Immune Reconstitution

在过去，T细胞群在急性损失后的重建生物学还没有完全被描述。通过小鼠模型，我们首先确定了T细胞免疫重建的两种主要途径，一种是经典的胸腺依赖途径，另一种是胸腺独立途径。然后，我们确定了T细胞表面标记物，通过重组T细胞群的表型分析，可以识别产生它们的途径，然后将这些信息应用于患者T细胞重组的表征。最初的工作确定了这种方法在人类T细胞群体再生研究中的适用性。最近的工作验证了该方法的有效性，并确定了成人中T细胞免疫重建的两个主要途径随时间的变化过程。这项工作也显示了胸腺在定量再生CD4+ T细胞中的重要作用。CD8+ T细胞更强烈地依赖外周扩张来进行免疫重建。CD4+和CD8+ T细胞都需要胸腺活性来维持或产生库多样性。这些发现导致研究重点转向了解控制胸腺功能的机制，以及包括疫苗策略在内的新治疗方法，以在再生免疫系统的背景下治疗癌症。目前已发展出四种胸腺调节模型；这项工作已经发展到两个新的研究项目领域——一个专注于胸腺功能的调节，另一个专注于将药物引入临床试验。在这个项目中解决的工作也导致了研究IL-7对胸腺细胞成熟的影响的努力。我们已经确定IL-7是胸腺生成的负调节因子，也是胸腺细胞发育所必需的。这些双重作用是剂量依赖性的，高浓度的负调节是通过控制Notch信号传导介导的，这是T/B谱系承诺的核心。此外，我们已经确定了可能调节胸腺的基因，并确定了一种名为Tbata（以前称为SPATIAL）的基因，这是一种在基质细胞内起作用的负调节作用。它似乎通过控制细胞周期，特别是通过调节Nedd8通路发挥作用。研究了雄激素信号阻断和IGF-1调节胸腺功能的细胞和分子机制，并绘制了胸腺上皮细胞区室增殖调控点。目前正在开发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。这种新模型涉及到在没有辅助组织损伤的情况下消耗外周T细胞室的能力。利用胸腺调控的一个关键控制点是胸腺上皮细胞增殖的控制这一信息，在离体细胞上以固定的时间间隔进行基因阵列，以鉴定活化的细胞分裂途径。与此同时，LC/MS也被用于鉴定可能作为这些已鉴定途径的配体的新蛋白质物种。

The biology of reconstitution of T cell populations following acute loss has, in the past, been 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. Recent work verified validity of the approach and established the course of T cell immune reconstitution in adult humans over time for each of the two primary pathways. This work also showed an essential role for the thymus in regenerating CD4+ T cells quantitatively. CD8+ T cells depend more strongly on peripheral expansion for immune reconstitution. Both CD4+ and CD8+ T cells require thymic activity for maintenance or generation 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. 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 is being 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.