Antigen Presentation to Self-reactive T Cells in Human Autoimmune Diseases

该项目的目标是确定抗原呈递和T细胞识别机制 负责多发性硬化症中髓鞘特异的CD4T细胞的激活在这一资助期间，PI的实验室 确定了第一个人类自身免疫性TCR的晶体结构，并发现了一种不寻常的TCR结合 拓扑学。生化研究表明该TCR与其自体多肽/MHC之间存在低亲和力的相互作用 复杂，与结构中观察到的次优结合模式一致。这样的次优绑定 模式可能有助于逃避胸腺和外周的耐受诱导，因为相关的 抗原提呈细胞表达有限数量的自身抗原。表达该TCR的转基因小鼠 然而，人类MHC限制性元件在很高的水平上发展为自发的自身免疫 发病率，表明这些T细胞具有识别/信号机制，至少部分 补偿改变的TCR与自体肽/MHC的相互作用。成像研究表明 两种不同髓鞘特异性形成的免疫突触的组织结构有很大差异 人类T细胞克隆与两个抗病毒T细胞克隆的比较。 在下一个资助期，我们将确定更改后的TCR确认属性如何影响 免疫突触的形成和由此产生的信号事件。在目标1中，我们将定义 免疫突触形成的机制通过研究突触形成的动力学， 关键信号分子的招募、信号持续时间以及终止机制 通过TCR内化传递信号。我们的假设是，次优的TCR结合属性会延迟TCR 运输到突触中心，在那里TCR被内化，从而延长了最初较弱的 激活信号。在目标2中，我们将研究这些变化如何定量地改变 自身反应性T细胞与抗病毒T细胞中特定的信号通路，目的是识别信号 这些分子对自身反应性T细胞的激活至关重要，但对抗病毒T细胞来说却是必不可少的。在……里面 目的3，我们将研究是否仍然可以通过靶向传递诱导对这种T细胞的耐受 通过抗体-多肽融合蛋白将自体多肽转化为专门的淋巴结基质细胞 外围设备容忍度。

The goal of the project is to define the antigen presentation and T cell recognition mechanisms responsible for the activation of myelin-specific CD4 T cells in MS. During this funding period, the Pi's lab determined the crystal structure of the first human autoimmune TCR and identified an unusual TCR binding topology. Biochemical studies demonstrated a low affinity interaction of this TCR with its self-peptide/MHC complex, consistent with the suboptimal binding mode observed in the structure. Such a suboptimal binding mode may facilitate escape from tolerance induction in the thymus and periphery because the relevant antigen presenting cells express limiting quantities of self-antigen. Transgenic mice that express this TCR and the human MHC restriction element nevertheless develop spontaneous autoimmunity at a high incidence, indicating that these T cells have recognition/signaling mechanisms that at least partially compensate for the altered TCR interaction with self-peptide/MHC. Imaging studies demonstrated substantial differences in the organization of immunological synapses formed by two different myelin-specific human T cell clones compared to two anti-viral T cell clones. During the next funding period, we will determine how the altered TCR recognition properties affect the formation of immunological synapses and resulting signaling events. In Aim 1, we will define the mechanisms of immunological synapse formation by examining the kinetics of synapse formation, the recruitment of key signaling molecules, the duration of signaling as well as the mechanisms that terminate signaling by TCR internalization. Our hypothesis is that the suboptimal TCR binding properties delay TCR transport to the synapse center where TCR is internalized, thus extending the duration of the initially weaker activation signal. In Aim 2, we will examine how these changes quantitatively modify the contribution of particular signaling pathways in self-reactive versus anti-viral T cells, with the goal of identifying signaling molecules that are critical for the activation of self-reactive T cells but dispensable for anti-viral T cells. In Aim 3, we will examine whether tolerance can nevertheless be induced for such T cells by targeted delivery of the self-peptide via an antibody-peptide fusion protein to lymph node stromal cells specialized in peripheral tolerance.