A novel lectin-dependent activation pathway of complement

一种新的凝集素依赖性补体激活途径

• 批准号: 06044189
• 负责人: FUJITA Teizo
• 金额: $ 1.54万
• 依托单位: Fukushima Medical College
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044189/
• 关键词: MBP; MASP; C1; Reuhmatoid arthritis; IgG

Serum mannose-binding protein(MBP)is a C-type lectin capable of activating the complement system (the lectin pathway). A serine protease designated MASP (MBP-associated serine protease) is involved in the activation by MBP,exerting C4-and C2-activating capacity when bound to MBP on its ligands.1.To clarify the mechanisms by which C1r/C1s is substitute for MASP in the activation of the lectin patheway, we measured the affinity of C1r/C1s or MASP to C1q and MBP in a Biacore apparatus. The results indicate that the affinities of the four possible mixtures are very similar. Since MBP-MASP and C1q-C1r/C1s complex were present in plasma, the other factors would influence the interaction of MBP and C1r/C1s.2.We inverstigated reconstitution of recombinant MBPs and MASP for exhibiting complement activation. Wild type rMBP was found to be able to be associated with MASP,resulting in complement activation, whereas rMBP_D in which glycine is substituted with asparatic acid in the fifth collagen re … More peat and responsible for the complement-dependent opsonic defect is unable to activate complement when incubated with MASP.These results indicate that lack of complement-activating capacity of rMBP_D might be due to inability of association with MASP.3.To evalute the role of MBP in rheumatoid arthritis, we characterized the MBP-binding substances in sera of these patients. An enzyme linked immunosorbent assay (ELISA) was performed to detect the MBP-binding substances in sera of patients with RA.Sera of patients with RA showed higher MBP binding compared with those of normal controls. To characterize the MBP-binding substances, we applied sera of two patients with RA to an immobilized MBP column. Both IgG and IgM-RF were found in the binding substances of patients with RA eluted from MBP-column, whereas IgG was found in that of normal control. The results of molecular sieve chromatography showed that the binding substances of patients with RA consisted of immune complexes containing IgG and IgM-RF.These binding substances were specifically bound to MBP,and then MBP-MASP complexes consumed C4. Therefore, MBP binds to immune complexes consisting of IgG and IgM-RF,and probably recognizes either mannose of IgM-RF or N-acethylglucosamine of agalacto IgG.The lectin pathway would be activated in sera of patients with RA. Less

血清甘露糖结合蛋白 (MBP) 是一种能够激活补体系统（凝集素途径）的 C 型凝集素，称为 MASP（MBP 相关丝氨酸蛋白酶）的丝氨酸蛋白酶参与 MBP 的激活，发挥 C4-和与配体上的MBP结合时的C2激活能力。1.阐明C1r/C1s替代MASP激活凝集素的机制我们在 Biacore 装置中测量了 C1r/C1s 或 MASP 对 C1q 和 MBP 的亲和力。结果表明，由于 MBP-MASP 和 C1q-C1r/C1s 复合物存在，因此四种可能的混合物的亲和力非常相似。血浆中，其他因素会影响MBP和C1r/C1s的相互作用。2.我们研究了重组MBP和MASP的重构野生型 rMBP 被发现能够与 MASP 相关，从而导致补体激活，而 rMBP_D（第五种胶原蛋白中的甘氨酸被天冬氨酸取代）则导致补体依赖性调理缺陷。与 MASP 一起孵育时无法激活补体。这些结果表明 rMBP_D 缺乏补体激活能力可能是由于无法与 MASP 结合所致。3.评估类风湿性关节炎中的MBP，我们对这些患者血清中的MBP结合物质进行了酶联免疫吸附测定（ELISA）来检测RA患者血清中的MBP结合物质。RA患者的血清表现出较高的MBP。为了表征 MBP 结合物质，我们将两名 RA 患者的血清应用到固定的 MBP 柱上，在结合中发现了 IgG 和 IgM-RF。分子筛层析结果显示，RA患者的结合物质开始为含有IgG和IgM-RF的免疫复合物。 MBP与MBP特异性结合，MBP-MASP复合物消耗C4，因此MBP与IgG和IgM-RF组成的免疫复合物结合，可能识别甘露糖或甘露糖。 IgM-RF或半乳糖IgG的N-乙酰氨基葡萄糖。RA患者血清中的凝集素途径会被激活。