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的金标准。它提供了比透析更好的质量和更长的寿命。然而，等候名单上有一半的病人处于不利地位，因为他们之前接触过人体组织，要么是接受输血，要么是怀孕，要么是肾移植失败，这导致他们中的一些人对一种叫做人类白细胞抗原（HLA）的组织蛋白“敏感”。这是通过血液循环中HLA抗体（Ab）的出现来检测的。HLA致敏大大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期间死亡的机会，也导致肾脏移植后寿命缩短。后一个问题的出现是因为患者的免疫系统被敏化“增强”，从而引起更积极的排斥反应，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，对于导致一些患者变得敏感而另一些患者仍然不敏感的生物学机制知之甚少，并且对于为什么不同的致敏途径（例如，怀孕与以前的移植）似乎会促进不同的问题知之甚少。毫不奇怪，没有可靠的方法来防止过敏。该项目将试图了解促进或防止致敏的生物学机制。我希望我的发现将为防止过敏的新策略提供基础。我的假设是，患者自然免疫调节机制的差异，主要是由一种称为“调节性T细胞”或Tregs的特定细胞介导的，是区分那些变得敏感的人与那些不敏感的人的原因，这些细胞支撑着患者因怀孕或以前的移植而变得敏感时所看到的差异。treg作为一种抑制炎症反应和预防自身免疫性疾病的防御机制存在于自然界中，但由各种不同类型的treg组成，其效力、稳定性和在某些组织之间移动的能力各不相同。我将研究treg的数量和不同亚型的混合，在移植失败的过渡到透析的患者中，以及怀孕的肾脏患者（他们将是主要的非移植患者）。此外，我将对患者Tregs抑制其他T细胞的功能能力进行分析，并使用最近描述的一种测定方法，抑制B细胞制造Ab。我希望显示那些产生HLA Ab的人与那些没有产生HLA Ab的人之间Tregs的差异，并显示怀孕期间的Tregs在表型和功能能力上与移植失败的人不同。我的项目的最后一部分更具探索性，并着眼于提高所有treg抑制致敏能力的潜在策略。它建立在我在ACF研究项目中产生的初步数据之上。treg可以受到多种不同信号的影响，包括通过多种不同受体起作用的炎症信号。根据我的导师未发表的工作，我证明了人类Treg表达一个叫做蛋白酶激活受体（PAR）的受体家族，其中一个成员（PAR-4）似乎被基本刺激以降低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。这一策略可能在未来任何基于增强treg抑制能力以防止HLA致敏的干预中被证明是有价值的辅助手段。

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.