TOLERANCE IN PRIMATES--THYMIC IMPLANTATION OF STEM CELL

这项提议的目的是在灵长类动物中测试一种新的方法， 产生对实体器官移植物的耐受：纯化供体的植入 CD 34+骨髓细胞进入受体胸腺。 在试点研究中， 研究者已经获得：1）6/6的造血微嵌合体 有或无当前三联药物免疫抑制的幼年狒狒; 2)供体与第三方皮肤移植物存活的特异性延长; 3）16个月时无移植物抗宿主病。 这些 实验测试了将这种方法扩展到心脏的可行性， 在幼年狒狒模型中移植作为临床前试验。 以下问题得到解决：1）胸腺内植入是否 CD 34+骨髓细胞延长心脏移植物的存活时间？ 2)什么 造血微嵌合体与免疫耐受的关系 心脏移植手术吗 3)是胸腺内植入干细胞 比外周输液更有效吗 4)有什么影响 目前的药物治疗对移植和耐受性的影响？ 5)是什么 干细胞给药的最佳时间相对于心脏 移植？ 6)需要多少剂量的细胞？ 7)DR+分数 是否需要移植？ 8)细胞免疫指标是否改变？ 实验在幼年狒狒中进行，将CD 34+细胞植入 胸腺通过一个小的开胸和使用颈部异位 便于活检的心脏移植物。 免疫抑制包括 目前临床实践中的三联药物免疫抑制方案， 没有骨髓消融或宿主T细胞耗竭，或没有免疫抑制。 仅1x 10/6细胞的剂量导致造血微嵌合体 在所有的收件人。 微嵌合体的持续存在。 组织学 定量浸润白细胞亚群和冠状动脉微血管 将粘附分子表达与对照进行比较。 水平 嵌合体的实现，其持久性，干细胞后代的表型， 对供体导向的CTLp的影响，以及对胸腺的依赖性将被 评估。 CD 34+骨髓细胞在心脏移植中的胸腺移植 移植手术可能提供一种简单、安全的方法， 对移植物和微嵌合体的耐受性。 这种方法具有明显的 在实体器官移植中的直接临床应用。 根据所达到的嵌合体水平， 在没有免疫抑制的情况下将同种异体干细胞引入婴儿体内 也可能对遗传缺陷的治疗产生影响 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.