Immune Reconstitution

免疫重建

• 批准号: 9556308
• 负责人: Ronald Gress
• 金额: $ 130.34万
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9556308
• 关键词: Acute; Address; Adult; Aging; Allogenic; Androgens; Area; Biology; CD4 Positive T Lymphocytes; CD8-Positive T-Lymphocytes; CD8B1 gene; Cell Aging; Cell Compartmentation; Cell Cycle Regulation; Cell Proliferation; Cell surface; Cells; Clinical Trials; Complex; Distal; Dose; Emigrant; Epithelial Cells; Genes; Goals; Hematopoietic Stem Cell Transplantation; Homeostasis; Human; Immune; Immune system; Immunity; Impairment; Injury; Insulin-Like Growth Factor I; Interleukin 7 Receptor; Interleukin-7; Ligands; Maintenance; Malignant Neoplasms; Maps; Mediating; Modeling; Molecular; Natural regeneration; Pathway interactions; Patients; Pattern; Peripheral; Phenotype; Population; Premature aging syndrome; Proteins; Recovery; Regulation; Research; Role; Signal Pathway; Signal Transduction; Stromal Cells; T-Lymphocyte; T-Lymphocyte Subsets; TP53 gene; Thymic epithelial cell; Thymocyte Development; Thymus Gland; Time; Tissues; Transgenic Organisms; Transplantation; Vaccines; Work; cancer therapy; chemotherapy; cytokine; functional disability; interest; liquid chromatography mass spectrometry; mouse model; notch protein; novel strategies; reconstitution; senescence; thymocyte; time interval

The biology of reconstitution of T cell populations following acute loss remains incompletely characterized. Using murine models, we first identified two primary pathways of T cell immune reconstitution, the classic, thymic-dependent pathway, and a second, thymic-independent pathway. We then identified T cell surface markers which allowed identification, by phenotyping of reconstituted T cell populations, of the pathways which had given rise to them, and then applied this information to the characterization of T cell reconstitution in patients. Initial work established the applicability of this approach to the study of T cell population regeneration in humans who were young. Recent work verified validity of the approach and established the course of T cell immune reconstitution in adult humans over an extended period time for each of the two primary pathways. This work showed an essential role for the thymus in regenerating CD4+ T cells quantitatively. CD8+ T cells can numerically be reconstituted by peripheral expansion for immune reconstitution, but both CD4+ and CD8+ T cells require thymic activity for maintenance or regeneration of repertoire diversity. These findings have led in turn to a research emphasis on understanding mechanisms which control thymic function, and new treatments, including vaccine strategies, to treat cancer in the setting of a regenerating immune system. Four models of thymic regulation have been developed; this work has progressed to the developoment of two new project areas of research -- one focused on points of regulation of thymus function and one on introducing agents into clinical trials. The work addressed in this project has also led to efforts in investigating IL-7 effects on the maturation of thymocytes. We have identified IL-7 as a negative regulator of thymopoiesis as well as being essential for thymocyte development. These dual roles are dose dependent and negative regulation at higher concentrations is mediated through control of Notch signaling -- which is central to T/B lineage commitment. Additionally, we have worked to identify genes which might regulate the thymus, and have characterized a gene called Tbata (previously SPATIAL) which is a negative regulator acting within the stromal cell compartment. It appears to exert its effect through control of cell cycle, specifically through regulation of the Nedd8 pathway. Recent results indicate that regulation of cell cycle by Tbata extends beyond Nedd8 and involves p53. The cellular and molecular mechanisms by which androgen signaling blockade and IGF-1 modulate thymus function were characterized and map points of regulation of proliferation to the epithelial cell compartment of the thymus. A new transgenic murine model has been developed to investigate signaling pathways involved in this regulation. This new model involves the ability to deplete the peripheral T cell compartment without ancillary tissue injury. Using the information that a key control point of thymus regulation is the control of thymic epithelial cell proliferation, gene arrays are being carried out at fixed time intervals on isolated cells to identify activated cell pathways of division. In parallel, LC/MS is being used to identify new protein species that may act as ligands for those identified pathways. Three unidentified proteins have been found and are being validated. The role of IL-7 as a possible regulator of thymus function was noted above; its role in peripheral homeostasis has been further investigated by charactreizing IL-7 receptor regulation among T cell subsets. The purpose in all of these studies is to understand the biology of T cell homeostasis in order to develop new approaches to therapy for patients in whom T cell populations are depleted with consequences of impaired immunity. To date, IL-7 has been introduced in humans and a clinical trial with androgen blockade is in progress. The trial with androgen blockage shows early positive results which need to be confirmed as the trial continues. The work with IL-7 receptor modulation has shown a complex pattern of differential signaling regulation among subsets with the apparent effect of favoring the sustaining of primitive naive T cells. This is of special interest because it provides a basis for understanding how a single cytokine such as IL-7 can differentially regulate multiple distinct T cell subsets. Specifically, there is differential regulation between naive CD4 T cells versus recent thymic emigrants, and also between CD4 and CD8 T cells. Differences in signaling distal to the receptor for IL-7 appear to mechanistically account for this differential regulation. In humans, we noted that CD4 recovery was more limited than CD8 recovery following chemotherapy. Reasons for this are not known. We are now addressing the biology of signaling by the two primary homeostatic cytokines in the CD4 versus the CD8 subsets in murine models and have found a new layer of complexity in signaling that remains to be characterized. We have also made the observation that in T cell immune reconstitution reliant on the thymus-independent pathway in humans, that such expansion results in premature aging of the T cells with resultant cellular senescence, a likely contributor to T cell functional impairment following transplant.

