Regulatory T cells in Highly Sensitised Renal Patients to Improve Outcomes after HLA-Antibody Incompatible Transplantation.

肾移植是治疗肾衰竭的金标准。它提供了比透析更好的质量和更长的寿命。然而，三分之一等待肾移植的患者对一种叫做人类白细胞抗原（HLA）的组织蛋白高度敏感，要么是通过之前的输血、怀孕，要么是之前的肾移植，这导致血液循环中出现针对HLA的抗体（Ab）。Ab型血显著增加了等待合适肾脏的时间。这些患者有两种选择：要么长时间等待透析以获得匹配的器官，要么在移植前进行“脱敏”以去除Ab；主管AD和他的同事的工作表明，与等待透析相比，这种方法提供了相同的患者生存率。尽管“脱敏”为这些患者提供了一种移植方法，但由于免疫“记忆”的存在，他们通常会在几天内对肾脏产生积极的免疫反应，这些免疫反应存在于免疫系统的细胞中；因此，这些患者有较高的早期排斥反应、“闷烧”或慢性排斥反应和移植物衰竭的发生率，并且由于他们接受较高水平的免疫抑制来预防和治疗这些并发症，感染并发症的发生率也较高。因此，这些患者的移植结果不如非致敏受体。AD之前的研究强调，一些（但不是所有）对HLA敏感的患者能够抑制记忆免疫反应，这是因为他们保留了一种称为调节性T细胞（Tregs）的特化细胞，这种细胞在自然界中作为一种防御机制存在，可以抑制炎症反应和预防自身免疫性疾病。因为我们知道，从他们的HLA Ab谱中，患者对特定的HLA敏感，因为特定的HLA蛋白现在可以作为高度纯化的重组蛋白在商业上获得，所以可以使用ELISPOT测定法来测试个体的记忆反应。我项目的第一部分将是研究高度敏感患者中treg的数量和特征，并测试它们是否保留抑制对特定HLA蛋白的反应的能力。出于实际目的，我将把我的分析限制在最多20名患者中，并研究他们具有低水平Ab的HLA。导师GL是Treg群体分离和扩增方面的专家，迄今为止，他在2项英国试验中监督了临床级细胞移植患者的管理。我项目的第二部分将是从患者身上分离和扩增特定的treg亚群，以测试这些亚群是否可以在体外通过ELISPOT测定来抑制对HLA的反应，作为替代，如果我们给这些患者注射treg可能会发生什么。我还将测试操纵treg，以增强它们与记忆细胞相互作用的能力，是否会增强它们的抑制能力。该项目的这一部分将为这些患者的治疗性Treg试验的未来方向提供信息。最后，两位主管目前正在计划在2019年对移植等待名单上的患者进行临床级Tregs的试验，目前正在准备资金申请。该试验的目的是评估是否有可能可靠地检测treg对HLA记忆反应的影响。因此，我的项目的第三部分将是研究ELISPOT对试验患者中特定HLA蛋白的反应，特别是询问第1部分和第2部分的体外观察是否可以通过在体内给药Tregs来复制。我在这部分的工作将直接影响到是否会进行第二次治疗试验，比较Tregs和传统疗法对即将接受移植的患者的影响。

Kidney transplantation is the gold-standard treatment for patients with kidney failure. It offers a better quality and longer life than the alternative, which is dialysis. However, one-third of patients awaiting a kidney transplant are highly sensitized to tissue proteins called human leukocyte antigens (HLA), either through a previous blood transfusion, pregnancy, or a prior kidney transplant, which results in the appearance of antibodies (Ab) against HLA in the circulation. The Ab significantly increase the time spent awaiting a suitable kidney. These patients have two options: either wait a long time on dialysis for a matched organ or undergo 'desensitization' to remove Ab before transplantation; work from the supervisor AD and his colleagues have shown that this approach offers equivalent patient survival compared to waiting on dialysis.Although 'desensitization' offers a way to transplant these patients, they mount aggressive immune responses to the kidney, usually within a few days, consequent on the presence of immunological 'memory', residing within cells of the immune system; therefore, these patients have higher rates of early rejection, 'smouldering' or chronic rejection and graft failure and, because of the higher levels of immunosuppression they receive to prevent and treat these complications, a higher rate of infectious complications. Therefore, transplant outcomes in these patients are inferior to those seen in non-sensitized recipients.Previous work from supervisor AD has highlighted that some, but not all patients who are sensitized to HLA are able to suppress memory immune responses, by virtue of the fact they retain specialized cells called regulatory T cells (Tregs), which exist in nature as a defence mechanism to suppress inflammatory responses and prevent autoimmune diseases. Because we know, from their HLA Ab profiles, the specific HLA to which patients are sensitized, and because specific HLA proteins are now commercially available as highly purified recombinant proteins, it is possible to test memory responses in individuals using assays called ELISPOT assays. The first part of my project will be to study the numbers and characteristics of Tregs in highly sensitized patients and test whether they retain the ability to suppress responses to specific HLA proteins. For practical purposes, I will limit my analysis to a maximum of 20 patients and study the HLA to which they have low-level Ab. The supervisor GL is an expert on the isolation and expansion of Treg populations and has so far supervised the administration of clinical grade cells to transplant patients in 2 UK trials. The second part of my project will be to isolate and expand particular subpopulations of Tregs from patients to test whether these can be used in vitro to suppress the responses to HLA by titrating into the ELISPOT assay, as a surrogate for what might happen if we were to administer Tregs to these patients. I will also test whether manipulating Tregs, to enhance their ability to interact with memory cells, enhances their suppressive ability. This part of the project will inform the future direction of therapeutic Treg trials in these patients.Finally, both supervisors are currently planning a trial to administer clinical grade Tregs to patients on the transplant waiting list in 2019 - at present, a request for funding is being prepared. The purpose of the trial will be to assess whether it is possible to robustly detect the impact of Tregs on memory responses to HLA. Therefore the third part of my project will be to study ELISPOT responses to specific HLA proteins in the trial patients, specifically to ask whether the in vitro observations in part 1&2 can be reproduced by administering Tregs in vivo. My work in this part will have a direct bearing on whether a second therapeutic trial, comparing Tregs to conventional therapy in patients about to be transplanted, is performed.