Mechanisms of IgM mediated activation of the complement system

总结 免疫球蛋白（IgM）是一种进化中的古老抗体，是第一种抗体， 是由感染引起的几种IgM以天然抗体的形式存在， 在发育的早期阶段获得免疫力。与任何其他类型的抗体不同， 拷贝足以激活经典补体系统，并且几种单克隆IgM 在癌症治疗上显示出巨大的潜力。尺寸大，高度 糖基化和IgM的结构异质性使它们难以进行结构修饰。 研究和迄今为止的分子机制，抗原结合如何激活IgM，以启动 补体级联反应仍然不清楚。相比之下，详细了解结构和 免疫球蛋白g（IgG）的各种相互作用对于它们的发展至关重要， 生物治疗的首要分子平台。因此，类似的理解水平 IgM的合成将是其发展为一类新的生物治疗药物的关键。 这项建议旨在应用结构质谱技术，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 控制补体级联激活的免疫球蛋白M内。各种类型的IgM抗原 将使用氢/氘交换和X射线足制备和分析复合物 用质谱打印以追踪结合后IgM内的局部结构变化 抗原的不同呈递（Aim 1）。电子显微镜和小角X射线散射 将用于观察和跟踪抗原-IgM复合物中的大规模结构转变 (Aim 2）。这些技术的完整组合将用于研究IgM如何招募和激活 补体级联反应的初始组分C1（目的3）。的分子机制 IgM如何识别抗原和募集补体将为调节免疫调节提供基础。 免疫系统生物治疗新范例。

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.