The role of IgG subclass in the pathogenesis of bullous pemphigoid

本文从以下几个方面探讨了大疱性类天疱疮(BP)发病机制中免疫球蛋白G亚类的作用：(1)大疱性类天疱疮免疫球蛋白亚类是否与BP抗原的不同结合部位结合；(2)哪个BP-Ig G亚类直接导致真皮-表皮分离。(3)BP抗原结合的BP-Ig G亚类是否向细胞内传递信号。(4)BP-IgG1激活的补体是否能诱导细胞溶解。(5)体外培养的角质形成细胞与BP抗原结合后，角质形成细胞是否分泌任何化学物质(不包括蛋白水解酶)。首先，采用阻断免疫荧光法、免疫印迹法和ELISA法检测BP抗原上BP抗体亚类的结合部位。结果表明，BP-IgG1、IgG2和IgG4均可与BP抗原的同一表位结合，但不同患者之间有较大的差异。其次，我们用激光共聚焦扫描显微镜观察了荧光黄负载角质形成细胞的垂直切片。垂直图像显示BP-Ig G与正常Ig G之间无明显差异。3.利用激光共聚焦扫描显微镜观察了分别反映细胞内钙离子浓度([Ca^&lt；2&gt；i)、细胞内pH和膜电位的Fluo-3/Am、snarf-1/Am和Dioc-5荧光强度变化的时程。结果表明，BP-IgG1可诱导角质形成细胞在脱钙条件下一过性升高[Ca~(2+)]_2~[gt；]i。膜电位无明显变化。4.加入补体后，BP-IgG1引起细胞内[Ca~(2+)]i一过性升高。但同时未观察到负载荧光黄的角质形成细胞有细胞溶解现象。第五，我们检测了各种皮肤病的皮损中是否存在尿激酶受体(UKR)。结果表明，UKR存在于寻常型天疱疮的细胞间隙中，而在BP的基底膜上未见。

We examined the role of IgG subclass in the mechanism of bullous pemphigoid (BP) as follows : (1)Whether BP IgG subclass binds to the different binding site of BP antigen or not. (2)Which BP IgG subclass induces directly dermo-epidermal separation. (3)Whether BP IgG subclass bound to BP antigen passes some signal into the cell or not. (4)Whether complement activated by BP IgG1 induces cell lysis or not. (5)Whether cultured keratinocytes secrete any chemical substance (ex.protease) or not, after BP IgG subclass binds to BP antigen on the surface of cultured keratinocytes.First, we examined the binding site of BP IgG subclass on BP antigen, using blocking immunofluorescense, immunoblot and ELISA.The result suggested that BP IgG1, IgG2 and IgG4 could bind to the same epitope of BP antigen, but considerable variation occured between patients. Second, we observed vertical section of luciffer yellow loaded keratinocytes, by using confocal laser scanning microscopy. The vertical image showed that there was no difference between BP IgG and normal IgG.Third, using confocal laser scanning microscopy, we chased the time course of fluorescent intensity change of fluo-3/am, snarf-1/am and dioc-5 which indicated intracellular Ca^<2+> concentration ([Ca^<2+>]i), intracellular pH and membrane potential, respectively. The result showed BP IgG1 induced a transient increase of [Ca^<2+>]i, even though fluo-3 loaded keratinocytes were incubated in Ca removed medium. There was no significant change about membrane potential. Forth, BP IgG1 induced a transient increase of [Ca^<2+>]i, when complement was added. But at the same time, it wasn't observed the cytolysis of luciffer yellow loaded keratinocytes. Fifth, we examined the presence of urokinase receptor (UKR) in the lesional skin of various skin diseases. The result showed that UKR was observed in the intercellular space of pemphgus vulgaris, but not observed at the basement membrane zone of BP.