Pathobiology of Incompatible transfusion

描述(申请人提供)：输注红细胞(RBCs)是急性创伤中的一种救命手法，是对骨髓疾病和血红蛋白疾病的维持生命治疗，也是各种不同病理的医疗支持的重要组成部分。产生针对供者红细胞的同种异体抗体可能是输血治疗的主要障碍，特别是在需要长期输血的患者中。虽然严格避免了血型不合的输血，但由于溶血的风险，溶血并不是血型不合的必然结果。相反，许多不相容的输血都没有溶血的迹象或症状。同样，多达1000名健康献血者中有1人拥有抗红细胞自身抗体。因此，似乎存在生物机制，宿主组织可以通过这些机制避免自身抗体或同种抗体的破坏。尽管供体红细胞包被了抗体，但人们对一些输血不会导致溶血的原因还知之甚少。我们已经用正宗的人类血型抗原建立了几种不相容的小鼠红细胞输注模型，在这些模型中，不相容的输血不会溶血。在某些情况下，有害的抗原从红细胞中丢失，而不损害红细胞，然后红细胞正常循环。这种现象(称为抗原丢失)已经在人类中对一些血型抗原进行了很好的描述，但对其产生的机制了解很少。就我们所知，我们已经描述了红细胞抗原丢失的唯一模型。我们同样描述了第二种模型，在这种模型中，输血不相容会导致大多数红细胞被清除；然而，存活下来的红细胞似乎代表了一个独特的群体，对正常的溶血机制具有抵抗力。在溶血性输血反应后循环中持续存在DAT阳性供者红细胞的人中也可以观察到同样的生物学特性。如上所述，就我们所知，我们已经描述了这一过程的唯一动物模型。在这项授权中，我们提出了一个假说，以阐明抗原丢失和溶血抵抗的机制。这些发现不仅与抗体结合红细胞的生物学相关，而且更广泛地与抗体直接与组织结合的任何过程有关。红细胞具有独特的优势，因为它们既不合成新的蛋白质，也不经历分裂，提供了一个稳定的底物，用于分析抗体结合和随后的生物学过程(如补体激活、Fcγ受体连接等)过程中蛋白质和细胞的变化。我们建议采取具体措施来维持小鼠系统的易操纵性，同时逐步使模型人性化，包括人RBC抗原、人Fcγ受体和人源化抗体。我们提出了三个具体目标。具体目标1：非溶血性抗原丢失的分子和细胞机制。具体目标2：溶血抵抗的分子和细胞机制。特异性目标3：小鼠和人免疫球蛋白亚型对抗原丢失和抗溶血作用的影响。

DESCRIPTION (provided by applicant): Transfusion of red blood cells (RBCs) is a life saving maneuver in acute trauma, a life sustaining treatment for diseases of the bone marrow and hemoglobinopathies, and an important component of medical support for a variety of different pathologies. Generation of alloantibodies against donor RBCs can be a major impediment to transfusion therapy, especially in patients who require chronic transfusion. Although incompatible transfusion is strictly avoided, because of the risks of hemolysis, hemolysis is not the inevitable outcome of incompatible transfusion. On the contrary, many incompatible transfusion are given with no signs or symptoms of hemolysis. Likewise, up to 1/1000 healthy blood donors have anti-RBC autoantibodies. Thus, it appears that there are biological mechanisms in place by which host tissues can avoid destruction from their own antibodies or alloantibodies. It is only poorly understood why some transfusions do not result in hemolysis, despite antibody coating of donor RBCs. We have developed several murine models of incompatible RBC transfusion, using authentic human blood group antigens, in which incompatible transfusions do not hemolyze. In some cases, the offending antigen is lost form the RBC without damaging the RBC, which then circulates normally. This phenomenon (called antigen-loss) has been well described in humans for a number of blood group antigens, but only very little mechanistic understanding has been generated. To the best of our knowledge, we have described the only model of antigen loss from RBCs. We have likewise described a second model in which an incompatible transfusion leads to the clearance of most RBCs; however, the RBCs that survive appear to represent a distinct population that is resistant to normal hemolytic mechanisms. This same biology can be observed in humans who have persistent DAT positive donor RBCs in circulation after a hemolytic transfusion reaction. As above, to the best of our knowledge, we have described the only animal model of this process. In this grant, we propose a hypothesis driven elucidation of the mechanisms of both antigen-loss and hemolysis resistance. These findings have potential relevance not only to the biology of antibody binding RBCs, but more broadly to any process in which an antibody is bound directly to a tissue. RBCs give a unique advantage in that they neither synthesize new protein nor undergo division, providing a stable substrate upon which to analyze protein and cellular changes during the process of antibody binding and subsequent biologies (e.g. complement activation, Fc gamma receptor ligation, etc.) We propose specific efforts to maintain the tractable nature of murine systems while progressively humanizing the models, including human RBC antigens, human Fc gamma receptors, and humanized antibodies. We propose 3 specific aims. Specific Aim 1: Molecular and Cellular Mechanisms of Non-Hemolytic Antigen-Loss. Specific Aim 2: Molecular and Cellular Mechanisms of Hemolysis Resistance. Specific Aim 3: Effects of Murine and Human IgG Subtype on Antigen-Loss and Hemolysis Resistance.