Tolerance Induction to Islet Transplants

描述（由申请人提供）：该提案的重点是开发一种新的“调节”方法，该方法将取代骨髓毒性药物，以在NOD小鼠中建立嵌合体。我们将诱导免疫偏离，以促进宿主对移植物的低反应性，从而使造血干细胞（HSC）有机会移植，并建立随后的自我永存缺失耐受胰岛同种异体移植物。我们最近在小鼠模型中的研究表明，HSC移植预处理的主要作用是抑制宿主与移植物的同种异体反应性，而不是在受体的骨髓室中准备空的壁龛。这一观察结果表明，可以取代骨髓毒性剂与抗原特异性的方法，以诱导宿主与移植物低反应性或无反应性的HSC移植的时间。随着T细胞活化的机制被确定，抑制这种同种异体反应性的高度特异性方法已经出现。在AIM I.我们将通过接受者的免疫偏差建立嵌合体。我们将免疫调节受体：（a）靶向宿主微环境中的同种异体反应性细胞;（B）诱导同种异体反应性宿主细胞的无反应性和/或抗原特异性凋亡;（c）通过产生调节性T细胞（Treg），并开发一种新的非清髓性预处理方案，以诱导对HSC和胰岛同种异体移植物的抗原特异性低反应性。基于细胞的治疗在诱导移植耐受方面具有巨大的潜力。最令人感兴趣的是骨髓来源的树突状细胞（DC）的新亚群，最近已被证明是在某些情况下，在体外潜在的耐受性。我们是第一个证明前体浆细胞样DC（p-preDC）的体内移植增强作用。利用这一发现在体内和其潜力，以减少需要骨髓毒性条件尚未进行测试。造血生长因子也已用于通过产生p-preDC或其它耐受促进细胞（移植物促进细胞{FC}）（其进而产生Treg）来驱动对致耐受性辅助性T细胞2（Th 2）表型的免疫应答。在AIM II中，我们将使用造血生长因子对供体进行移植前免疫调节，以在HSC同种异体移植物中产生耐受性细胞。我们将使用这些因子和它们产生的细胞来调节体内供体骨髓接种物的耐受性，以使免疫环境有利于移植物的接受，增强骨髓嵌合体，而无需骨髓毒性调节。我们将研究这种情况发生的机制，并确定移植物中哪些细胞类型对诱导耐受性至关重要。暴露于凋亡供体抗原的P-preDC通过产生Treg在体外有效耐受。这种方法的治疗应用尚未在体内测试。在AIM III中，我们将使用骨髓的体外免疫调节来扩增p-preDC和FC，并诱导用于HSC移植的耐受原性接种物。

DESCRIPTION (provided by applicant): The focus of this proposal is to develop a novel "conditioning" approach that will replace myelotoxic agents to establish chimerism in NOD mice. We will induce immune deviation to promote host-versus-graft hyporesponsiveness, thereby giving the hematopoietic stem cell (HSC) an opportunity to engraft and establish subsequent self-perpetuating deletional tolerance to islet allografts. Our recent studies in a mouse model suggest that the primary role for conditioning for HSC transplantation is to suppress host-versus-graft alloreactivity, rather than to prepare vacant niches in the recipient's bone marrow compartment. This observation suggests that one could replace myelotoxic agents with antigen-specific approaches to induce host-versus-graft hyporeactivity or anergy at the time of HSC transplantation. As the mechanisms underlying T cell activation are defined, highly specific approaches to suppress this alloreactivity have emerged. In AIM I. we will ESTABLISH CHIMERISM THROUGH IMMUNE DEVIATION OF THE RECIPIENT. We will immunomodulate the recipient: (a) targeting alloreactive cells in the host microenvironment; (b) inducing anergy and/or antigen-specific apoptosis of alloreactive host cells; and (c) through generation of regulatory T cells (Treg), and develop a novel nonmyeloablative conditioning regimen to induce antigen-specific hyporesponsiveness to the HSC and islet allografts. Cell-based therapies have great potential for inducing transplantation tolerance. Of greatest interest are the new subpopulations of bone marrow-derived dendritic cells (DC) that have recently been shown to be potently tolerogenic in vitro under certain circumstances. We are the first to demonstrate an in vivo engraftment-enhancing effect for precursor plasmacytoid DC (p-preDC). The exploitation of this discovery in vivo and its potential to reduce the need for myelotoxic conditioning has not yet been tested. Hematopoietic growth factors have also been used to drive the immune response to a tolerogenic T helper 2 (Th2) phenotype through production of p-preDC or other tolerance-promoting cells (graft facilitating cells {FC}) that in turn generate Treg. In AIM II, we will USE PRE-TRANSPLANT IMMUNOMODULATION OF THE DONOR WITH HEMATOPOIETIC GROWTH FACTORS TO GENERATE TOLEROGENIC CELLS IN THE HSC ALLOGRAFT. We will use these factors and the cells they generate to modulate the tolerogenicity of the donor marrow inoculum in vivo to tip the immune milieu in favor of graft acceptance, enhancing bone marrow chimerism without myelotoxic conditioning. We will examine the mechanism by which this occurs and identify which cell types in the graft are critical to tolerance induction. P-preDC exposed to apoptotic donor antigens are potently tolerizing in vitro through generation of Treg. The therapeutic application of this approach has not been tested in vivo. In AIM III, we will USE EX VIVO IMMUNOMODULATION OF THE MARROW to expand p-preDC and FC and induce a tolerogenic inoculum for HSC transplantation.