Linking T cell receptor sequence to T cell function

将 T 细胞受体序列与 T 细胞功能联系起来

• 批准号: RGPIN-2016-03808
• 负责人: Mandl, Judith
• 金额: $ 2.62万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=658632
• 关键词: Linking; cell; receptor; sequence; function

T cells are critical effector cells of the adaptive immune system which recognize foreign antigen in the form of peptides presented by host cell major histocompatibility complexes (MHC). Each T cell bears a unique antigen recognition receptor, the T cell receptor (TCR), which determines the exquisite specificity and the affinity with which an individual T cell binds peptide-MHC. The TCR is generated through rearrangement of germline encoded gene segments and the addition of non-templated (non-germline encoded) nucleotides by an enzyme called terminal deoxynucleotidyl transferase (TdT). The interaction strength between the TCR and peptide-MHC is a critical parameter in all T cell fate decisions, from selection in the thymus during development to differentiation during infection. Yet, due to the enormous diversity of TCRs that can be made (>1015 distinct receptors), predicting functional characteristics of a T cell from its TCR sequence is an unsolved challenge. Moreover, while the enormous TCR diversity within a T cell repertoire that is added by TdT during TCR gene segment rearrangement is thought to be essential in effective host protection, this has not been demonstrated experimentally. Thus, the link between TCR sequence diversity, pMHC binding strength, and T cell function in host protection remains unclear.****To date, it has been difficult to discern global patterns in TCR sequence or binding affinity for a T cell population without prior knowledge of the range of peptide-MHC ligands for each TCR. To overcome this limitation, we propose a novel approach that interrogates the impact of the TCR sequence on T cell function in an unbiased manner. We previously described that T cell expression of the membrane protein CD5 is directly proportional to the strength of the TCR signal obtained from self-ligands as well as foreign antigens presented in the context of MHC. Thus, by sorting CD4 T cells into CD5hi and CD5lo populations, we can now investigate properties of TCR sequences with distinct binding strengths for peptide-MHC without requiring prior knowledge of the peptides that they recognize. We hypothesize that CD5hi cells contain predominantly germline-encoded TCRs that are evolutionarily conserved to bind foreign peptide-MHC that we frequently encounter as a species. In contrast, we predict that CD5lo cells are enriched for TdT-dependent TCRs to provide the additional diversity that is required to respond to new and divergent pathogens. We will determine whether lower affinity TCRs that are generated by TdT-mediated junctional nucleotide additions play a fundamentally different role in the immune system than do high affinity TCRs. Overall, my research program will provide fundamental insight into the quantitative and qualitative features of an effective T cell repertoire and shed light on the evolutionary pressures that led to the use of TdT to increase TCR diversity.**

T细胞是适应性免疫系统的关键效应细胞，其识别由宿主细胞主要组织相容性复合物（MHC）呈递的肽形式的外来抗原。每个T细胞具有独特的抗原识别受体，即T细胞受体（TCR），其决定单个T细胞结合肽-MHC的精确特异性和亲和力。TCR通过种系编码的基因片段的重排和通过称为末端脱氧核苷酸转移酶（TdT）的酶添加非模板化（非种系编码）核苷酸来产生。TCR和肽-MHC之间的相互作用强度是所有T细胞命运决定的关键参数，从发育期间胸腺中的选择到感染期间的分化。然而，由于可以产生的TCR的巨大多样性（>1015个不同的受体），从其TCR序列预测T细胞的功能特征是一个未解决的挑战。此外，虽然在TCR基因片段重排期间由TdT添加的T细胞库内的巨大TCR多样性被认为是有效宿主保护所必需的，但这尚未通过实验证明。因此，TCR序列多样性、pMHC结合强度和T细胞在宿主保护中的功能之间的联系仍不清楚。迄今为止，在没有每个TCR的肽-MHC配体范围的先验知识的情况下，难以辨别TCR序列或对T细胞群体的结合亲和力的全局模式。为了克服这一局限性，我们提出了一种新的方法，询问的TCR序列对T细胞功能的影响，在一个公正的方式。我们先前描述了膜蛋白CD 5的T细胞表达与从自身配体以及在MHC背景下呈递的外来抗原获得的TCR信号的强度成正比。因此，通过将CD 4 T细胞分选成CD 5 hi和CD 5lo群体，我们现在可以研究TCR序列对肽-MHC具有不同结合强度的性质，而不需要它们识别的肽的先验知识。我们假设，CD 5 hi细胞主要含有种系编码的TCR，这些TCR在进化上保守，以结合我们作为一个物种经常遇到的外源肽-MHC。相比之下，我们预测CD 5 lo细胞富含TdT依赖性TCR，以提供应对新的和不同的病原体所需的额外多样性。我们将确定由TdT介导的连接核苷酸添加产生的低亲和力TCR是否在免疫系统中发挥与高亲和力TCR根本不同的作用。总的来说，我的研究计划将提供有效T细胞库的定量和定性特征的基本见解，并阐明导致使用TdT增加TCR多样性的进化压力。