Analysis of T cell responses to platelet alloantigens

对血小板的免疫反应可能具有威胁性。输血后紫癜(PTP)可导致患者严重出血。新生儿同种异体免疫性血小板减少症(NIAT)会对新生儿造成伤害。这些疾病的基础是输血接受者或受影响婴儿的母亲产生同种抗体。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被相对忽视。这一遗漏需要解决，因为禁用T细胞帮助可以提供一种控制这些疾病的方法。在之前的资助期间，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中的专业知识来确定从作为反应目标的血小板蛋白中提取的多肽如何与人类白细胞抗原-DR抗原呈递分子相互作用。作为之前工作的结果，我们提出了一个临床相关的同种异体免疫模型，该模型将在该项目中进行测试。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(通常只有一种氨基酸)之间的差异控制着B细胞和T细胞的反应。对B细胞的控制可能是间接的，因为抗体可以识别整体形状。T细胞将识别包含这种多态的多肽。第二种假说认为，同种异体抗原肽的不同之处在于含有多态。第二种假设认为，同种异体抗原肽和相应的自体多肽之间的差异是允许多肽与人类白细胞抗原DR结合的。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在一个血小板同种异体抗原反应中的观察，我们在这个例子上进行推广。这一假设的基本原理是，通过允许多肽结合，这种多态产生了一种免疫系统以前从未见过的新抗原。这与别肽的刺激作用相反，因为别肽必须克服免疫系统先前接触过类似的自体多肽而诱导的耐受性。如果相应的自体多肽不能结合，就没有耐受性需要克服。该项目将分别对目标1和目标2的一些血小板同种异体抗原系统检验这两个假说。在目标3中，我们建议检验这些假设，通过证明我们可以控制同种免疫过程的参数并通过受控免疫产生同种免疫来检验这些假设。作为这一目标的一部分，我们将培育表达人类同种异体抗原系统之一的小鼠。这将使我们能够操纵动物，进一步了解在妊娠输血过程中同种异体免疫的重要变量。最后，因为我们已经确定了同种异体多肽和抗原递呈分子，所以我们建议对这些多肽进行修饰，以确定是否可以诱导T细胞拮抗。这种拮抗作用将在NAIT或PTP病例的T细胞培养中进行研究，也将在小鼠模型系统中进行研究。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.