CONTROL OF PERIPHERAL T CELL FUNCTION BY SELF-PEPTIDE/MHC

T细胞通过其T细胞受体(TCR)识别抗原是诱导 适应性免疫反应。TCR识别抗原表面的外来肽/MHC复合体 然而，自体多肽/MHC复合体也发挥着关键作用。这些自我pMHC相互作用 是胸腺中T细胞的阳性选择所必需的，以产生MHC限制性谱系和阴性 选择清除自身反应性T细胞。在外周T细胞中，TCR：自身pMHC相互作用是 对生存、设定信号阈值和对外来抗原的反应至关重要。TCR 对自身pMHC复合体的识别本质上很弱，但仍会导致T细胞中的信号事件。APC 如树突状细胞在其表面表达数千种不同的自身pMHC复合体，使 研究T细胞中被刺激的信号的性质。我们的新方法利用TCR 对自身pMHC的不同亲和力，这将使我们能够识别出一种增强T细胞活力和 活体内的反应。具体地说，我们已经产生了两只TCR转基因小鼠，LLO56和LLO118，它们都 识别免疫优势李斯特菌表位(LLO)。研究这两个T细胞的好处是它们 对李斯特菌感染有不同的体内行为。此外，这也是一个中心点 应用是LLO118和LLO56的本征灵敏度由自身的pMHC设置和维护，具有 LLO56T细胞具有较强的自身pMHC相互作用。我们最初的活体实验表明 它们在淋巴组织中的转运时间的差异，表明对自身多肽的识别是主要的 T细胞运动的决定因素。该提案测试假设是显示了一组自我pMHC 在体内与LLO56和LLO118 T细胞进行特异性但微弱的相互作用。这些 相互作用设定了信号阈值，对T细胞的功能和生存至关重要。为了测试这一点 假设，提出了两个具体目标。在目标1中，我们建议鉴定能够增强T：DC的自身pMHC 在没有抗原的情况下相互作用。我们开发了一种新型的小型自我pMHC曲目系统，在其中 我们可以表达3到9个定义的共价连接的自体pMHC作为DC上唯一的II类分子。我们会 用双光子显微镜在体内测试一系列(最多30个)自身pMHC减缓运动的能力 LLO56或LLO118 T细胞。在目标2中，我们将确定其特异性和体内功能结果。 自身pMHC：T细胞相互作用。将分析目标1中确定的主动自我pMHC的具体程度 它们被T细胞识别。然后，将研究主动自我pMHC是否具有增强AN的能力 体内对外来抗原的反应。通过识别一个活跃的自我pMHC，在未来的研究中使用这个定义 系统中，这些自身pMHC诱导的T细胞内的信号通路可以被阐明。了解这些 途径及其如何被激活，可能导致T细胞的药理增强作用的发展 细胞的存活和功能。

The recognition of antigen by a T cell through its T cell receptor (TCR) is a seminal event in the induction of an adaptive immune response. The TCR recognizes a foreign peptide/MHC complex on the surface of an antigen presenting cell; however, self-peptide/MHC complexes also play a critical role. These self-pMHC interactions are needed for positive selection of T cells in the thymus to generate a MHC restricted repertoire and negative selection to purge the repertoire of self-reactive T cells. In peripheral T cells TCR:self-pMHC interactions are critical for survival, for setting signaling thresholds, and for responses to foreign antigens. The TCR recognition of self-pMHC complexes is weak in nature, but still results in signaling events in the T cell. An APC such as a dendritic cell expresses thousands of different self-pMHC complexes on its surface, complicating the investigation of the nature of the signals stimulated in the T cell. Our novel approaches leverage TCRs with distinct affinities for a self-pMHC, which will allow us to identify a self-pMHC that augments T cell motility and responses in vivo. Specifically, we have generated two TCR transgenic mice, LLO56 and LLO118, which both recognize the immunodominant Listeria epitope (LLO). The advantage of studying these two T cells is that they have distinct in vivo behaviors in response to Listeria infection. Moreover, and a central point for this application, is that the intrinsic sensitivity of LLO118 and LLO56 is set and maintained by self pMHC, with the LLO56 T cells having stronger self-pMHC interactions. Our initial in vivo experiments indicate marked differences in their transit times in lymphoid tissues, pointing to the recognition of self peptides as a major determinant of T cell motilities. The hypothesis this proposal tests is that there is a set of self-pMHC displayed on an APC, which make specific, but weak, interactions with LLO56 and LLO118 T cells in vivo. These interactions set the signaling threshold and are essential for T cell function and survival. To test this hypothesis, two specific aims are proposed. In aim 1, we propose to Identify self-pMHCs that potentiate T:DC interactions in the absence of antigen. We have developed a novel mini-self-pMHC repertoire system in which we can express 3 to 9 defined covalently linkered self-pMHC as the only class II molecules on a DC. We will test a series (up to 30) of self-pMHC in vivo using 2-photon microscopy for their abilities to slow the motility of LLO56 or LLO118 T cells. In Aim 2, we will determine the specificity and in vivo functional consequences of self-pMHC:T cell interactions. The active self-pMHC identified in Aim 1, will be analyzed for how specifically they are recognized by the T cells. The active self-pMHC will then be studied for their ability to augment an in vivo response to foreign antigen. By identifying an active self-pMHC, in future studies using this defined system, the signaling pathways in T cells induced by these self-pMHC can be elucidated. Knowing these pathways and how they are activated, could lead to the development of pharmacological enhancements for T cell survival and function.