Mechanisms of IgM mediated activation of the complement system

摘要 免疫球蛋白 µ (IgM) 是一种进化古老的抗体，是第一种抗体 为应对感染而产生。多种 IgM 作为天然抗体存在，并且至关重要 在发育的早期阶段获得免疫力。与任何其他类别的抗体不同，单一 拷贝足以激活经典补体系统，并且一些单克隆 IgM 已显示出治疗癌症的巨大潜力。尺寸大、度高 IgM 的糖基化和结构异质性使它们难以适应结构 研究并确定了抗原结合如何激活 IgM 以启动免疫反应的分子机制 补体级联反应仍不清楚。相比之下，对结构和结构的详细了解 免疫球蛋白 g (IgG) 的各种相互作用对其进步至关重要 生物治疗的首要分子平台。因此，具有相似的理解水平 IgM 的检测对于其作为新型生物治疗药物的开发至关重要。 该提案旨在应用结构质谱技术、电子显微镜 使用互补的结构方法和生物物理工具来研究结构变化 IgM 内控制补体级联的激活。各种类型的 IgM 抗原 将使用氢/氘交换和 X 射线足来制备和分析配合物 质谱打印以追踪结合后 IgM 内的局部结构变化 抗原的不同表现形式（目标 1）。电子显微镜和小角 X 射线散射 将用于可视化和跟踪抗原-IgM 复合物中的大规模结构转变 （目标 2）。技术的完整组合将用于研究 IgM 如何招募和激活 补体级联的初始成分 C1（目标 3）。的分子机制 IgM 如何识别抗原并招募补体将为调节 免疫系统为生物治疗的新范例。

SUMMARY Immunglobulin µ (IgM) is an evolutionary old class of antibody that is the first antibody produced in response to an infection. Several IgMs are present as natural antibodies and are vital for immunity during the early stages of development. Unlike any other class of antibody, a single copy is sufficient for activating the classical complement system, and several monoclonal IgMs have shown massive potential for the treatment of cancers. The large size, high degree of glycosylation, and structural heterogeneity of IgM has rendered them refractory to structural studies and to date the molecular mechanisms of how antigen binding activates IgM to initiate the complement cascade remain murky. In contrast, a detailed understanding of the structure and various interactions of immunoglobulin g (IgG) have been fundamental to their advancement as the premier molecular platform for biotherapeutics. Accordingly, a similar level of understanding of IgM will be critical for their development as a new class of biotherapeutics. This proposal aims to apply structural mass spectrometry techniques, electron microscopy with complementary structural approaches, and biophysical tools to study the structural changes within IgM that govern activation of the complement cascade. Various types of IgM-antigen complexes will be prepared and analyzed using hydrogen/deuterium exchange and X-ray foot printing with mass spectrometry to track the local structural changes within IgM upon binding different presentations of antigen (Aim 1). Electron microscopy and small angle X-ray scattering will be used to visualize and track large-scale structural transitions in the antigen-IgM complexes (Aim 2). The full combination of techniques will be used to study how IgM recruits and activates the initial component, C1, of the complement cascade (Aim 3). The molecular mechanisms of how IgM recognizes antigen and recruits complement will provide a foundation for modulating the immune system for a new paradigm in biotherapeutics.