Tolerance Induction to Islet Transplants

描述（由申请人提供）：本提案的重点是开发一种新的“调节”方法，取代骨髓毒性药物，在NOD小鼠中建立嵌合。我们将诱导免疫偏差来促进宿主对移植物的低反应性，从而给造血干细胞（HSC）一个移植的机会，并建立随后对胰岛异体移植物的自我延续的缺失耐受性。我们最近在小鼠模型中的研究表明，调节HSC移植的主要作用是抑制宿主对移植物的同种异体反应，而不是在受体骨髓腔室中准备空的壁龛。这一观察结果表明，在HSC移植时，可以用抗原特异性方法代替髓毒性药物来诱导宿主对移植物的低反应性或能量。随着T细胞活化机制的明确，抑制这种同种异体反应的高度特异性方法已经出现。在AIM i中，我们将通过受体的免疫偏差建立嵌合。我们将对受体进行免疫调节：(a)靶向宿主微环境中的同种异体反应细胞；(b)诱导同种异体反应性宿主细胞的能量和/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调节方案，以诱导对HSC和胰岛异体移植物的抗原特异性低反应性。细胞疗法在诱导移植耐受方面具有很大的潜力。最令人感兴趣的是骨髓来源的树突状细胞（DC）的新亚群，它们最近被证明在体外某些情况下具有潜在的耐受性。我们首次证明了前体浆细胞样DC （p-preDC）的体内植入增强作用。这一发现在体内的利用及其减少骨髓毒性调节需求的潜力尚未经过测试。造血生长因子也被用于通过产生p-preDC或其他促进耐受性的细胞（移植物促进细胞{FC}）来驱动对耐受性T辅助2 （Th2）表型的免疫反应，这些细胞反过来产生Treg。在AIM II中，我们将利用造血生长因子对供体进行移植前免疫调节，在同种造血干细胞移植体中产生耐受性细胞。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的耐受性，使免疫环境有利于移植物的接受，增强骨髓嵌合而不产生骨髓毒性。我们将研究发生这种情况的机制，并确定移植物中哪些细胞类型对耐受性诱导至关重要。暴露于凋亡供体抗原的P-preDC通过Treg的产生在体外具有强耐受性。这种方法的治疗应用尚未在体内进行测试。在AIM III中，我们将使用体外骨髓免疫调节来扩增p-preDC和FC，并诱导HSC移植的耐受原性接种。

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.