DC-SIGN on podocytes in LN also functioned as a professional antigen presenting cell. Therefore we speculate that, dependent on its property of carbohydrate recognition, DC-SIGN may interact with GlcNAc in IgG, the main antibody in LN immune complex, and play a critical role in the injury of podocytes and glomeruli in LN. The present study plans to observe the cell adhesion, induction of T cell proliferation and differentiation, signaling pathway including LSP-1, Raf-1, PI3K, ERK and NF-κB of DC-SIGN expressed on podocytes in LN. Then frontal affinity chromatograpthy and Western Blot will be used to detect the combination between DC-SIGN and GlcNAc in IgG in LN. Therefore the regulation of podocytes and its DC-SIGN in LN immune response and glomerular injury will be systematically explored. We hope that it will provide new theoretical evidence for the relation between podocyte immune regulation and glomerular injury in LN, and search for a new interference pathway for clinical treatment and prevention.

狼疮性肾炎（LN）主要以肾脏免疫复合物沉积及炎症细胞浸润为主要特点，其发病机制尚不清楚。我们发现，LN足细胞可表达属树突状细胞（DC）标志的天然免疫分子DC-SIGN，并具备专职抗原递呈细胞功能，推测可能依赖其糖识别特性与LN免疫复合物主要抗体IgG所含糖基化修饰GlcNAc结合，在LN足细胞及肾小球损伤中发挥关键作用。本研究拟结合体内外实验，观察LN足细胞DC-SIGN细胞黏附，刺激T细胞增殖与分化，及LSP-1、Raf-1、PI3K、ERK、NF-κB等相关信号通路。进一步采用前沿亲和色谱法及Western Blot法检测足细胞DC-SIGN与LN免疫复合物中IgG及其所含GlcNAc结合识别。系统探讨足细胞及其DC-SIGN调控在LN免疫应答及肾小球损伤中的作用机制。籍此，以DC-SIGN为靶点，为阐明足细胞免疫调控与LN肾小球损伤关系提供新的理论依据，为临床防治寻找新的干预途径。

足细胞是免疫复合物的主要攻击对象，其可作为免疫细胞积极参与肾小球损伤的发生发展。DC-SIGN系天然免疫分子，具有免疫识别、介导细胞黏附及正负免疫调控功能。本研究探讨狼疮性肾炎（LN）中足细胞的DC-SIGN表达及其在LN中的作用。我们发现，LN患者肾小球可见DC-SIGN及IgG1表达。DC-SIGN能与足细胞标志性蛋白nephrin共表达。LN小鼠自20周龄起伴随尿蛋白增加，肾小球亦见DC-SIGN及IgG1表达，至24周龄出现肾功能恶化；经针对DC-SIGN抗体干预后，尿蛋白减少，肾功能缓解。经LN鼠血清刺激后，小鼠足细胞DC-SIGN、MHC II、CD80表达上调，体外刺激T细胞增殖能力增强，且T细胞分泌后的IFN-γ/IL-4比值增高；经抗DC-SIGN抗体干预，足细胞DC-SIGN、MHC II、CD80表达均下调，且刺激T细胞增殖能力减弱，IFN-γ/IL-4比值下降。利用LN小鼠血清刺激发现，小鼠足细胞中Raf-1 S338、pERK以及核转录因子（NF-κB）明显上调，而LSP-1下调。利用免疫共沉淀发现，LN足细胞DC-SIGN 可与IgG1上GlcNAc相互作用，并影响DC-SIGN刺激T细胞以及诱导T细胞活化。上述结果表明，LN足细胞可表达具有重要免疫调控作用的天然免疫分子DC-SIGN，其表达活化Raf-1 S338、pERK以及NF-κB，而对LSP1有抑制作用。LN足细胞DC-SIGN通过与免疫复合物中IgG1上GlcNAc相互作用，介导足细胞发挥刺激T细胞增殖、诱导T细胞向Th1细胞分化等DC样细胞功能，从而参与LN局部组织炎症免疫反应；而抑制DC-SIGN可调抑足细胞免疫功能，并产生防治效应。