Defining the Earliest Stages of Lymphoid Commitment in Human Bone Marrow

描述（由申请人提供）：大量的报告继续细化小鼠淋巴系统的分化阶段。然而，关于人类淋巴细胞分化的早期阶段所知甚少，存在的少数报告大多使用脐带血。本研究计划中的研究将通过鉴定和表征人类骨髓中能够产生T细胞的最原始淋巴样祖细胞，解决我们对成人淋巴系统知识的关键空白。这些研究的总体目标是鉴定成人骨髓中具有最大T细胞生产能力的淋巴样祖细胞。我们已经在人骨髓中发现了一个祖细胞群，表达高水平的归巢分子l -选择素（CD62L），并在体外具有强大的淋巴细胞潜能。我们假设这种CD34+ CD10- cd62l++（“CD10-”）淋巴细胞限制性祖细胞群标志着人类造血干细胞参与淋巴细胞分化途径的第一阶段。此外，我们提出CD10-群体是一个更原始的前体，具有优于先前描述的人骨髓中的CD34+ CD10+（“CD10+”）LP群体的T淋巴细胞潜能。Aim 1的研究通过定义CD10-和CD10+ LPs的分子特征来解决人类淋巴细胞承诺的生物学问题。这些研究根据两个LP群体的基因表达谱确定了它们之间的谱系关系，无论是在全球范围内还是在特定情况下，都使用了已知对淋巴细胞发育至关重要的基因。Aim 2中的研究通过确定CD10-和CD10+ LPs返回和重建胸腺的能力，以及通过体外测定和体内异种移植模型定量来自每种群体的T细胞的相对功能输出来解决临床相关性。这些知识对于淋巴细胞分化和胸腺重建的诊断和治疗进展的发展是必不可少的。

DESCRIPTION (provided by applicant): A large number of reports continue to refine the differentiation stages of murine lymphopoiesis. However very little is known about the earliest stages of human lymphoid differentiation, those few reports that exist have mostly used umbilical cord blood. The studies in this research proposal will address a critical gap in our knowledge of adult human lymphopoiesis, through the identification and characterization of the most primitive lymphoid progenitors in the human bone marrow able to generate T cells. The overall goal of these studies is to identify the lymphoid progenitors in adult human bone marrow with maximum T cell production capacity. We have identified a progenitor population in human bone marrow that expresses high levels of the homing molecule L-selectin (CD62L) and possesses robust lymphoid potential in vitro. We hypothesize that this CD34+ CD10- CD62L++ ("CD10-") lymphoid-restricted progenitor population marks the first stage of commitment by human hematopoietic stem cells to the lymphoid differentiation pathway. Further, we propose that the CD10- population is a more primitive precursor with superior T lymphoid potential to the previously described CD34+ CD10+ ("CD10+") LP population in human bone marrow. The studies in Aim 1 address the biology of human lymphoid commitment by defining the molecular characteristics of the CD10- and CD10+ LPs. These studies define the lineage relationship between the two LP populations based on their gene expression profiles, both globally and specifically using genes that are known to be critical to lymphoid development. The studies in Aim 2 address clinical relevance by determining the ability of the CD10- and CD10+ LPs to home and reconstitute the thymus and by quantifying the relative functional output of T cells from each population using in vitro assays and in vivo using a xenogeneic transplant model. This knowledge is essential for the development of diagnostic and therapeutic advances toward the process of lymphoid differentiation and thymic reconstitution. PUBLIC HEALTH RELEVANCE: This proposal will examine how the immune system develops from stem cells in the bone marrow of humans during adult life. These studies will increase our knowledge of how the cells of the immune system can be isolated and manipulated in order to improve outcomes by decreasing infections after hematopoietic stem cell transplant.