Immune privilege of the hematopoieitic stem cell niche

项目摘要 虽然干细胞龛作为调节干细胞功能的位点已经被广泛研究， 小生境的免疫学属性仍然在很大程度上未被探索。有趣的是，睾丸和 胎盘，干细胞的居住器官，已知是干细胞的免疫避难所，称为 免疫特权（IP）网站。IP部位的严格免疫抑制由移植的存活证明。 同种异体或异种移植物，而没有任何外源性免疫抑制治疗。知之甚少 组织定向干细胞龛是否是IP位点，如睾丸和胎盘。总体假设 造血干细胞和祖细胞（HSPC）是最具特征的干细胞小生境之一， 在骨髓（BM）中，是IP部位。在小生境中的IP可以防止移植的同种异体（allo-） HSPCs，并保护恶性干细胞免受免疫攻击。因此，IP可能是一个新的原则， 提供了几种临床设置的机械基础。我们以前的研究表明，HSPC niche是一个IP地址。高灵敏度的体内显微镜（IVM）能够检测持续存在的allo-HSPC， 免疫活性小鼠，而没有免疫抑制治疗超过60天。FoxP3+ 调节性T细胞（TCFs）经常与HSPC形成簇。全身性Treg耗竭导致allo-HSPC 排斥反应这些数据表明，TMF赋予了利基知识产权。我们进一步观察到MLL-AF 9白血病 干细胞（LSC）归巢于BM T细胞，这是IP位点的标志，表明IP屏蔽了LSC。开发一个 新的治疗方法来操纵IP以促进allo-HSPC植入或根除BM恶性肿瘤，这是重要的 以获得对知识产权的进一步机械见解。在目标1中，我们将研究BM TGFs、间充质细胞和间充质细胞的作用。 细胞和CD 11b + Gr 1+骨髓细胞在IP维持和无免疫的allo-HSPC持续性中的作用 镇压为了实现这一目标，我们将采用以下四种方法： 由于TCR 4的条件性缺失导致的BM; B）TCR 4中CD 39的条件性缺失; c）TCR 4中CD 39的条件性缺失 在lepr+间充质细胞中缺失CXCL 12;和d）通过抗Gr 1抗体耗竭CD 11b + Gr 1+细胞 治疗我们将确定这些方法是否会导致移植的allo-HSPCs的排斥反应， 免疫抑制，通过使用体内显微镜、流式细胞术和二次移植测定。在 目的2，我们将测试IP是否保护LSC免受免疫，并进一步阐明BM TGFAP的作用， 间充质细胞和CD 11b + Gr 1+髓样细胞使LSC逃避免疫。我们将确定 MLL-AF 9白血病的排斥是否由a）由于TcR中CXCR 4缺失而导致的BM TcR缺乏，B） CD 39抑制剂治疗，c）麻风病+间充质细胞中的CXCL 12缺失，和d）骨髓细胞耗竭。 成功的研究将创造一个新的范式，即HSPC生态位是两者的免疫避难所。 异基因HSPC和恶性干细胞。此外，这些机制和系统的分析知识产权将 为allo-HSPC移植和恶性肿瘤建立新的治疗策略。

Project Abstract Although the stem cell niche has been extensively studied as a site that regulates stem cell functions, immunological attributes of the niche have remained largely unexplored. Interestingly, the testis and the placenta, organs for residence of stem cells, are known to be immunological sanctuaries for stem cells, termed immune privileged (IP) sites. Rigorous immune suppression in IP sites is evidenced by survival of transplanted allogeneic or xenogeneic grafts without any exogenous immune suppressive therapy. Little is known about whether tissue-committed stem cell niches are IP sites, like the testis and the placenta. The overall hypothesis is that one of the best-characterized stem cell niches, the hematopoietic stem and progenitor cell (HSPC) niche in the bone marrow (BM), is an IP site. IP in the niche may prevent rejection of transplanted allogeneic (allo-) HSPCs, and shield malignant stem cells from immune attack. Therefore, IP may be a novel principle that provides a mechanistic underpinning of several clinical settings. Our previous study indicates that the HSPC niche is an IP site. Highly sensitive in vivo microscopy (IVM) enabled detection of allo-HSPCs persisting in immune competent mice without immune suppressive therapy for more than 60 days. Moreover, FoxP3+ regulatory T cells (Tregs) frequently formed clusters with HSPCs. Systemic Treg depletion led to allo-HSPC rejection. The data suggest that Tregs endow the niche with IP. We further observed that MLL-AF9 leukemia stem cells (LSCs) home to BM Tregs, a hallmark of IP sites, suggesting that IP shields LSCs. To develop a new therapy to manipulate IP to promote allo-HSPC engraftment or eradicate BM malignancies, it is important to obtain further mechanistic insights into IP. In Aim 1, we will investigate the role of BM Tregs, mesenchymal cells, and CD11b+Gr1+ myeloid cells in IP maintenance and allo-HSPC persistence without immune suppression. To achieve this goal, we will employ the following four approaches: a) inhibition of Treg homing to the BM due to conditional deletion of CXCR4 in Tregs; b) conditional deletion of CD39 in Tregs; c) conditional deletion of CXCL12 in lepr+ mesenchymal cells; and d) CD11b+Gr1+ cell depletion by anti-Gr1 antibody treatment. We will determine whether these approaches lead to rejection of allo-HSPCs transplanted without immune suppression, by using in vivo microscopy, flow cytometry, and secondary transplantation assay. In Aim 2, we will test whether IP shields LSCs from immunity, and further elucidate the role of BM Tregs, mesenchymal cells, and CD11b+Gr1+ myeloid cells in allowing LSCs to evade immunity. We will determine whether rejection of MLL-AF9 leukemia is induced by a) lack of BM Tregs due to CXCR4 deletion in Tregs, b) CD39 inhibitor treatment, c) CXCL12 deletion in lepr+ mesenchymal cells, and d) myeloid cell depletion. Successful studies will create a novel paradigm that the HSPC niche is an immunological sanctuary for both allo-HSPCs and malignant stem cells. Furthermore, these mechanistic and systematic analyses of IP will establish novel therapeutic strategies for allo-HSPC transplantation and malignancies.