Force spectroscopy in immunological studies

从历史上看，免疫学研究一直以蛋白质为中心，信号事件通常被定义为多肽的生化变化。生物物理因素在这一机制中的作用大多被忽视了。在上一次NSERC拨款的资助下，我们使用基于原子力显微镜（AFM）的单细胞力光谱（SCFS）来阐明由细胞膜生物物理变化驱动的几个重要免疫事件。我们发现，固体物质与表面脂质接触强度很大，导致双层膜的重排。这种脂质分选招募信号分子并触发吞噬和树突状细胞活化。因此，我们以前的工作将力和物理干扰的概念引入免疫激活领域。在这项建议中，我们大大推进了这一概念。我们提供的证据表明，调节性T细胞，一组对控制自身免疫至关重要的CD4+ T细胞，与树突状细胞强烈结合，抑制后者进行不必要的免疫激活的能力。此外，我们发现吞噬作用可以通过受体独立的膜脂源信号传导启动，作为固体颗粒摄取的通用平台。我们建议使用AFM与成像仪器耦合来进一步研究这些相互作用的基本参数和与这些生物物理变化相关的信号事件。这项工作的结果将打开免疫学研究的新一页，并介绍生物物理学作为免疫调节的一个重要方面。这项工作将帮助我们了解膜生物学的几个基本方面，以及细胞膜脂质如何影响免疫信号转导。这将进一步导致我们更好地控制免疫细胞活化，这是加拿大人口健康的中心。

Historically, immunological research has been a protein-centric endeavor, with signaling events often defined as biochemical changes of polypeptides. How biophysical factors play into this scheme has been mostly overlooked. Funded by our last NSERC grant, we have used atomic force microscopy (AFM)-based single cell force spectroscopy (SCFS) to elucidate several important immunological events that are driven by biophysical changes at the cell membrane. We have found that solid substances engage surface lipids with substantial intensity, causing rearrangement of the bilayer membrane. This lipid sorting recruits signaling molecules and triggers phagocytosis and dendritic cell activation. Our previous work therefore introduces the concept of force and physical disturbance into the realm of immune activation. In this proposal, we substantially move this concept forward. We provide evidence that regulatory T cells, a group of CD4+ T cells essential to control autoimmunity, bind strongly to dendritic cells and suppress the latter's ability to mount unwanted immune activation. In addition, we have found that phagocytosis can be initiated via a receptor independent, membrane lipid originated signaling, serving as a generic platform for solid particle uptake. We propose to use AFM coupled to imaging instrument to further study the essential parameters of these interactions and signaling events associated with these biophysical changes. The outcomes of this work will open a new page in immunological research, and introduce biophysics as an essential aspect of immune regulation. The proposed work will help us understand several fundamental aspects of membrane biology and how cell membrane lipids impact immune signal transduction. This will further lead to our better control of immune cell activation that is at the centre of population health in Canada.