Regulation of integrin LFA-1 during T cell migration and activation

描述(申请人提供)：T细胞花大部分时间在淋巴器官中寻找由抗原提呈细胞(APC)呈递的同源抗原，并迅速通过血流循环到另一个淋巴结。细胞外渗通过高内皮微静脉(HEV)发生，并依赖于几个关键事件，包括趋化因子配体CCL19/21激活趋化因子受体CCR7以及整合素LFA-1(CD11a/CD18)与其配体ICAM-1的黏附。T细胞必须变得高度迁移，才能利用迁移T细胞前沿的活性LFA-1，扫描密集排列的器官以寻找其在APC上的同源抗原。当抗原攻击时，T细胞与APC形成稳定的相互作用，这被称为免疫突触(IS)。活化的LFA-1被重新定位到IS，稳定T细胞和APC之间的相互作用。尽管LFA-1是迁移和IS形成的关键粘附力，但趋化因子和T细胞受体(TCR)信号转导的结果是完全不同的，因为前者诱导GO，后者介导Stop信号。我们假设T细胞收到的趋化因子和TCR信号的大小将决定LFA-1介导的相互作用的结果，从而决定T细胞的激活。为了研究LFA-1在T细胞活化和迁移中的作用，我们建立了荧光敲入(KI)小鼠，使我们能够可视化LFA-1的表达、分布和激活模式。使用OTI TCR转基因小鼠和改变的多肽配体(APL)系统，我们将测量LFA-1在不同TCR信号强度激活的T细胞中的重新分布和激活。这将使我们能够确定TCR信号强度对LFA-1重分布的影响 在迁移中，T细胞被引导经历IS形成(目标1)。我们还将加入一种可光激活的趋化因子受体PA-CCR7，以评估趋化因子信号强度对LFA-1激活的影响(目标2)。通过结合这些技术，我们将测试趋化因子依赖和TCR依赖信号之间的平衡是否决定了LFA-1的分布和功能，以及平衡受体竞争以确保迁移T细胞与参与免疫突触的激活T细胞准确利用LFA-1的机制。

DESCRIPTION (provided by applicant): T cells spend the majority of their time perusing lymphoid organs in search of cognate antigen presented by antigen presenting cells (APCs) and quickly recirculating through the bloodstream to another lymph node. Extravasation into a given lymph node occurs through high endothelial venules (HEV) and is dependent upon several key events, including activation of chemokine receptor CCR7 by chemokine ligands CCL19/21 and adhesion of integrin LFA-1 (CD11a/CD18) to its ligand ICAM-1. T cells must become highly migratory to scan the densely packed organ for their cognate antigen on APC, utilizing active LFA-1 at the leading edge of a migrating T cell. Upon antigen challenge, a T cell forms a stable interaction with the APC, which is known as the immunological synapse (IS). Active LFA-1 is relocated to the IS, stabilizing the interaction between the T cell and APC. Although LFA-1 is a key adhesive force for both migration and IS formation, the outcome of chemokine and T cell receptor (TCR) signaling is quite different, as the former induce "go" and the latter mediate "stop" signals. We hypothesize that the magnitude of chemokine and TCR signals received by the T cell will determine the outcome of LFA-1 mediated interactions and thus T cell activation. To investigate the role of LFA-1 during T cell activation and migration, we generated fluorescent knock-in (KI) mice that will allow us to visualize expression, distribution, and activation pattern of LFA-1. Using OTI TCR transgenic mice together with an altered peptide ligand (APL) system, we will measure LFA-1 redistribution and activation in T cells activated by varying TCR signal strength. This will allow us to determine the effect of TCR signal strength on LFA-1 redistribution in migrating T cells directed to undergo IS formation (Aim 1). We will also incorporate a photoactivatable chemokine receptor, PA-CCR7, to assess the effect of chemokine signal strength on LFA-1 activation (Aim 2). By combining these techniques, we will test whether the balance between chemokine-dependent versus TCR-dependent signals dictates LFA-1 distribution and function, as well as the mechanism balancing the receptor competition to ensure accurate LFA-1 utilization in a migrating T cell versus an activating T cell engaged in an immunological synapse.