The role of complement component 3 in red blood cell alloimmunization

 描述(申请人提供)：反复输血可导致针对RBC同种异体抗原的同种异体抗体的形成，RBC表面的抗原能够在缺乏特定抗原的个体中诱导抗体形成。这些红细胞同种异体抗体增加了溶血性输血反应的风险，并使寻找相容的红细胞用于未来输血变得困难。然而，红细胞同种异体抗原如何诱导同种异体抗体的机制(S)以及输血不相容后导致红细胞清除的潜在途径仍然知之甚少。Kel糖蛋白是最具免疫原性的红细胞同种异体抗原之一，也是与溶血性输血反应和胎儿和新生儿溶血性疾病有关的最常见的同种异体抗原之一。因此，我们开发了一种在小鼠红细胞上特异性表达人Kel糖蛋白的小鼠模型，以了解导致RBC诱导的同种异体抗体形成的因素及其后果。在初步结果中，我们发现，将Kel红细胞输注到Kel免疫的C57BL/6(野生型)受体体内会导致快速清除阶段，随后清除动力学发生突变，从而使其余Kel红细胞对进一步的抗体介导的清除产生抵抗力。将KEL RBC输入免疫受者体内，发现KEL抗原发生了显著的改变，与RBC抵抗力的发展平行，这表明抗原调节在保护RBC免受额外抗体介导的去除中起到了作用。考虑到补体不仅可能参与促进抗体介导的清除，而且还参与抗原调节，我们研究了补体在这一过程中的潜在作用。我们发现，尽管在野生型小鼠中输注血型不合的KEL红细胞后KEL抗原水平降低，但在免疫的补体成分3(C3)基因敲除的KO小鼠中KEL的表达水平保持不变，强烈表明补体可能促进抗原调节。鉴于抗KEL抗体结合补体的能力和C3在促进针对其他抗原的抗体形成中的作用，我们研究了补体在KEL红细胞输注后抗KEL抗体形成中的潜在影响。与以前的研究相比，我们发现，将Kel红细胞输注到C3KO小鼠体内，实际上会显著增加抗Kel抗体的形成。考虑到C3在血型不合后调节KEL抗原的能力，以及在C3KO受者输血后形成的抗KEL抗体水平的增加，我们假设补体沉积可能掩盖了血型不合RBC输注后KEL抗原的免疫识别，从而降低了适应性免疫系统有效识别KEL抗原的能力，从而降低了对KEL抗原的应答能力。这些基础研究不仅将确定补体在KEL RBC清除和同种异体免疫中的作用，而且还将为潜在的治疗策略提供新的见解，旨在对抗RBC同种异体免疫的有害影响。

 DESCRIPTION (provided by applicant): Repeated blood transfusions can lead to formation of alloantibodies against RBC alloantigens, antigens on the RBC surface capable of inducing antibody formation in individuals who lack the particular antigen. These RBC alloantibodies increase the risk of hemolytic transfusion reactions and make it difficult to find compatible RBCs for future transfusions. However, the mechanism(s) of how RBC alloantigens induce alloantibodies and the potential pathways responsible for RBC clearance following incompatible transfusions remain poorly understood. The KEL glycoprotein is one of the most immunogenic RBC alloantigens and is also one of the most common alloantigens implicated in hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Therefore, we developed a mouse model that expresses the human KEL glycoprotein specifically on murine RBCs to understand the factors that contribute to the development and consequences of RBC-induced alloantibody formation. In preliminary results, we found that transfusion of KEL RBCs into KEL immunized C57BL/6 (wild-type) recipients results in a rapid clearance phase, followed by an abrupt change in clearance kinetics, such that the remainder of the KEL RBCs develop resistance to further antibody-mediated clearance. KEL RBCs transfused into immunized recipients displayed significant alterations to the KEL antigen that paralleled the development of RBC resistance, suggesting a role of antigen modulation in the protection of RBCs from additional antibody-mediated removal. Given the potential involvement of complement not only in facilitating antibody-mediated clearance, but also in antigen modulation, we examined the potential role of complement in this process. We found that although KEL antigen levels decrease following transfusion of incompatible KEL RBCs in wild-type mice, KEL expression levels remain unaltered in immunized complement component 3 (C3) knockout KO mice, strongly suggesting that complement may facilitate antigen modulation. Given the ability of anti-KEL antibodies to engage complement and the role of C3 in enhancing antibody formation to other antigens, we examined the potential impact of complement in the development of anti-KEL antibodies following KEL RBC transfusion. In contrast to previous studies, we found that transfusion of KEL RBCs into C3 KO mice actually resulted in a significant increase in anti-KEL antibody formation. Given the ability of C3 to modulate the KEL antigen following incompatible transfusion and the increased levels of anti- KEL antibody that form following transfusion into C3 KO recipients, we hypothesize that complement deposition may mask the KEL antigen from immunologic recognition following incompatible RBC transfusion and reduce the ability of the adaptive immune system to efficiently recognize and therefore respond to the KEL antigen. These fundamental studies will not only define the role of complement in KEL RBC clearance and alloimmunization, but will also provide novel insight into potential therapeutic strategies designed to combat the deleterious effects of RBC alloimmunization.