COSTIMULATORY BLOCKADE AND CHIMERISM TOLERANCE

CD 40/CD 28共刺激阻断是一种非常有效的策略， 同种异体移植物存活率。然而，接受这种治疗的患者最终 发生晚期移植排斥反应，表明单独阻断共刺激 不会诱导稳定的移植耐受。相反，协议 诱导高水平的造血嵌合体， 在成年动物中发展强大的供体特异性耐受性。然而，在这方面， 这些方案依赖于使用细胞毒性剂来消耗细胞毒性剂。 接受者的外周免疫系统和/或骨髓来创造“空间” 移植造血干细胞（HSC）。 我们开发了一种新的方案，捐赠者的骨髓 作为骨髓基质的碎片移植到肾包膜下或 接受者的皮下空间。我们观察到这些骨头 骨髓移植物（BG）含有完整的基质微环境， 造血成分植入并填充外周血 血液循环而不需要骨髓减少剂。我们发现，当 在小鼠中，通过完全MHC错配的屏障移植， CD 40/CD 28共刺激阻断和BG可以允许植入 这些骨移植物并诱导对随后供体的稳定耐受 特殊皮肤移植 该项目的中心假设是， 阻断/BG方案可持续产生骨植入 移植物、稳定造血嵌合体和稳定移植耐受 通过选择性删除同种异体反应性T细胞。在这个项目中，我们将 严格探索骨髓移植的障碍，优化 克服这些障碍的战略，并研究 这种方法在小鼠中诱导的耐受性。然后我们将这个 对临床前恒河猴肾移植研究的认识 模型，目的是产生一个耐受诱导方案， 适用于临床移植试验。

CD40/CD28 costimulation blockade is a very effective strategy to prolong allograft survival. However, recipients receiving this therapy ultimately undergo late graft rejection, suggesting that costimulation blockade alone will not induce stable transplantation tolerance. In contrast, protocols that induce high levels of hematopoietic chimerism result in the development of robust donor-specific tolerance in adult animals. However, these protocols rely on the use of cytotoxic agents to deplete the recipient's peripheral immune system and or bone marrow to create "space" for the transplanted hematopoietic stem cells (HSC's). We have developed a novel protocol in which the donor's bone marrow is grafted as fragments of bone marrow matrix under the kidney capsule or in the subcutaneous space of the recipient. We have observed that these bone marrow grafts (BG) which contain an intact microenvironment of stromal and hematopoietic elements engraft and populate the peripheral blood circulation without the need for myelo-reductive agents. We find that when transplanted across fully MHC mismatched barriers in mice, the combination of CD40/CD28 co-stimulation blockade and BG can permit engraftment of these bone grafts and induce stable tolerance to a subsequent donor specific skin graft. The central hypothesis of this project is that the costimulation blockade/BG protocol can consistently produce engraftment of the bone graft, stable hematopoietic chimerism and stable transplantation tolerance via selective deletion of alloreactive T cells. In this project we will rigorously explore barriers to bone marrow engraftment, optimize strategies to overcome these barriers, and study the mechanisms of tolerance induced by this approach in mice. We will then integrate this knowledge into our studies in the pre-clinical Rhesus renal allograft model, with the goal of producing a tolerance induction protocol that is suitable for testing in clinical transplantation.