Notch Signaling in Alloimmunity

Notch信号在同种免疫中的作用 同种异体T细胞对外来宿主抗原的应答介导了移植物抗宿主病， 异基因骨髓移植（allo-BMT）的严重并发症。在头五年 根据这一提议，我们定义了Notch信号在同种异体反应性T细胞介导的免疫应答中的新的关键作用。 异基因骨髓移植后移植物抗宿主病供体T细胞中经典Notch信号传导的抑制 在多种移植物抗宿主病小鼠模型中， 异基因骨髓移植Notch阻断诱导T细胞免疫调节的独特模式， 炎性细胞因子的产生和调节性T细胞的扩增增加。然而，在体内， T细胞增殖，淋巴造血器官中的扩增和细胞毒性在 切口抑制。T细胞中的Notch 1/2受体和宿主中的Delta样1/4（Dll 1/4）Notch配体 发挥了主导作用。Dll 1/4抑制作为抑制Notch信号传导的有希望的策略出现 而不诱导来自全身性泛Notch抑制的副作用。有趣的是，我们发现， 在移植前后短期抑制Dll 1/4足以提供长期保护 从发病率和死亡率。在allo-HCT后的前48小时内，Dll 1/4阻断是至关重要的， 有效地控制移植物抗宿主病，这表明Notch信号传导的关键早期脉冲是 它可以传递给传入的供体T细胞，对它们的致病功能产生持久的影响。 此外，我们在次级淋巴器官中鉴定了专门的抗辐射基质细胞， Dll 1/4 Notch配体在致死辐射和allo-BMT后的关键来源。我们假设 同种异体抗原特异性T细胞与非造血基质细胞亚群形成早期接触 在移植物抗宿主病中驱动T细胞致病性的次级淋巴器官中的细胞 通过Dll 1/4介导的Notch信号。为了详细探讨这一假设，我们将研究 Dll 1/4表达细胞的分布，并测试确定的Notch细胞来源的重要性 主要或次要同种异体抗原驱动的移植物抗宿主病多种模型中的配体 错配，并与梯度剂量的辐射;可视化和定义的同种异体抗原的相互作用， 次级淋巴器官中具有同种异体抗原和Notch配体的细胞来源的特异性T细胞; 并探讨Notch在同种异体反应性T细胞中作用的细胞和分子机制， 体内Notch敏感性的初始窗口。这些研究将带来新的见解， 调节同种免疫，并可能导致新方法的发展，以限制损害 同种异体移植后T细胞反应性的后果。

ABSTRACT Notch signaling in alloimmunity Allogeneic T cell responses against foreign host antigens mediate graft-versus-host disease, the most serious complication of allogeneic bone marrow transplantation (allo-BMT). During the first five years of this proposal, we defined a new critical role of Notch signaling in alloreactive T cells mediating graft-versus-host disease after allo-BMT. Inhibition of canonical Notch signaling in donor T cells markedly reduced the severity and mortality of graft-versus-host disease in multiple mouse models of allo-BMT. Notch blockade induced a unique pattern of immunomodulation in T cells, with decreased production of inflammatory cytokines and increased expansion or regulatory T cells. However, in vivo T cell proliferation, expansion in lympho-hematopoietic organs and cytotoxicity were preserved upon Notch inhibition. Notch1/2 receptors in T cells and Delta-like1/4 (Dll1/4) Notch ligands in the host played a dominant role. Dll1/4 inhibition emerged as a promising strategy to inhibit Notch signaling without inducing side effects from systemic pan-Notch inhibition. Interestingly, we discovered that short-term Dll1/4 inhibition in the peri-transplant period was sufficient to confer long-term protection from morbidity and mortality. Dll1/4 blockade during the first 48 hours after allo-HCT was essential to efficiently control graft-versus-host disease, suggesting that a critical early pulse of Notch signaling is delivered to incoming donor T cells, with a long-lasting impact on their pathogenic functions. Furthermore, we identified specialized radioresistant stromal cells in secondary lymphoid organs as the critical source of Dll1/4 Notch ligands after lethal irradiation and allo-BMT. We hypothesize that alloantigen-specific T cells form early contacts with resident subsets of non-hematopoietic stromal cells in secondary lymphoid organs that drive T cell pathogenicity in graft-versus-host disease through Dll1/4-mediated Notch signals. To explore this hypothesis in detail, we will investigate the distribution of Dll1/4-expressing cells and test the importance of defined cellular sources of Notch ligands in multiple models of graft-versus-host disease driven by major or minor alloantigen mismatches, and with graded doses of irradiation; visualize and define the interaction of alloantigen- specific T cells with cellular sources of alloantigens and Notch ligands in secondary lymphoid organs; and explore the cellular and molecular mechanisms of Notch action in alloreactive T cells during their initial window of Notch sensitivity in vivo. These studies will bring novel insights into the molecular regulation of alloimmunity and might lead to the development of new approaches to limit damaging consequences of T cell reactivity after allogeneic transplantation.