MIXED CHIMERISM AND TOLERANCE IN CYNOMOLGUS MONKEYS

诱导特异性移植耐受，可以消除长期免疫抑制药物的需要和长期存在的慢性排斥问题，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，混合淋巴细胞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。基于这些小鼠研究，我们成功地开发了一种非清髓性制备方案，允许在MHC不相合的食蟹猴中诱导混合嵌合体和肾移植耐受，而不是GvHD。然而，要将这种方案应用到临床环境中，需要进行几次修改。因此，这项建议的主要目标是实现一致的耐受性，进一步降低预备性方案的发病率，并将其应用于身体器官移植。具体地说，我们将：1)评估将共刺激阻断(与抗CD40L单抗和/或CTLA4-Ig)添加到准备方案中；2)尝试通过利用高剂量动员的外周血干细胞(PBSC)诱导混合嵌合体来最大限度地减少准备方案的辐射需求；以及3)修改准备方案以提高其在身体供体移植中的适用性。此外，我们将调查和比较每种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。这些分析应该为将这种方法推广到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 use to the transplantation of cadaveric organs. Specifically, we will: 1) evaluate the addition of costimulatory blockade (with anti-CD40L monoclonal antibody and/or CTLA4-Ig) to the preparative regimen; 2) attempt to minimize the radiation requirements of the preparative regimen by utilizing high-dose mobilized peripheral blood stem cells (PBSC) for the induction of mixed chimerism; and 3) modify the preparative regimen to improve its applicability to cadaver-donor transplantation in humans. 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.