MIXED CHIMERISM AND TOLERANCE IN CYNOMOLGUS MONKEYS

诱导特异性移植耐受，这可能消除对长期免疫抑制药物的需要和慢性排斥反应的持续问题，仍然是临床器官移植的主要目标。本实验室以前的研究表明，混合淋巴造血嵌合体的建立为诱导小鼠跨越主要组织相容性障碍的长期移植耐受提供了一种有效的手段。基于这些鼠研究，我们成功地开发了非清髓性制备方案，其允许在MHC错配食蟹猴中骨髓移植后诱导混合嵌合体和肾同种异体移植物耐受，而没有GVHD。然而，为了将该方案应用于临床环境，需要进行几次修改。因此，本建议的主要目标是实现一致的耐受性，以进一步降低发病率的准备方案，并扩大其临床应用。具体而言，我们将：1）评估共刺激阻断的添加（用抗-CD 40配体单克隆抗体和/或CTLA 4-IG）; 2）通过利用高剂量动员的外周血干细胞（PBSC）移植或使用环磷酰胺，尝试最小化或消除准备方案的辐射要求;和3）修改制备方案以改善其对尸体供体移植和具有良好肾功能的活体供体移植的受体的临床适用性，但目前不能耐受标准免疫抑制的患者。此外，我们将研究和比较这些非清髓性方案诱导耐受的潜在机制，特别强调区分中枢和外周机制。这些分析将为临床同种异体移植提供有价值的信息。

The induction of specific transplantation tolerance, which might eliminate both the need for long-term immunosuppressive medications and the persistent problem of chronic rejection, remains a major goal of clinical organ transplantation. Previous studies from our laboratory have demonstrated that the establishment of mixed lymphohematopoietic chimerism provides an effective means for the induction of long-term transplantation tolerance across major histocompatibility barriers in mice. Based on these murine studies, we successfully developed a non- myeloablative preparative regimen that permits the induction of mixed chimerism and renal allograft tolerance following bone marrow transplantation in MHC-mismatched cynomolgus monkeys, without GVHD. However, to apply this regimen to a clinical setting, several modifications will be necessary. Therefore, the major goals of this proposal are to achieve consistent tolerance, to reduce further the morbidity of the preparative regimen, and to extend its clinical application. Specifically, we will: 1) evaluate the addition of costimulatory blockade (with anti-CD40 ligand monoclonal antibody and/or CTLA4-Ig); 2) Attempt to minimize or remove the radiation requirements of the preparative regimen by either utilizing high-dose mobilized peripheral blood stem cell (PBSC) transplantation or the use of cyclophosphamide; and 3) modify the preparative regimen to improve its clinical applicability to cadaver-donor transplantation and to recipients of living donor transplants with good renal function, but who are currently not tolerating standard immunosuppression. In addition, we will investigate and compare the underlying mechanism of tolerance induced by each of these non-myeloablative regimens, with particular emphasis on distinguishing central from peripheral mechanisms. These analyses should provide valuable information for extending this approach to clinical allotransplantation.