Notch Signaling in Alloimmunity

摘要 针对外来宿主抗原的同种异体T细胞反应介导移植物抗宿主病，最大的 异基因造血细胞移植(allo-HCT)严重并发症在这个过程中 我们确定了Notch信号在致病同种异体T细胞调节中的关键作用 在多种allo-HCT小鼠模型中介导移植物抗宿主病(GVHD)。中的缺口抑制 捐献的T细胞可以长期预防移植物抗宿主病的发病率和死亡率。使用单抗， 我们确定了Notch1/2受体在T细胞中的关键作用和Delta-like 1/4(Dll1/4)Notch配体在T细胞中的关键作用 寄主，显性效应为Notch1和Dll4。出现短程抗体的DL1/4阻断 作为最有前景的针对Notch信号的策略，同时避免PAN-Notch的全身副作用 抑制力。我们最近发现了T细胞同种免疫中Notch调节的几个显著特征 这需要进一步调查。首先，我们鉴定了专门化的抗辐射基质细胞。 以Ccl19-Cre转基因作为次级淋巴器官Notch配体的关键来源 移植物抗宿主病的发病。这些发现揭示了成纤维细胞基质细胞亚群在移植物抗宿主病中的核心作用。第二, 在allo-HCT后几天内对Delta样Notch配体的短期抑制对于授予长期的 在多种小鼠模型中对移植物抗宿主病的长期保护。在这个早期的时间窗口内，Notch诱导了唯一的 同种异体抗原特异性T细胞激活过程中的转录效应 它们的差异性。第三，我们在非人类灵长类allo-hct模型中研究了Notch配体抑制。 模仿人类移植。单剂抗DLL4抗体具有显著的单剂活性 预防GVHD，显示从小鼠到非人类灵长类动物的Notch信号的高度保守的效果。在……里面 在这两个模型中，我们观察到肠道中调节性T细胞与常规T细胞的比率增加 预防肠道移植物抗宿主病，这是急性移植物抗宿主病最危险的组成部分。我们假设 同种异体抗原特异性T细胞与成纤维细胞基质细胞亚群的早期相互作用 表达Delta样Notch配体在T细胞中诱导Notch驱动的致病和肠道归巢程序 这促进了GVHD的发展。为了探索这一假设，我们将确定成纤维细胞基质的个别亚群。 在allo-HCT后早期将Dll1和/或Dll4Notch配体呈递给供者来源的T细胞的细胞，映射 支持同种异体反应性T细胞Notch激活的解剖位置，并定义免疫- 对次级淋巴器官中随后的基质网络的完整性进行中介损伤。此外, 我们将确定钝化Notch缺陷T细胞在肠道中积累的机制，从而防止 肠道GVHD，并研究Notch信号在同种异体反应性T细胞中的早期转录效应。 这些研究将为同种异体免疫的调节带来新的见解，并可能导致 限制同种异体移植后T细胞反应性的破坏性后果的新方法。

ABSTRACT Allogeneic T cell responses against foreign host antigens mediate graft-versus-host disease, the most serious complication of allogeneic hematopoietic cell transplantation (allo-HCT). During the course of this proposal we defined a critical role for Notch signaling in the regulation of pathogenic alloreactive T cells that mediate graft-versus-host disease (GVHD) in multiple mouse models of allo-HCT. Notch inhibition in donor T cells led to long-term protection from GVHD morbidity and mortality. Using monoclonal antibodies, we identified a critical role for Notch1/2 receptors in T cells and Delta-like1/4 (Dll1/4) Notch ligands in the host, with dominant effects of Notch1 and Dll4. Dll1/4 blockade with a short course of antibodies emerged as the most promising strategy to target Notch signaling while avoiding systemic side effects of pan-Notch inhibition. We recently uncovered several remarkable features of Notch regulation in T cell alloimmunity that warrant further investigation. First, we identified specialized radioresistant stromal cells lineage-traced with a Ccl19-Cre transgene as the critical source of Notch ligands in secondary lymphoid organs at the onset of GVHD. These findings uncover a central role for fibroblastic stromal cell subsets in GVHD. Second, short-term inhibition of Delta-like Notch ligands within days after allo-HCT was essential to confer long- term protection from GVHD in multiple mouse models. Within this early time window, Notch induced unique transcriptional effects during the activation of alloantigen-specific T cells that impacted selected aspects of their differentiation. Third, we studied Notch ligand inhibition in a non-human primate allo-HCT model that mimics human transplantation. A single dose of anti-DLL4 antibodies had marked single agent activity to prevent GVHD, showing highly conserved effects of Notch signaling from mice to non-human primates. In both models, we observed an increased ratio of regulatory to conventional T cells in the gut and striking protection from intestinal GVHD, the most dangerous component of acute GVHD. We hypothesize that alloantigen-specific T cells engage in early interactions with specialized subsets of fibroblastic stromal cells expressing Delta-like Notch ligands, inducing a Notch-driven pathogenic and gut-homing program in T cells that promotes GVHD. To explore this hypothesis, we will identify individual subsets of fibroblastic stromal cells that present Dll1 and/or Dll4 Notch ligands to donor-derived T cells early after allo-HCT, map the anatomical sites that support Notch activation in alloreactive T cells, and define the impact of immune- mediate injury on the subsequent integrity of stromal networks in secondary lymphoid organs. In addition, we will identify mechanisms that blunt the accumulation of Notch-deficient T cells in the gut, thus preventing intestinal GVHD, and investigate the early transcriptional effects of Notch signaling in alloreactive T cells. These studies will bring novel insights into the regulation of alloimmunity and might lead to the development of new approaches to limit damaging consequences of T cell reactivity after allogeneic transplantation.