TOLERANCE IN PRIMATES--THYMIC IMPLANTATION OF STEM CELL

这项提议的目的是在灵长类动物身上测试一种新的治疗方法 对实体器官移植产生耐受性：纯净供体的植入 CD34骨髓细胞进入受体胸腺。在试点研究中， 研究人员已经实现了：1)6/6的造血微嵌合体 接受或不接受当前三联药物免疫抑制的幼年狒狒； 2)供体皮肤移植物与第三方皮肤移植物存活时间的特异性延长； (3)16个月时无移植物抗宿主病。这些 实验验证了将该方法扩展到心脏的可行性。 幼年狒狒模型的移植作为临床前试验。 解决了以下问题：1)胸腺内植入 CD34骨髓细胞延长心脏移植物存活时间？2)什么 造血微嵌合体与耐受性之间的关系 移植到同种异体心脏？3)是胸腺内植入干细胞吗？ 比外周输液更有效吗？4)有什么效果 目前的药物治疗对植入性和耐受性的影响？5)什么是 干细胞给药相对于心脏的最佳时机 移植？6)需要多大剂量的细胞？7)DR组分 移植是必要的吗？细胞免疫的测量有改变吗？ 将CD34细胞植入幼年狒狒体内进行实验。 经小开胸术和颈部异位胸腺切除术 便于活组织检查的心脏移植物。免疫抑制包括 目前临床应用的三联免疫抑制方案， 没有骨髓清扫或宿主T细胞耗尽，也没有免疫抑制。 仅1×10/6细胞的剂量就导致了造血细胞微嵌合体 在所有收件人中。微嵌合体的持久性。组织学 浸润性白细胞亚群与冠脉微血管的定量 黏附分子的表达将与对照组进行比较。的水平 实现了嵌合体，它的持久性，干细胞后代的表型， 对供体导向的CTLp的影响，以及对胸腺的依赖 评估过了。 心脏手术期间CD34骨髓细胞在胸腺内的植入 移植程序可能提供一种简单、安全的生产方法 对移植物和微嵌合体的耐受性。这种方法论显然具有 实体器官移植的即刻临床应用。 根据嵌合体水平的不同， 将同种异基因干细胞移植到婴儿体内而不产生免疫抑制 也可能对遗传缺陷的治疗有影响。 疾病。

The aim of this proposal is to test in primates a new method for producing tolerance to solid organ grafts: implantation of purified donor CD34+ marrow cells into the recipient thymus. In pilot studies, the investigators have achieved: 1) hematopoietic microchimerism in 6/6 juvenile baboons with or without current triple drug immunosuppression; 2) specific prolongation of donor versus third party skin graft survival; and 3) absence of graft versus host disease at 16 months. These experiments test the feasibility of extending this approach to cardiac transplantation in a juvenile baboon model as a pre-clinical trial. The following questions are addressed: 1) Does intrathymic implantation of CD34+ marrow cells prolong survival of cardiac allografts? 2) What is the relationship between hematopoietic microchimerism and tolerance to a cardiac allograft? 3) Is intrathymic implantation of stem cells more effective than peripheral infusion? 4) What are the effects of current drug therapy on engraftment and tolerance? 5) What is the optimal timing of stem cell administration relative to cardiac transplantation? 6) What dose of cells is needed? 7) Are DR+ fractions necessary for engraftment? 8) Are measures of cellular immunity altered? Experiments are performed in juvenile baboons, implanting CD34+ cells in the thymus through a small thoracotomy and using a cervical heterotopic cardiac graft which facilitates biopsies. Immunosuppression consists of the tripe drug immunosuppressive regimen in current clinical practice, without myeloablation or host T cell depletion, or no immunosuppression. A dose of only 1x 10/6 cells has resulted in hematopoietic microchimerism in all recipients. Persistence of microchimerism. Histologic quantitation of infiltrating leukocyte subsets and coronary microvascular adhesion molecule expression will be compared to controls. The level of chimerism achieved, its persistence, the phenotype of stem cell progeny, effect on donor-directed CTLp, and the dependence on the thymus will be assessed. Implantation of CD34+ marrow cells in the thymus during a cardiac transplant procedure may provide a simple, safe method of producing tolerance to the graft and microchimerism. This methodology has obvious immediate clinical applications in solid organ transplantation. Depending on the level of chimerism achieved, the potential for introducing allogenic stem cells into an infant without immunosuppression might also have implications for the treatment of genetic deficiency diseases.