Immune Reconstitution

在过去，T细胞群在急性丧失后重建的生物学特征并不完全。利用小鼠模型，我们首先确定了T细胞免疫重建的两条主要途径，经典的胸腺依赖途径和第二条胸腺非依赖途径。然后，我们确定了T细胞表面标志物，通过对重组的T细胞群体进行表型鉴定，确定了导致它们的途径，然后将这些信息应用于患者T细胞重建的特征。最初的工作确立了这种方法在研究人类T细胞群体再生方面的适用性。最近的工作验证了这种方法的有效性，并建立了随着时间的推移，这两条主要途径中的每一条在成人人类中的T细胞免疫重建过程。这项工作也显示了胸腺在数量上再生CD4T细胞的重要作用。CD8T细胞更依赖于外周扩张进行免疫重建。CD4和CD8T细胞都需要胸腺活动来维持或产生谱系的多样性。这些发现反过来又导致了一项研究重点，即了解控制胸腺功能的机制，以及在再生免疫系统的背景下治疗癌症的新疗法，包括疫苗策略。已经开发了四种胸腺调节模型；这项工作已经发展成两个新的研究项目领域--一个集中在胸腺功能的调节点上，另一个集中在将药物引入临床试验中。该项目所涉及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是胸腺生成的负性调节因子，也是胸腺细胞发育所必需的。这些双重作用是剂量依赖的，在较高浓度下的负调节是通过控制Notch信号介导的--Notch信号是T/B谱系承诺的核心。此外，我们还努力识别可能调节胸腺的基因，并鉴定了一种名为Tbata(以前是空间的)的基因，它是一种在基质细胞隔间发挥作用的负调控基因。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。对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进行了研究，并将增殖调节点定位于胸腺上皮细胞室。一种新的转基因小鼠模型正在开发中，以研究参与这一调控的信号通路。这一新模型涉及到在不损伤辅助组织的情况下耗尽外周T细胞隔间的能力。利用胸腺调节的一个关键控制点是控制胸腺上皮细胞增殖的信息，对分离的细胞进行固定时间间隔的基因阵列，以确定激活的细胞分裂途径。同时，LC/MS正被用于识别新的蛋白质物种，这些蛋白质物种可能作为这些已识别途径的配体。

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.