Pathobiology of Incompatible transfusion

描述（由申请人提供）：红细胞（rbc）的输血是急性创伤的救命手段，是骨髓疾病和血红蛋白病的维持生命的治疗方法，是各种不同病理的医疗支持的重要组成部分。产生针对供体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。虽然严格避免不相容输血，但由于存在溶血的风险，溶血并不是不相容输血的必然结果。相反，许多不相容的输血没有溶血的迹象或症状。同样，高达1/1000的健康献血者有抗红细胞自身抗体。因此，宿主组织避免自身抗体或同种异体抗体破坏的生物学机制似乎存在。尽管供体红细胞有抗体包被，但有些输血不导致溶血的原因尚不清楚。我们已经开发了几种不相容红细胞输血的小鼠模型，使用真实的人类血型抗原，其中不相容输血不溶血。在某些情况下，攻击抗原从红细胞中消失而不损害红细胞，然后红细胞正常循环。这种现象（称为抗原丢失）已经在人类的许多血型抗原中得到了很好的描述，但只有很少的机制理解已经产生。据我们所知，我们已经描述了唯一的红细胞抗原丢失模型。我们同样描述了第二种模型，其中不相容的输血导致大多数红细胞的清除；然而，存活下来的红细胞似乎代表了一个独特的群体，对正常的溶血机制有抵抗力。在溶血输血反应后供体红细胞持续呈DAT阳性的人体内也可观察到同样的生物学现象。如上所述，据我们所知，我们描述了这一过程的唯一动物模型。在这项资助中，我们提出了一个假设驱动的阐明抗原损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有关，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，即它们既不合成新蛋白，也不进行分裂，为分析抗体结合过程中的蛋白质和细胞变化提供了稳定的底物（如补体活化、Fc γ受体连接等）。我们建议在逐步人源化模型的同时，努力保持小鼠系统的可处理性，包括人类红细胞抗原、人类Fc γ受体、还有人源化抗体。我们提出3个具体目标。特异性目标1：非溶血性抗原丢失的分子和细胞机制。特异性目标2：溶血抵抗的分子和细胞机制。特异性目的3：小鼠和人IgG亚型对抗原丢失和溶血抵抗的影响。

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.