Mechanisms of alloantibody production following renal transplantation

摘要 急性和慢性抗体介导的排斥反应（AMR）是对移植物存活和功能的严重威胁。 移植器官目前AMR预防和治疗的选择受到不完整的 了解供体特异性同种抗体（DSA）产生和致病的机制 功能协调发展的而高亲和力同种型转换DSA的产生通常与锗酸盐有关， 滤泡B细胞的中心形成，边缘区（MZ）B细胞对抗供体反应的贡献 移植后的问题以前没有得到解决。我们的初步研究将MZ B细胞鉴定为 重要的参与者在协调DSA反应，并保证详细调查这B细胞亚群与 最终目的是降低移植受者的体液同种异体免疫。 供者同种异体移植物长期冷缺血保存（CIS）和随后的缺血/再灌注损伤（IRI）仍然存在 是导致移植结果不佳的主要风险因素之一。使用肾移植的小鼠模型， 同种异体移植物进行6小时CIS，我们发现移植后炎症特异性地增加生成， II类反应性DSA介导的移植物肾小球损伤。这些发现与临床高度相关。 研究揭示了较长的冷缺血时间、抗II类DSA和肾脏中晚期AMR之间的相关性， 移植患者然而，移植后炎症影响细胞生成的机制， 致病性II类DSA和用于B细胞活化的供体II类抗原的真正来源还不清楚。 根据我们的初步数据，我们假设IRI通过以下方式放大II类DSA的产生 步骤：1）IRI上调供体内皮细胞（EC）上MHC II类分子的表达， 2）脾MZ B细胞快速获得循环EEV，产生早期的细胞外囊泡（EEV）， DSA并促进FO B细胞进一步产生DSA;和，3）除了供体同种异体抗原外，MZ B细胞 通过移植物衍生的EV所携带的DAMP以及IRI的全身效应来启动和增强活化。 因此，靶向MZ B细胞的运输、活化和功能将抑制致病性II类的产生 DSA对改善长期CIS患者移植肾预后的作用。我们将在三个方面来检验这个假设。 具体目标： 目标1。为了检测缺血/再灌注损伤（IRI）是否通过增强内皮细胞功能来增强II级DSA， 细胞外囊泡（EEV）的产生。目标二。为了检测MZ B细胞在肾移植后DSA产生中的作用， 移植目标3：探讨MZ B细胞在致病性II类DSA生成中的作用 移植肾长时间冷缺血保存后。 这些研究将填补目前对体液同种免疫反应的认识中的几个空白， 血管化器官移植，并确定潜在的治疗干预目标，以抑制抗体- 介导的排斥

ABSTRACT Acute and chronic antibody-mediated rejection (AMR) is a serious threat to the survival and function of transplanted organs. The current options for AMR prevention and treatment are limited by the incomplete understanding of the mechanisms underlying donor specific alloantibody (DSA) generation and pathogenic functions. Whereas the production of high affinity isotype-switched DSA is typically associated with germinal center formation by follicular B cells, the contribution of marginal zone (MZ) B cells to anti-donor responses following transplantation has not been previously addressed. Our preliminary studies identify MZ B cells as important players in orchestrating DSA responses and warrant detailed investigation of this B cell subset with an ultimate objective of reducing humoral alloimmunity in transplant recipients. Prolonged cold ischemia storage (CIS) of donor allografts and ensuing ischemia/reperfusion injury (IRI) remain among leading risk factors for poor transplant outcome. Using a mouse model of kidney transplantation in which allografts are subjected to 6 h CIS, we found that posttransplant inflammation specifically augments generation of class II-reactive DSA that mediate allograft glomerular injury. These findings are highly relevant to clinical studies revealing correlations between longer cold ischemia time, anti-class II DSA and late AMR in renal transplant patients. However, the mechanisms by which posttransplant inflammation affects generation of pathogenic class II DSA and the very source of donor class II antigens for B cell activation are poorly defined. Based on our preliminary data, we hypothesize that IRI amplifies class II DSA production through the following steps: 1) IRI up-regulates MHC class II expression on donor endothelial cells (EC) and EC release of class II containing extracellular vesicles (EEVs); 2) spleen MZ B cells rapidly acquire circulating EEVs, produce early DSA and facilitate further DSA production by FO B cells; and, 3) in addition to donor alloantigens, MZ B cell activation is initiated and enhanced by DAMPs carried by graft-derived EVs as well as by systemic effects of IRI. Therefore, targeting MZ B cell trafficking, activation and functions will inhibit generation of pathogenic class II DSA and improve outcome of renal allografts subjected to prolonged CIS. We will test this hypothesis in three Specific Aims: Aim 1. To test whether ischemia/reperfusion injury (IRI) augments class II DSA by enhancing endothelial extracellular vesicles (EEV) generation. Aim 2. To test the role of MZ B cells in DSA production following renal transplantation. Aim 3. To investigate the contribution of MZ B cells in the generation of pathogenic class II DSA after prolonged cold ischemia storage of renal allografts. The proposed studies will fill several gaps in current knowledge of humoral alloimmune responses to vascularized organ transplants and identify potential targets of therapeutic intervention to inhibit antibody- mediated rejection.