Mechanisms of IgM mediated activation of the complement system

摘要 免疫球蛋白(IgM)是一种进化的古老抗体，是第一抗体 为应对感染而产生的。几种免疫球蛋白以天然抗体的形式存在，是至关重要的 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，单个抗体 复制足以激活经典的补体系统，以及几种单抗IgM 已经显示出治疗癌症的巨大潜力。体型大、程度高 糖基化和IgM的结构异质性使它们难以对结构 抗原结合如何激活IgM以启动免疫球蛋白的分子机制研究 补充级联仍不明朗。相比之下，对结构和结构的详细了解 免疫球蛋白g(Igg)的各种相互作用是它们发展为 首屈一指的生物治疗分子平台。因此，类似程度的理解 对于它们作为一类新的生物治疗药物的发展将是至关重要的。 这项提案旨在应用结构质谱学技术、电子显微镜 用互补的结构方法和生物物理工具来研究结构变化 在免疫球蛋白中，控制补体级联的激活。各种类型的IgM抗原 将利用氢/氚交换和X射线脚来制备和分析络合物 用质谱仪打印以跟踪结合时IgM内的局部结构变化 抗原的不同呈现形式(目标1)。电子显微镜与小角X射线散射 将被用于可视化和跟踪抗原-IgM复合体中的大规模结构转变 (目标2)。技术的全面结合将被用来研究IgM是如何招募和激活的 补体级联的初始成分c1(目标3)。其分子机制的研究进展 IgM识别抗原和招募补体的方式将为调节 免疫系统在生物治疗中的新范例。

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.