Anti-HLA Antibody Activation of Endothelial Cells in Cardiac Transplantation

描述(由申请人提供)： 心脏移植受者对同种异体移植物表现出体液免疫反应，则会增加抗体介导的排斥反应和移植物动脉硬化的风险。人类白细胞抗原I类和II类信号通路参与了这一过程，因为抗人类白细胞抗原抗体将I类和II类分子连接起来，启动内皮细胞内信号，与生长因子受体协同作用，诱导细胞存活和增殖。当细胞暴露于低浓度的抗人类白细胞抗原抗体时，内皮细胞的抗凋亡和细胞生存机制的激活被增强。相反，用高浓度的抗人类白细胞抗原抗体处理内皮细胞会刺激细胞增殖。这提示低水平的抗HLA抗体通过激活促进移植物适应的存活信号通路而有利于移植物存活。另一方面，高水平的抗HLA抗体结合可能通过上调FGFR的表达，刺激细胞增殖，增加发生移植动脉硬化的风险，从而对移植物存活产生不利影响。我们认为这些发现在临床上是相关的，并可能解释产生抗供体人类白细胞抗原抗体的心脏移植患者移植结果的差异。该建议的总体目标是阐明由抗体连接I类和II类分子而引发的细胞内信号事件是否受人类白细胞抗原抗体的特异性和浓度的影响，并确定I类和II类信号通路在心脏移植中的临床相关性。拟议研究中使用的患者样本将来自“CTOT-05心脏移植受者同种异体免疫观察性研究”。CTOT-05研究是一项针对心脏移植受者的前瞻性、非随机、多中心、观察性临床试验。在目标1下，我们将研究心脏移植受者血清中抗人类白细胞抗原I类和II类抗体在内皮细胞中介导增殖和/或细胞存活信号的能力。血清中的免疫球蛋白组份将通过携带相关人类白细胞抗原的供体和代理内皮细胞中的MHC I类和II类分子来测试其传递信号的能力(S)。在目标2下，我们将评估抗人类白细胞抗原抗体诱导的蛋白磷酸化、成纤维细胞生长因子受体和抗凋亡蛋白在有和没有产生抗人类白细胞抗原抗体的同种异体心脏移植的临床活检标本中的表达。在抗体介导的排斥反应和移植动脉硬化的背景下，了解I类和II类信号通路对于开发新的诊断工具和治疗策略以改善患者管理和心脏移植结果具有重要意义。 与公众健康相关：在CTOT-05临床试验样本中研究抗人类白细胞抗原抗体介导的信号转导将使我们能够确定I类和II类信号通路在心脏移植结果中的重要性。这些研究将确定介导急性和慢性抗体介导的排斥反应的关键信号蛋白，并可能允许开发新的治疗策略。这项研究将开发和测试I类和II类抗体介导的信号转导作为移植结果的可靠指标，并为抗体介导移植物损伤的机制提供洞察力。(摘要结束)

DESCRIPTION (provided by applicant): Cardiac transplant recipients exhibiting a humoral immune response to the allograft demonstrate increased risk of antibody-mediated rejection and transplant arteriosclerosis. HLA class I and class II signaling pathways have been implicated in this process because ligation of class I and class II molecules by anti-HLA antibodies initiates intracellular signals in endothelial cells that synergize with growth factor receptors to elicit cell survival and cell proliferation. Activation of anti-apoptotic and cell survival machinery in endothelial cells is augmented when cells are exposed to low concentrations of anti-HLA antibodies. In contrast, treatment of endothelial cells with high concentrations of anti-HLA antibodies stimulates cell proliferation. This suggests that lower levels of anti-HLA antibody binding to HLA may be beneficial to graft survival by activating survival signaling pathways that promote graft accommodation. On the other hand, high levels of anti-HLA antibody binding may have a detrimental effect on graft survival by upregulating FGFR expression, stimulating cell proliferation and increasing risk for development of transplant arteriosclerosis. We believe these findings are clinically relevant and may explain differences in transplant outcome in cardiac transplant patients producing anti-donor HLA antibodies. The overall goals of this proposal are to elucidate whether the intracellular signaling events initiated by antibody ligation of class I and class II molecules are influenced by the specificity and concentration of the HLA antibody and to determine the clinical relevance of class I and II signaling pathways in cardiac transplantation. Patient samples to be used in the proposed research will be obtained from the "CTOT-05 Observational Study of Alloimmunity in Cardiac Transplant Recipients". The CTOT-05 study is a prospective, non-randomized, multicenter, observational clinical trial in cardiac transplant recipients. Under Aim 1, we will characterize the ability of anti-HLA class I and class II antibodies in sera from heart allograft recipients to mediate proliferative and/or cell survival signals in endothelial cells. The IgG fraction of the serum will be tested for its ability to transduce signals via MHC class I and class II molecules in donor and surrogate endothelial cells bearing the relevant HLA antigen(s). Under Aim 2 we will assess the expression of anti-HLA antibody induced protein phosphorylation, fibroblast growth factor receptors and anti-apoptotic proteins in clinical biopsy specimens from cardiac allografts with and without anti-HLA antibody production. Understanding the class I and class II signaling pathways in the context of antibody mediated rejection and transplant arteriosclerosis is of importance for the development of new diagnostic tools and therapeutic strategies to improve patient management and cardiac transplantation outcome. Relevance to Public Health: Studying anti-HLA antibody mediated signal transduction in samples from the CTOT-05 clinical trial will permit us to establish the importance of the class I and class II signaling pathways in cardiac transplant outcome. These studies will identify key signaling proteins mediating acute and chronic antibody-mediated rejection and may permit the development of new treatment strategies. This study will develop and test class I and class II antibody mediated signal transduction as reliable indicators of transplant outcome and provide insight into mechanisms underlying antibody mediated graft injury. (End of Abstract)