Identifying Mechanisms Governing T Cell Diversity

项目摘要 适应性免疫系统的特点是多样性和记忆。多样化的T细胞库对于 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。不 细胞多样性在胸腺中产生。由于不精确的T细胞受体组装，超过108个T细胞克隆被克隆。 在胸腺中产生，每一种都表达一种独特的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细胞多样性必须在免疫系统中维持。 免疫外周。T细胞多样性的维持需要微调，因为细胞内的小扰动， T细胞库可随时间对T细胞多样性产生显著影响。每个克隆都必须由 积极的自我平衡信号，使生存几十年。同时，每个克隆体不得 过度增殖由于免疫空间似乎是固定的，单个T细胞的过度扩增， 克隆体有可能排挤它的邻居。尽管T细胞内稳态对免疫应答的重要性 在人类健康和疾病方面，我们缺乏对T细胞多样性如何维持的机械见解。有两 进步的重要障碍。首先，人类研究往往集中在相对较小的，无关的， 表型异质性老年个体的队列。其次，研究了复杂的异质性 细胞群体需要具有单细胞分辨率的测定。为了克服这些障碍，我们建议研究一个 表型相似的人类离群者队列，其T细胞库发生了深刻的变化，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CD 4 + T细胞。患有晚期白血病CTCL的患者总是发展成 恶性T细胞克隆和良性、未转化的CD 4+和CD 8 + T细胞的严重损失。这 淋巴细胞减少症是疾病的特征性特征，以阶段依赖性方式发展，并且在 IV期疾病患者。据推测，正常T细胞的损失通过抑制肿瘤细胞的生长而有益于肿瘤细胞。 抗肿瘤免疫新出现的数据表明，这两个反平行的趋势发生，由于病理性 保持克隆存活的自我平衡信号和保持克隆 人口过剩。我们假设CTCL肿瘤细胞过度激活了阳性信号， 稳态信号和对负稳态信号的抗性。相反，消失的，良性的 CTCL患者中的T细胞对阳性稳态信号相对抵抗，并且对免疫应答高度敏感。 CTCL细胞产生的负稳态信号。为了阐明疾病机制，我们将使用高- 基于维度发现的方法来识别和功能验证高优先级分子， T细胞稳态。我们相信，成功完成这一提案将确定重要的稳态 这些信号传导机制对于健康和其他疾病中的T细胞稳态至关重要。

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.