Molecular Recognition of Ligand by the gamma delta T cell Receptor

描述(申请人提供)：D T细胞是针对感染性疾病和癌变的免疫反应的重要组成部分，但它们通过其体细胞重组T细胞受体(TCR)检测抗原的生化机制尚不清楚。与仅限于识别主要组织相容性复合体(MHC)分子中的抗原的TCR不同，~D TCR可以识别从自身MHC到完整、未加工的病毒糖蛋白的各种配体。虽然~D TCR在结构上与αTCR相似，并且都使用CD3信号复合体的成分进行信号转导，但很明显，~D TCR以一种截然不同的不同方式与抗原结合。缺乏这些受体的具体生化特征及其与配体的相互作用，阻碍了人们对这些受体在T细胞激活中的作用的真正了解。因此，这项建议的长期目标是了解D TCR参与的生化和结构机制，以及这种结合事件如何区分健康和不健康的组织以启动T细胞激活。我们计划使用两种直接互补但又独特的平行策略来研究这些问题。第一种是基于结构/功能的方法，将生物化学、结构生物学和基于细胞的功能分析相结合，以确定管理TCR识别所定义配体的特定分子细节。我们将把我们的生化、生物物理和结构研究集中在两个受体/配体的相互作用上：1)小鼠MHC T107T22分子和2)人MHC CD1c分子的D TCRs。第二种方法涉及使用基于跨物种序列的分析来理解形成D TCRV、D和J基因库的选择性进化机制。这种方法将定义哪些类型的选择压力(多样化、中性或纯化)主导了这些基因在人类和非人类灵长类动物中的进化，表明了它们与之结合的配体的性质。这些方法将有助于阐明D T细胞受体相互作用的分子识别原理，并确定D T细胞受体是否以一种收敛的方式识别配体，如TCR/MHCp相互作用中所见，或者是否存在不同的识别方案，对于每个D T细胞群体和特定的配体是独特的。

DESCRIPTION (provided by applicant): ?d T cells constitute an important component of the immune response against infectious agents and cancerous transformations, yet the biochemical mechanisms by which they detect antigen through their somatically recombined T cell receptor (TCR) remain unclear. Unlike a¿TCRs, which are restricted to recognizing antigens in the context of Major Histocompatibility Complex (MHC) molecules, ?d TCRs can recognize a diversity of ligands ranging from self MHC to intact, unprocessed, viral glycoproteins. While the ?d TCR is structurally similar to the a¿TCR, and both use components of the CD3 signaling complex for signal transduction, it is clear ?d TCRs bind antigen in a distinct and divergent way. The lack of concrete biochemical characterization of these receptors and their interactions with ligands has hindered a true understanding of the role of these receptors in ?d T cell activation. Thus, the long-term goal of this proposal is to understand the biochemical and structural mechanisms of ?d TCR engagement and how this binding event discriminates between healthy and unhealthy tissue to initiate T cell activation. We plan to study these questions using two parallel strategies that are directly complementary, yet unique. The first is a structure/function-based approach combining biochemistry, structural biology and cell-based functional assays to determine the specific molecular details that govern ?d TCR recognition of defined ligands. We will focus our biochemical, biophysical and structural studies on two receptor/ligand interactions: ?d TCRs specific for 1) the murine MHC T107T22 molecules and 2) the human MHC CD1c molecules. The second approach involves using a cross-species sequence-based analysis to understand the selective, evolutionary mechanisms that shape the ?d TCR V, D and J gene repertoire. This approach will define what types of selective pressures (diversifying, neutral or purifying) have governed the evolution of these genes in humans and non-human primates, indicating the nature of the ligands to which they bind. These approaches, together, will help to elucidate the molecular recognition principles of ?d TCR interactions, and determine if ?d TCRs recognize ligands in a convergent manner, such as seen in a¿ TCR/MHCp interactions, or whether there are a diversity of recognition solutions, unique to each ?d T cell population and particular ligand.