Tolerance Induction to Islet Transplants

描述(申请人提供)：这项提议的重点是开发一种新的“条件作用”方法，将取代骨髓毒性药物来建立NOD小鼠的嵌合体。我们将诱导免疫偏离以促进宿主对移植物的低反应，从而使造血干细胞(HSC)有机会植入，并建立随后对同种异体胰岛移植的自持性缺失耐受。我们最近在小鼠模型中的研究表明，HSC移植的条件作用主要是抑制宿主对移植物的同种异体反应，而不是在受者的骨髓室中准备空置的壁龛。这一观察表明，在HSC移植时，可以用抗原特异性方法取代骨髓毒性药物，以诱导宿主对移植物的低反应性或无效性。随着T细胞激活机制的确定，出现了抑制这种同种异体反应的高度特异性的方法。在目的I中，我们将通过受体的免疫偏离建立嵌合体。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性细胞；(B)诱导同种异体反应性宿主细胞的无能和/或抗原特异性凋亡；以及(C)通过产生调节性T细胞(Treg)，并开发一种新的非清髓性预适应方案，以诱导对HSC和同种异体胰岛移植物的抗原特异性低反应。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，最近被证明在某些情况下在体外具有潜在的耐受性。我们首次证实了前体血浆细胞样树突状细胞(p-preDC)的体内植入增强效应。这一发现在体内的开发及其减少骨髓毒性调节需求的潜力尚未得到测试。造血生长因子也被用来通过产生p-preDC或其他促进耐受的细胞(移植物促进细胞{FC})来驱动对耐受性T辅助细胞2(Th2)表型的免疫反应，这些细胞继而产生Treg。在AIM II中，我们将利用供者移植前的免疫调节和造血生长因子在HSC同种异体移植中产生耐受细胞。我们将利用这些因子及其产生的细胞在体内调节供者骨髓接种的耐受性，使免疫环境有利于移植物的接受，在没有骨髓毒性条件下增强骨髓嵌合体。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诱导至关重要。暴露于凋亡性供体抗原的P-preDC在体外通过产生Treg而具有强大的耐受性。这种方法的治疗应用还没有在体内进行测试。在AIM III中，我们将使用体外骨髓免疫调节来扩增p-preDC和FC，并诱导出适用于HSC移植的耐受性接种。

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.