Depletion, Repopulation and Tolerance in Non-Sensitied Recipients

肾移植的巨大益处被慢性免疫抑制治疗相关的许多并发症所抵消。超过95%的患者使用以钙调磷酸酶抑制剂（CNI）为基础的方案，但这些方案不加选择地损害免疫过程，包括那些促进移植物接受的免疫过程，并产生显著的副作用。共刺激阻断（CoB），特别是CD28-CD80/86通路抑制，已被证明可以促进同种异体移植物的长期存活，副作用比CNIs少，最近的临床试验表明，淋巴细胞消耗促进基于CoB的方案，不仅可以防止排斥反应，还可以促进适应性过程，减少对免疫抑制的需求，并促进异体特异性耐受性。该项目旨在定义促进cob基耐受性的淋巴细胞耗竭的要素。我们已经表明，淋巴细胞耗损和随后的稳态繁殖，提供了塑造同种异体免疫库以促进耐受性的机会，但也带来了破坏调节的风险，并引发病毒感染、自身免疫和同种异体克隆的激活。我们的实验计划试图理解耗竭诱导的这两个方面。我们假设，治疗性淋巴细胞消耗的有效性不是由直接消除cob耐药细胞驱动的，而是通过刺激淋巴细胞更新和胸腺输出，促进抗原特异性激活诱导细胞死亡（AICD）。从这个角度来看，消耗的方法从细胞消除转变为促进和管理再生群体，后者由残余淋巴细胞群体对抗原暴露、次级淋巴器官功能和免疫抑制的相对（而不是绝对）、成熟定义的敏感性控制。我们假设这些因素是可处理的，并且可以通过治疗来控制。为了探讨这一点，我们提出了3个具体目标：1：我们将定义消耗诱导方案（广泛的多克隆或靶向单克隆抗体介导的消耗）对接受肾移植的恒河猴的影响，比较CNIs和mTOR抑制剂对稳态再生种群的影响，并将其与belataccept诱导耐受性的功效联系起来。特异性目标2：我们将确定胸腺或脾脏切除或照射对同种异体细胞稳态再生的影响。特异性目标3：我们将确定供体和病毒（CMV）抗原暴露对再繁殖和耐受性的影响，以骨髓或间充质干细胞的形式提供长时间的供体抗原，并在CMV naïve动物（胸腺照射动物）中研究这些方案。所有的研究都将得到大量的机械支持，以评估表型、特异性和重新种群的功能。我们将与项目2合作，确定这些操作对同种异体抗体形成的影响，并将项目2的结果与项目2的结果进行对比，以建立一个范例，指导开发与CoB配对的优化消耗方案。

Kidney transplantation's considerable benefit is offset by the many complications associated with chronic immunosuppressive therapy. Calcineurin inhibitor (CNI)-based regimens are used by over 95% of patients, but these indiscriminately impair immune processes, including those that facilitate graft acceptance, and produce significant side effects. Costimulation blockade (CoB), particularly CD28-CD80/86 pathway inhibition, has been shown to promote long-term allograft survival with fewer side effects than CNIs, and recent clinical trials have suggested that lymphocyte depletion fosters CoB-based regimens, not only preventing rejection, but fostering adaptive processes that reduce the needs for immunosuppression with time, and promoting allospecific tolerance. This project seeks to define the elements of lymphocyte depletion that foster CoB-based tolerance. We have shown that lymphocyte depletion, and subsequent homeostatic repopulation, present opportunities to shape the alloreactive immune repertoire to favor tolerance, but also poses risks to disrupt regulation, and ignite viral infection, autoimmunity and activation of alloreactive clones. Our experimental plan seeks to understand these two sides of depletional induction. We hypothesize that the effectiveness of therapeutic lymphocyte depletion is NOT driven by direct elimination of CoB-resistant cells, but rather by creating a stimulus for lymphocyte turnover and thymic output, fostering antigen-specific activation induced cell death (AICD). Viewed this way, the approach to depletion changes from cell elimination, to promoting and managing repopulation, the latter controlled by relative (not absolute), maturation-defined susceptibilities of the residual lymphocyte population to the effects of antigen exposure, secondary lymphoid organ function, and immunosuppression. We posit that these factors are tractable, and can be therapeutically manipulated. To explore this, we propose 3 specific aims: Specific Aim 1: We will define the effects of depletional induction regimens (broad polyclonal or targeted monoclonal antibody mediated depletion) in rhesus monkeys undergoing kidney transplantation, comparing the effects of CNIs and mTOR inhibitors on homeostatic repopulation, and relate these to the efficacy of belatacept-induced tolerance. Specific Aim 2: We will define the impact of thymic or splenic resection or irradiation on homeostatic repopulation of allospecific cells. Specific Aim 3: We will define the impact of donor and viral (CMV) antigen exposure on repopulation and tolerance, providing prolonged donor antigen in the form of bone marrow or mesenchymal stem cells, and studying these regimens in CMV naïve animals, animals with thymic irradiation. All studies will be heavily mechanistically supported to assess the phenotype, specificity and function of the repopulating repertoire. We will partner with Project 2 to define the impact of these maneuvers on alloantibody formation, and matrix the results in the Project with those of Project 2 to establish a paradigm to guide the development of an optimized depletional regimen to pair with CoB.