Depletion, Repopulation and Tolerance in Non-Sensitied Recipients

肾移植的巨大益处被与长期免疫抑制治疗相关的许多并发症所抵消。超过95%的患者使用基于钙调磷酸酶抑制剂（CNI）的方案，但这些方案不加选择地损害免疫过程，包括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CD 28-CD 80/86通路抑制，已被证明可以促进长期同种异体移植物存活，副作用比CNI少，最近的临床试验表明，淋巴细胞耗竭促进基于CoB的方案，不仅预防排斥反应，而且促进适应性过程，随着时间的推移减少对免疫抑制的需求，并促进同种异体耐受。该项目旨在确定淋巴细胞耗竭的要素，促进基于CoB的耐受性。我们已经表明，淋巴细胞耗竭和随后的稳态再增殖提供了塑造同种异体反应性免疫库以促进耐受的机会，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反应性克隆的激活。我们的实验计划试图理解消耗感应的这两个方面。我们假设治疗性淋巴细胞耗竭的有效性不是由CoB抗性细胞的直接消除驱动的，而是通过产生淋巴细胞更新和胸腺输出的刺激，促进抗原特异性激活诱导的细胞死亡（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增殖，后者由残留淋巴细胞群体对抗原暴露、次级淋巴器官功能和免疫抑制作用的相对（而非绝对）、成熟定义的耐受性控制。我们认为，这些因素是易处理的，可以治疗操纵。为了探索这一点，我们提出了3个具体目标：具体目标1：我们将定义耗竭诱导方案（广泛的多克隆或靶向单克隆抗体介导的耗竭）在接受肾移植的恒河猴中的作用，比较CNI和mTOR抑制剂对稳态再增殖的作用，并将这些与贝拉西普诱导的耐受性的疗效相关。具体目标2：我们将确定胸腺或脾脏切除或照射对同种异体细胞的稳态再增殖的影响。具体目标3：我们将确定供体和病毒（CMV）抗原暴露对再增殖和耐受性的影响，以骨髓或间充质干细胞的形式提供长期供体抗原，并在CMV幼稚动物和胸腺照射动物中研究这些方案。所有研究都将得到大量的机械支持，以评估表型、特异性和重建库的功能。我们将与项目2合作，确定这些操作对同种抗体形成的影响，并将项目中的结果与项目2的结果进行矩阵分析，以建立一个范例，指导开发与CoB配对的优化耗竭方案。

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.