Immune Reconstitution

急性丧失后T细胞群重建的生物学特征仍不完全。使用小鼠模型，我们首先确定了T细胞免疫重建的两个主要途径，经典的，胸腺依赖性途径，和第二个，胸腺非依赖性途径。然后，我们确定了T细胞表面标志物，其允许通过对重建的T细胞群体进行表型分析来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。这项工作显示了胸腺在定量再生CD 4 + T细胞中的重要作用。CD 8 + T细胞可以通过外周扩增在数量上重建以用于免疫重建，但CD 4+和CD 8 + T细胞都需要胸腺活性以维持或再生库多样性。这些发现反过来又导致研究重点放在理解控制胸腺功能的机制上，以及在再生免疫系统的背景下治疗癌症的新疗法。这项工作已发展到两个新的研究项目领域-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。在这个项目中解决的工作也导致了在研究IL-7对胸腺细胞成熟的影响的努力。我们已经确定了IL-7作为胸腺生成的负调节因子以及对于胸腺细胞发育是必需的。这些双重作用是剂量依赖性的，并且在更高浓度下的负调节是通过Notch信号传导的控制介导的，Notch信号传导是T/B谱系定型的中心。在高剂量下，IL-7有利于B细胞发育，因此使胸腺向B细胞生成器官转变。此外，我们还努力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，该基因是基质细胞室中的负调节因子。它似乎通过控制细胞周期，特别是通过调节Nedd 8途径发挥其作用。最近的研究结果表明，Tbata对细胞周期的调节超出了Nedd 8，并涉及p53。这是由于Tbata编码的蛋白质参与了控制基因表达的大型多蛋白质复合物。有趣的是，这可能反映在雌性小鼠与雄性小鼠胸腺生成的差异上。从多个实验中可以清楚地看出这种差异，其机制正在研究中。实验正在进行中，以确定可能具有临床应用性的Tbata功能阻断剂。IL-7作为胸腺功能的可能调节剂的作用如上所述;其在外周稳态中的作用已通过表征T细胞亚群中的IL-7受体调节而进一步研究。IL-7受体调节的工作显示了亚群之间差异信号调节的复杂模式，具有有利于维持原始幼稚T细胞的明显作用。这是特别感兴趣的，因为它提供了理解单个细胞因子如IL-7如何差异调节多个不同的T细胞亚群的基础。具体地，在初始CD 4 T细胞和记忆CD 4 T细胞之间存在差异调节。IL-7受体远端信号传导的差异似乎在机械上解释了这种差异调节。我们现在正在解决由两个主要的稳态细胞因子在小鼠模型中的CD 8幼稚与CD 8记忆亚群的信号转导的生物学，并再次发现在T细胞受体周转水平的差异。这些结果现已公布。我们还观察到，在依赖于人类胸腺非依赖性途径的T细胞免疫重建中，这种扩增导致T细胞的过早老化，从而导致细胞衰老，这可能是移植后多年T细胞功能受损的原因。研究小鼠模型中的干细胞区室，我们发现FLT 3配体通过与CXCR 4和骨髓小生境的相互作用调节胸腺前体细胞和造血干细胞。最后，一系列的实验，使用氘代葡萄糖，以评估T细胞亚群的动力学在慢性GVHD的发病机制，在小鼠模型中产生的信息，这些子集，并演变成成功的图像在该疾病中的细胞迅速增殖的努力。这项合作工作已经发展到其他快速增殖细胞，即肿瘤细胞的成像。该成像具有足够的灵敏度和特异性，具有临床意义。它还可以在通过基于增殖活性的同位素的选择性摄取治疗疾病中具有治疗应用。

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. 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 led in turn to a research emphasis on understanding mechanisms which control thymic function, and new treatments to treat cancer in the setting of a regenerating immune system. This work has progressed to the development 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. At high doses, IL-7 favors B cell development and so turns the thymus towards a B cell-poietic organ. 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. This is due to involvement of the protein encoded by Tbata in a large multi-protein complex which controls gene expression. Interestingly, this may be reflected in differences of thymopiesis in female versus male mice. The difference is now clear from multiple experiments, and the mechanism is under investigation. Experiments are in progress to identify blockers of Tbata function that might have clincial applicability. 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 characterizing IL-7 receptor regulation among T cell subsets. 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 and memory CD4 T cells. Differences in signaling distal to the receptor for IL-7 appear to mechanistically account for this differential regulation. We are now addressing the biology of signaling by the two primary homeostatic cytokines in the CD8 naive versus CD8 memory subsets in murine models and have found again differences at the level of T cell receptor turnover. These results are now published. 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 for years following transplant. Investigating the stem cell compartment in murine models, we showed that FLT3 ligand regulates thymic precursor cells and hematopoietic stem cells through interactions with CXCR4 and the marrow niche. Finally, a series of experiments using deuterated glucose to assess T cell subsets kinetics in the pathogenesis of chronic GVHD in murine models yielded information on such subsets and evolved into efforts to successfully image rapidly proliferating cells in that disease. This collaborative work has progressed to imaging of other rapidly proliferating cells, namely neoplastic cells. This imaging has sufficient sensitivity and specificity to be of clinical interest. It also may have therapeutic application in the treatment of disease by selective uptake of isotope based on proliferative activity.