Identifying Mechanisms Governing T Cell Diversity

项目总结 适应性免疫系统的特点是多样性和记忆性。多样化的T细胞谱系对于 确保有效防御几乎无限数量的潜在病毒、真菌和细菌病原体。T 细胞多样性产生于胸腺。由于T细胞受体组装不精确，超过108个T细胞克隆 在胸腺中产生，每个都表达一个独特的T细胞受体。在成年早期，胸腺 渐开线。因此，为了维持健康的免疫系统，T细胞的多样性必须在 免疫外周。维持T细胞多样性需要微调，因为在 随着时间的推移，T细胞库可能会对T细胞多样性产生巨大影响。每个克隆必须由支持 积极的动态平衡信号，使其能够存活数十年。同时，每个克隆人都不能 过度增殖。由于免疫空间似乎是固定的，单个T细胞的过度扩张 克隆人可能会排挤它的邻居。尽管T细胞动态平衡对 对于人类健康和疾病，我们缺乏对T细胞多样性如何维持的机械性洞察力。有两个 取得进展的重要障碍。首先，人体研究往往集中在相对较小、无关的研究上 表型不同的老年人的队列。其次，对复杂非均质的研究 细胞群体需要单细胞分辨率的分析。为了克服这些障碍，我们建议研究一项 表型相似的人类异常值队列，他们的T细胞谱系发生了深刻的变化，即 皮肤T细胞淋巴瘤(CTCL)患者。CTCL是一种无法治愈的皮肤非霍奇金淋巴瘤- 归巢的CD4T细胞。晚期白血病CTCL患者总是出现细胞过度增殖 恶性T细胞克隆和良性的、未转化的CD4和CD8T细胞的严重损失。这 淋巴细胞减少是疾病的一个特征，以一种阶段依赖的方式发展，并不可避免地 IV期患者。据推测，正常T细胞的丧失通过抑制肿瘤细胞而使其受益 抗肿瘤免疫。新出现的数据表明，这两种相反的趋势是由于病理性的 维持克隆存活的体内平衡信号的变化和阻止克隆 使人口过度拥挤。我们假设CTCL肿瘤细胞有阳性的过度激活。 动态平衡信号和对负向动态平衡信号的抵抗。相反，正在消失的、良性的 CTCL患者的T细胞对正稳态信号具有相对抵抗力，对 CTCL细胞产生的负稳态信号。为了阐明疾病的机制，我们将使用高- 基于维度发现的方法来识别和功能验证支配高优先级分子 T细胞动态平衡。我们相信，成功完成这项提议将确定重要的动态平衡。 在健康和其他疾病中对T细胞动态平衡至关重要的信号机制。

PROJECT SUMMARY The hallmarks of the adaptive immune system are diversity and memory. A diverse T cell repertoire is critical to ensure an effective defense against a near infinite number of potential viral, fungal, and bacterial pathogens. T cell diversity is generated in the thymus. Due to imprecise T cell receptor assembly, over 108 T cell clones are produced in the thymus, each expressing a unique T cell receptor. During early adulthood, the thymus involutes. Therefore, to maintain a healthy immune system, T cell diversity has to be sustained in the immunological periphery. Maintenance of T cell diversity requires fine tuning because small perturbations in the T cell pool can have dramatic effects over time on T cell diversity. Each clone must be supported by positive homeostatic signals that enable survival over decades. At the same time, each clone must not overproliferate. Because the immunological space appears to be fixed, overexpansion of individual T cell clones can potentially crowd out its neighbors. Despite the fundamental importance of T cell homeostasis to human health and disease, we lack mechanistic insight into how T cell diversity is maintained. There are two important barriers to progress. For one, human studies have often focused on relatively small, unrelated cohorts of phenotypically heterogeneous aged individuals. Secondly, the study of a complex heterogeneous cell population requires assays with single cell resolution. To overcome these barriers, we propose to study a phenotypically similar cohort of human outliers who have profound alterations in their T cell repertoire, namely patients with cutaneous T cell lymphoma (CTCL). CTCL is an incurable non-Hodgkin lymphoma of the skin- homing CD4+ T cell. Patients with advanced leukemic CTCL invariably develop overproliferation of the malignant T cell clone and profound losses of the benign, untransformed CD4+ and CD8+ T cells. This lymphopenia is a characteristic feature of disease, develops in a stage-dependent manner, and is inevitable in patients with Stage IV disease. Presumably, the loss of normal T cells benefits the tumor cells by inhibiting anti-tumor immunity. Emerging data suggest that these two antiparallel trends occur due to pathological alterations in the homeostatic signals that keep clones alive and the homeostatic signals that keep clones from overcrowding the population. We hypothesize that the CTCL tumor cells have hyperactivation of the positive homeostatic signals and resistance to the negative homeostatic signals. Conversely, the disappearing, benign T cells in CTCL patients are relatively resistant to the positive homeostatic signals and highly sensitive to the negative homeostatic signals produced by CTCL cells. To elucidate disease mechanisms, we will use high- dimension discovery based approaches to identify and functionally validate high priority molecules that govern T cell homeostasis. We believe that successful completion of this proposal will identify important homeostatic signaling mechanisms that are fundamentally important for T cell homeostasis in health and in other diseases.