TOLERANCE TO VASCULARIZED ALLOGRAFTS IN MINISWINE

描述(申请人提供)：近交系小型猪为移植免疫和耐受研究提供了一种独特的临床前模型。我们先前已经证明，在这个模型中，经过短疗程的钙调神经磷酸酶抑制剂，可以实现对MHC-L不匹配的同种异体肾移植的强大耐受性。由于与中枢耐受不同，在该系统中诱导耐受不涉及T细胞消融，而且由于T细胞是长期存活的，因此该建议的中心假设是，这种形式的耐受涉及一种持续的机制，下调T细胞的反应性。在上一个项目期间，我们的近亲繁殖计划已经培育出近亲繁殖系数为94%的亚系，首次允许在大型动物模型中通过领养转移来研究耐受性的机制。我们使用这些动物的数据表明，对I类错配肾移植的耐受涉及调节性T细胞(T-reg)，这些T细胞可以从长期耐受的肾脏中分离出来，也可以在DST后动员到外周。我们还观察到，在移植物移除后，耐受性至少持续3个月，在此期间，供体I类多肽免疫，而不是通过排斥供体皮肤移植物，取消了耐受状态。最后，我们发现，用DST和白细胞分离术治疗耐受动物，成功地将它们的耐受转移到领养家庭，也会导致耐受状态的丧失。总而言之，这些数据表明，耐受性依赖于同种异体反应和调节之间的平衡，这是通过移植物和受体免疫系统之间可定义的细胞相互作用来维持的。为了验证这些假设，我们将1)确定负责通过过继转移转移耐受性的细胞群体的性质；2)研究抗原呈递途径决定耐受性维持与丧失的机制；3)检查同种异体反应性和调节之间的平衡，这决定了第二次移植到耐受者的命运。希望在这个大型动物模型中对诱导和维持同种异体移植耐受的机制的理解将有助于开发适当的临床方案来诱导对同种异体器官移植的特异性耐受。

DESCRIPTION (provided by applicant): Inbred miniature swine provide a unique preclinical model for the study of transplantation immunity and tolerance. We have previously demonstrated that robust tolerance to MHC class l-mismatched renal allografts can be achieved following a short course of calcineurin inhibitors in this model. Since, unlike central tolerance, the induction of tolerance in this system does not involve T cell ablation, and since T cells are long-lived, the central hypothesis of this proposal is that this form of tolerance involves a continuing mechanism for down-regulation of T cell reactivity. During the last project period, our inbreeding program has produced a subline with >94% coefficient of inbreeding, permitting investigation of the mechanism of tolerance by adoptive transfer for the first time in a large animal model. Our data using these animals indicate that tolerance to class I mismatched renal allografts involves regulatory T cells (T-reg) that can be isolated from the long-term tolerated kidney and can also be mobilized in the periphery following DST. We have also observed that tolerance persists for at least 3-months after removal of the graft, and that during this period, immunization by donor class I peptides, but not by rejection of donor skin grafts, abrogates the tolerant state. Finally, we have found that the treatment of tolerant animals with DST and leukapheresis, required for successful adoptive transfer of their tolerance, also leads to loss of the tolerant state. Collectively, these data suggest that tolerance relies on a balance between alloreactivity and regulation, which is maintained via definable cellular interactions between the graft and the recipient's immune system. To test these hypotheses, we will 1) Determine the nature of the cell populations responsible for transfer of tolerance by adoptive transfer; 2) Study the mechanism by which the pathway of antigen presentation determines maintenance vs. loss of tolerance; and 3) Examine the balance between alloreactivity and regulation that determines the fate of a second transplant into a tolerant recipient. It is hoped that an understanding of the mechanisms by which allograft tolerance is induced and maintained in this large-animal model will permit development of appropriate clinical protocols for induction of specific tolerance to organ allografts.