急性损失后 T 细胞群重建的生物学特征仍未完全确定。使用小鼠模型，我们首先确定了 T 细胞免疫重建的两条主要途径，即经典的胸腺依赖性途径和第二条胸腺非依赖性途径。然后，我们鉴定了 T 细胞表面标记，通过对重建的 T 细胞群进行表型分析，可以识别产生它们的途径，然后将这些信息应用于患者 T 细胞重建的表征。最初的工作确立了这种方法在年轻人类 T 细胞群再生研究中的适用性。最近的工作验证了该方法的有效性，并确定了成年人在较长时间内两种主要途径中 T 细胞免疫重建的过程。这项工作显示了胸腺在 CD4+ T 细胞定量再生中的重要作用。 CD8+ T 细胞可以通过外周扩张进行数字重建以进行免疫重建，但 CD4+ 和 CD8+ T 细胞都需要胸腺活性来维持或再生库多样性。这些发现反过来导致研究重点放在了解控制胸腺功能的机制，以及在免疫系统再生的情况下治疗癌症的新疗法，包括疫苗策略。已开发出四种胸腺调节模型；这项工作已发展为两个新项目研究领域的发展——一个侧重于胸腺功能的调节点，另一个侧重于将药物引入临床试验。该项目中涉及的工作还导致了研究 IL-7 对胸腺细胞成熟的影响的努力。我们已确定 IL-7 是胸腺生成的负调节因子，并且对于胸腺细胞的发育至关重要。这些双重作用是剂量依赖性的，较高浓度下的负调节是通过控制 Notch 信号传导介导的，而 Notch 信号传导是 T/B 谱系定型的核心。此外，我们还致力于鉴定可能调节胸腺的基因，并鉴定了一种名为 Tbata（以前称为 SPATIAL）的基因，该基因是在基质细胞区室中发挥作用的负调节因子。它似乎通过控制细胞周期发挥作用，特别是通过调节 Nedd8 途径。最近的结果表明，Tbata 对细胞周期的调节超出了 Nedd8 范围，并涉及 p53。雄激素信号传导阻断和 IGF-1 调节胸腺功能的细胞和分子机制得到了表征，并将增殖调节点映射到胸腺的上皮细胞区室。已经开发出一种新的转基因小鼠模型来研究参与这种调节的信号通路。这种新模型能够在不损伤辅助组织的情况下耗尽外周 T 细胞区室。利用胸腺调节的关键控制点是胸腺上皮细胞增殖的控制这一信息，在固定的时间间隔对分离的细胞进行基因阵列，以识别激活的细胞分裂途径。与此同时，LC/MS 也被用来鉴定新的蛋白质种类，这些蛋白质种类可以作为这些已鉴定途径的配体。已经发现并正在验证三种未识别的蛋白质。 IL-7 作为胸腺功能的可能调节剂的作用如上所述；通过表征 T 细胞亚群中 IL-7 受体的调节，进一步研究了其在外周稳态中的作用。所有这些研究的目的是了解 T 细胞稳态的生物学原理，以便为 T 细胞群耗尽而导致免疫力受损的患者开发新的治疗方法。迄今为止，IL-7 已被引入人体，雄激素阻断的临床试验正在进行中。雄激素阻断试验显示了早期的积极结果，需要随着试验的继续而得到证实。 IL-7 受体调节的工作显示了亚群之间差异信号传导调节的复杂模式，具有有利于维持原始幼稚 T 细胞的明显效果。这是特别令人感兴趣的，因为它为理解单一细胞因子（例如 IL-7）如何差异调节多个不同的 T 细胞亚群提供了基础。具体来说，初始 CD4 T 细胞与最近的胸腺移出细胞之间以及 CD4 和 CD8 T 细胞之间也存在差异调节。 IL-7 受体远端信号传导的差异似乎在机制上解释了这种差异调节。在人类中，我们注意到化疗后 CD4 的恢复比 CD8 的恢复更有限。其原因尚不清楚。我们现在正在研究小鼠模型中 CD4 与 CD8 亚群中两种主要稳态细胞因子的信号传导生物学，并发现了信号传导的新一层复杂性，仍有待表征。我们还观察到，在人类依赖于胸腺独立途径的 T 细胞免疫重建中，这种扩增会导致 T 细胞过早衰老，从而导致细胞衰老，这可能是移植后 T 细胞功能损伤的原因之一。