Probing the effect of dendritic cell co-stimulatory ligand lateral mobility on T cell mediated immunity and tolerance

免疫系统保护我们免受病毒和细菌等外部病原体的影响，也保护我们免受癌细胞等内部治疗的影响。免疫系统功能的核心是它将这些食物与我们身体中大量无害的细胞区分开来的能力。免疫系统的两种不同类型的细胞，称为树突状细胞(DC)和T细胞，在这一过程中至关重要。DC充当哨兵和信使。它们不断地采集周围环境、无害细胞和病原体的样本，消化它们，并将这些消化的部分呈现在它们的表面，以识别潜在的威胁。在这个过程中，来自环境的提示和信号会导致DC变得成熟或耐受。成熟树突状细胞和耐受性树突状细胞都与T细胞通信，T细胞通过形成紧密的细胞-细胞接触来识别树突状细胞表面的识别符，称为免疫突触。与成熟DC相互作用的T细胞将被激活，开始增殖，最终攻击并消除治疗，这一过程被称为免疫。相比之下，产生耐受性的DC指示T细胞变得无反应，导致我们的免疫系统在一个称为耐受性的过程中忽略被识别的实体的来源，该实体被认为是无害的。重要的是，人类的许多疾病都是由免疫和耐受性调节不当引起的。例如，癌症能够指示DC产生耐受性，导致逃避我们的免疫系统和转移。相反，成熟的DC意外地将健康细胞识别为威胁，导致免疫反应，这是许多自身免疫性疾病的原因，免疫系统攻击我们自己的身体。因此，全面了解成熟DC和耐受性DC的不同特性如何导致T细胞应答或无应答，是开发有效的自身免疫性疾病疫苗、免疫疗法和治疗方法的重要课题。成熟树突状细胞和耐受树突状细胞的不同特性在一定程度上是由它们表面携带的一组特定的蛋白质类型来解释的，这些蛋白质类型用于沟通和指示T细胞。这些蛋白质中的每一种都被T细胞上的对应蛋白识别，触发T细胞中的内部信号，这些信号有助于免疫或耐受。然而，先前的研究表明，在这一过程中，重要的不仅仅是特定蛋白质的存在或不存在。DC似乎也能够控制这些蛋白质在其表面的运动，要么允许它们自由移动，要么将它们固定在特定位置。这反过来又改变了T细胞上特定类型的蛋白质被相应蛋白质识别的方式，并影响了它们的信号。因此，本项目的目的是详细、全面和比较地研究树突状细胞上的蛋白质流动性如何影响免疫和耐受之间的决定。为此，我们将使用一种我们开发的新型人造底物来专门控制不同类型蛋白质的流动性，即一些将是可移动的，而另一些将是固定的。这将使我们能够以完全受控的方式模拟DC的表面，并研究广泛选择的特定类型蛋白质的流动性的影响。此外，我们将测量成熟和耐受树突状细胞表面的蛋白质迁移率，并在模拟人类组织复杂性的三维设置中表征它们与T细胞的免疫突触。此外，为了补充我们来自人工底物的结果，我们将通过基因工程改变成熟和耐受树突状细胞中特定类型蛋白质的流动性，并测量这如何影响T细胞的相互作用和指导。总之，这将使我们对蛋白质流动性在免疫和耐受之间的决定中的作用有一个广泛的理解，有可能为治疗干预开辟新的途径。

The immune system protects us from outside pathogens like viruses and bacteria, but also from internal treats like cancerous cells. Central to the function of the immune system is its capability to discriminate these treats from the vast number of harmless cells of our own bodies. Two distinct cell types of the immune system, termed dendritic cells (DCs) and T cells, are crucial to this process. DCs act as sentinels and messengers. They constantly take samples of their surroundings, harmless cells and pathogens alike, digest them and present these digested parts on their surface to identify potential threats. During this process, cues and signals from their environment lead DCs to become either mature or tolerogenic. Both, mature and tolerogenic DCs, communicate with T cells that recognise the identifier on the DC's surface by forming a close cell-cell contact, termed an immunological synapse. T cells that interact with mature DCs will become activated, start to multiply and finally attack and eliminate the treat, a process termed immunity. In contrast, tolerogenic DCs instruct T cells to become non-responsive, leading our immune system to ignore the source of the identified entity, which is deemed harmless, in a process termed tolerance. Importantly, many diseases in humans are caused by a mis-regulation of immunity and tolerance. Cancers for example, are able to instruct DCs to become tolerogenic, leading to escape from our immune system and metastasis. Conversely, the accidental identification of a healthy cell as a threat by mature DCs, leading to an immune response, is the cause for many autoimmune diseases where the immune system attacks our own body. Therefore, a comprehensive understanding of how the different properties of mature DCs and tolerogenic DCs lead to T cell responses or non-responses is an important topic in developing effective vaccines, immunotherapies and cures for autoimmune diseases. The different properties of mature and tolerogenic DCs are in part explained by the particular set of protein types that they carry on their surface to communicate and instruct T cells. Each of these proteins is recognised by its counterpart on T cells, triggering internal signals in the T cell that either contribute to immunity or tolerance. However, previous research suggests that it is not only the mere presence or absence of particular proteins that matters in this process. DCs also seem to be able to control the movement of these proteins on their surface, either allowing them to move freely or fixing them to certain positions. This in turn, changes how individual types of proteins are recognised by their counterparts on T cells and influences their signals. Consequently, the aim of this project is to study how protein mobility on DCs influences the decision between immunity and tolerance in a detailed, comprehensive and comparative manner. To this end we will employ a novel, artificial substrate that we developed to specifically control the mobility of different types of proteins i.e. some will be mobile while others will be immobile. This will allow us to emulate the surface of DCs in a fully controlled manner and to study the effect of mobility of a broad selection of specific types of proteins. In addition, we will measure protein mobility on the surface of mature and tolerogenic DCs and characterize their immunological synapses with T cells in a three-dimensional setup that mimics the complexity of human tissue. Additionally, and to complement our results from the artificial substrates, we will alter the mobility of specific types of proteins in mature and tolerogenic DCs by genetic engineering and measure how this affects the interaction and instruction of T cells. Together, this will give us an extensive understanding of the role of protein mobility in the decision between immunity and tolerance, potentially opening up new avenues for therapeutic interventions.