Pathobiology of Incompatible transfusion

描述（由申请人提供）：红细胞（RBC）输注是急性创伤中的一种救生措施，是骨髓疾病和血红蛋白病的生命维持治疗，也是各种不同病理的医疗支持的重要组成部分。产生针对供体红细胞的同种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。尽管严格避免不相容输血，但由于溶血的风险，溶血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的健康献血者具有抗RBC自身抗体。因此，似乎存在适当的生物学机制，通过该机制宿主组织可以避免自身抗体或同种抗体的破坏。尽管供体红细胞有抗体包被，但为什么一些输血不会导致溶血，这一点还不太清楚。我们已经开发了几种不相容的红细胞输注的小鼠模型，使用真实的人血型抗原，其中不相容的输注不会溶血。在某些情况下，攻击性抗原从RBC中丢失而不损害RBC，然后RBC正常循环。这种现象（称为抗原丢失）已经在人类中对许多血型抗原进行了很好的描述，但只有很少的机制理解。据我们所知，我们已经描述了从红细胞抗原损失的唯一模型。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RBC的清除;然而，存活的RBC似乎代表了对正常溶血机制具有抗性的独特群体。在溶血性输血反应后循环中具有持续DAT阳性供体RBC的人中可以观察到相同的生物学。如上所述，据我们所知，我们描述了该过程的唯一动物模型。在这项研究中，我们提出了一个假设驱动的阐明机制的抗原损失和溶血抗性。这些发现不仅与抗体结合RBC的生物学有关，而且更广泛地与抗体直接结合组织的任何过程有关。RBC的独特优势在于它们既不合成新蛋白质也不经历分裂，提供了稳定的底物，在其上分析抗体结合和随后的生物学过程（例如补体激活、Fc γ受体连接等）期间的蛋白质和细胞变化。我们提出了具体的努力，以保持小鼠系统的易处理的性质，同时逐步人源化的模型，包括人RBC抗原，人Fc γ受体，和人源化抗体。我们提出三个具体目标。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：溶血抗性的分子和细胞机制。特定目的3：鼠和人IgG亚型对抗原丢失和抗溶血性的影响。

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.