Exploring the Links Between Regulatory T cell Populations and Development of HLA Antibodies in Renal Patients Awaiting Transplantation.

肾移植是治疗肾衰竭患者的金标准。与透析相比，它提供了更好的质量和更长的寿命。然而，在等待名单上的所有患者中，有一半是因为以前接触过人体组织而处于不利地位，要么是因为接受过输血，要么是因为怀孕，或者是因为肾移植失败，这导致他们中的一些人对称为人类白细胞抗原(HL A)的组织蛋白“敏感”。这是通过循环中出现的抗人类白细胞抗原抗体(Ab)来检测的。人类白细胞抗原敏感化显著增加了患者等待合适肾脏的时间，增加了患者在等待合适肾脏的过程中死亡的机会，而且一旦移植，也会导致肾脏寿命缩短。后一个问题之所以出现，是因为患者的免疫系统被敏感化增强，从而导致更具攻击性的排斥反应，类似于免疫系统从疫苗中获得的增强，以防止感染。令人惊讶的是，人们对导致一些患者变得敏感而另一些患者保持不敏感的生物学机制知之甚少，也更少知道为什么不同的敏化途径(例如，怀孕和以前的移植)似乎会促进不同的问题。不足为奇的是，没有可靠的方法来预防过敏。这个项目将试图了解促进或防止过敏的生物机制。我希望我的发现将为防止从根本上防止敏感的新战略提供基础。我的假设是，患者自然免疫调节机制的差异，主要是由一种特定类型的细胞介导的免疫调节机制，是敏感者与非敏感者的区别，这些细胞是患者因怀孕或之前的移植而变得敏感时所看到的差异的基础。Treg在自然界中作为一种防御机制存在，以抑制炎症反应和预防自身免疫性疾病，但由各种不同的类型组成，在效力、稳定性和在某些组织之间移动的能力上各不相同。我将研究移植失败患者过渡到透析的Tregs数量和不同亚型的组合，以及怀孕的肾脏患者(他们将是主要的非移植患者)。此外，我还将分析患者Tregs抑制其他T细胞的功能能力，并使用最近描述的一种方法来抑制B细胞产生抗体。我希望显示那些发展成人类白细胞抗原抗体的人和那些没有发展成人类白细胞抗原抗体的人之间的Treg的不同，并表明怀孕期间的Treg在表型和功能能力上与那些遭受移植失败的人不同。我的项目的最后部分更具探索性，着眼于一个潜在的战略，即增强所有特雷格人抑制敏感化的能力。它以我在ACF研究项目期间生成的初步数据为基础。Treg可以受到多种不同信号的影响，包括通过各种不同受体发挥作用的炎症信号。在我的主管未发表的工作之后，我发现人类Treg表达一种名为蛋白酶激活受体(PAR)的受体家族，其中一个成员(PAR-4)似乎受到碱基刺激，以降低Treg的抑制能力。我将尝试确定负责基础刺激的酶，以期表明抑制它，或抑制PAR-4信号，可以增强Tregs的抑制能力。这一策略可能被证明是未来任何基于增强Tregs抑制能力以防止HLA敏化的干预的有价值的辅助手段。

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, half of all patients on the waiting list are disadvantaged because of previous exposure to human tissues, either through receiving a blood transfusion, being pregnant, or having a failed kidney transplant, which results in some of them becoming 'sensitised' to tissue proteins called human leukocyte antigens (HLA). This is detected by the appearance of antibodies (Ab) against HLA in the circulation. HLA sensitisation significantly increases the time a patient spends waiting for a suitable kidney, increases the chance of a patient dying whilst awaiting a suitable kidney, and also causes a shortened life-span of a kidney once transplanted. The latter problem arises because the patients' immune system is 'boosted' by the sensitisation to cause more aggressive rejection, similar to the boost the immune system gets from a vaccine to protect against infection. Surprisingly little is known about the biological mechanisms that result in some patients becoming sensitised whilst others remain unsensitised, and less is known about why different routes of sensitisation (i.e. pregnancy vs. previous transplant, for instance), appear to promote different problems. Not surprisingly, there is no reliable way to prevent sensitisation.This project will attempt to understand the biological mechanisms that promote or prevent sensitisation. I hope my findings will provide the foundation for novel strategies to prevent sensitisation in all. My hypothesis is that differences in patients' natural immune regulatory mechanisms, primarily those mediated by a specific type of cell called 'Regulatory T cells' or Tregs, are what differentiates those who become sensitised from those who do not, and that these cells underpin the differences seen when patients become sensitised by pregnancy or a previous transplant. Tregs exist in nature as a defence mechanism to suppress inflammatory responses and prevent autoimmune diseases, but are made up of various different types, varying in potency, stability and ability to move between certain tissues. I will study the numbers of Tregs and the mix of the different subtypes in patients with a failing transplant who are transitioning onto dialysis, as well as renal patients who become pregnant (who will be in the main non-transplant patients). In addition, I will perform analyses of the functional capacity of patient Tregs to suppress other T cells, and using a recently described assay, to suppress B cell manufacture of Ab. I expect to show differences in Tregs between those who develop HLA Ab and those who do not, and to show that Tregs in pregnancy differ in phenotype and functional ability from those suffering a transplant failure. The final part of my project is more exploratory and looks towards a potential strategy of enhancing the ability of all Tregs to suppress sensitisation. It builds upon preliminary data I generated during my ACF research project. Tregs can be influenced by multiple different signals, including inflammatory signals that act through a variety of different receptors. Following on from unpublished work of my supervisors, I showed that human Tregs express a family of receptors called protease activated receptors (PAR), one member of which (PAR-4) appears to be basally stimulated to reduce Treg suppressive capacity. I will attempt to identify the enzyme responsible for the basal stimulation, with a view to showing that inhibiting it, or inhibiting PAR-4 signalling, can enhance the suppressive capacity of Tregs. This strategy may prove a valuable adjunct in any future intervention based upon enhancing the suppressive ability of Tregs to prevent HLA sensitisation.