Analysis of T cell responses to platelet alloantigens

对血小板的免疫反应可能是有威胁的。输血后紫癜（PTP）可导致严重出血的个人。新生儿同种免疫性血小板减少症（NIAT）可危害新生儿的健康。这些疾病是基于输血接受者或受影响婴儿的母亲产生的同种异体抗体。一般来说，C细胞产生任何抗体都需要T细胞的帮助。虽然同种异体抗体反应一直是许多研究的主题，但T细胞在这一过程中的作用相对被忽视。这种遗漏需要解决，因为使T细胞失能的帮助可以提供一种控制这些疾病的方法。在之前的资助期内，我们一直在开发研究T细胞反应的新方法，并一直在分析T细胞在血小板减少症中的作用。我们还利用我们在免疫遗传学方面的专业知识来确定从血小板蛋白中提取的肽是如何与HLA-DR抗原呈递分子相互作用的。由于之前的工作，我们提出了一个临床相关的同种免疫模型，将在本项目中进行测试。该模型由两个假设组成。第一种观点认为，免疫蛋白和应答者自身蛋白（通常只有一个氨基酸）之间的差异控制着B细胞和T细胞的应答。B细胞的控制可能是间接的，因为抗体识别整体形状。T细胞会识别包含多态性的肽。第二种假说提出，异体抗原之间的差异包括多肽的多态性。第二种假说认为，同种异体抗原肽与相应的自肽之间的区别在于允许肽与HLA-DR结合。这种多肽加DR的组合是T细胞受体识别的实际结构。第二个假设是基于我们对一个血小板异体抗原反应的观察，我们对这个例子进行了概括。这一假设的基本原理是，通过允许肽结合，多态性产生了一种免疫系统以前从未见过的新抗原。这与同种异体肽必须克服免疫系统先前暴露于类似的自肽引起的耐受性的刺激是一致的。如果相应的自肽不能结合，就没有耐受性可以克服。本项目将分别对多个血小板异体抗原系统作为目标1和目标2来检验这两个假设。在Aim 3中，我们提出要测试，我们提出要测试这些假设，通过显示我们可以控制同种异体免疫过程的参数，并通过控制免疫产生同种异体免疫。作为这一目标的一部分，我们将产生表达一种人类异体抗原系统的小鼠。这将使我们能够操纵动物，以进一步了解在妊娠输血期间同种异体免疫的重要变量。最后，由于我们已经确定了同种异体肽和抗原呈递分子，我们建议修改这些肽，以确定是否有可能诱导T细胞拮抗。我们将在NAIT或PTP病例培养的T细胞以及小鼠模型系统中研究这种拮抗作用。从本项目中描述的研究中获得的知识可以为干预这些疾病的新方法提供基础。

Immune responses to platelet can be threatening. Post-transfusion purpura (PTP) can result in serious bleeding in the affected individual. Neonatal alloimmune thrombocytopenia (NIAT) can harm the or the newborn. These disorders are based on the generation of alloantibodies by the transfusion recipient or by the mother of the affected infant. In general, the generation of any antibody by C cells requires T cell help. While the alloantibody response has been the subject of many studies, the role of T cells in the process has been relatively neglected. This omission need addressing as disabling T cell help could provide a way to control these disorders. In the previous funding period we have been developing novel approaches to study T cell responses and have been analyzing the role of T cells in thrombocytopenia. We have also utilized our expertise im immunogenetics to determine how peptides, derived from platelet proteins that are the targets of the response, could be interacting with the HLA-DR antigen presentation molecules. As a result of this previous work, we propose a model of clinically relevant alloimmunity that will be tested in this project. This model is composed of two hypotheses. The first proposes that the difference between the immunizing protein and the responder's self protein (often only one amino acid) controls both the B cell and T cell responses. The control of the B cell may be indirect as antibodies recognize overall shapes. The T cells will recognize the peptide that includes the polymorphism. The second hypothesis proposes that the difference between the alloantigen peptide that includes the polymorphism. The second hypothesis proposes that the difference between the alloantigen peptide and the corresponding self-peptide is one that allows the peptide to bind to the HLA-DR. This combination of peptides plus DR is the actual structure recognized by T cell receptor. The second hypothesis is based on our observations in one platelet alloantigen response and we generalize on this example. The rationale for this hypothesis is that by allowing the peptide to bind, the polymorphism has generated a new antigen that has not been previously seen by the immune system. This is in contract to the stimulation of the allopeptide having to overcome the tolerance induced by the immune system having been previously exposed to the similar self-peptide. If the corresponding self- peptide cannot bind, there is no tolerance to overcome. This project will test these two hypothesis for a number of platelet alloantigen systems as Aims 1 and 2 respectively. In Aim 3, we propose to test, we propose to test these hypothesis by showing that we can control the parameters of the alloimmunization process and generate alloimmunity by controlled immunizations. As part of this aim, we will generate mice expressing one of the human alloantigen systems. This will enable us to manipulate the animals to further understand the variables important in alloimmunization during transfusion of pregnancy. Finally, because we will have identified the allogeneic peptides and antigen presentation molecules, we propose to modify the peptides to determine if it is feasible to induce T cell antagonism. The antagonism will be studied both in cultured T cells from NAIT or PTP cases, but also in the mouse model system. The knowledge gained from the studies described in this project can provide the basis for novel approaches to intervention in these disorders.