Decay accelerating factor dependent inhibition of T cell immunity

摘要 衰变加速因子（DAF、CD55）是一种糖磷脂酰肌醇 (GPI) 连接的、细胞表面表达的 具有已知主要功能的蛋白质作为内在（在其表达的细胞表面上）调节剂 补体级联激活。我们等人发现 DAF 至关重要地调节 T 细胞免疫 通过局部调节补体激活来做出反应。我们还表明，在同源 T 细胞/APC 相互作用 表面 DAF 表达快速（数小时内）但短暂（24-48 小时）下调。我们 假设这种短暂的下调至关重要地允许局部补体激活以驱动诱导 效应 T 细胞 (Teff) 的同时抑制调节性 T 细胞的诱导、功能和稳定性 （特雷格）。虽然已生产出 DAF 缺陷动物并表现出增强的 T 细胞免疫反应， 对该假设的正式检验需要能够在免疫上持续执行稳定的 DAF 表达。 体内细胞表面。我们的假设预测这种强制的 DAF 表达将抑制 APC 激活并 限制 Teff 免疫的诱导，同时将允许和促进 Treg 诱导/稳定 抑制保护性抗病毒 T 细胞免疫，同时有利于针对同种异体或异体的免疫耐受 自身抗原。如果我们的工作模式是正确的，那么研究结果将在概念上具有创新性并具有重要意义 他们将支持一种在体内控制 T 细胞免疫的新机制。拟议的工作将 导致产生具有可诱导的、稳定的 DAF 表面表达形式的小鼠，从而添加 可用于研究适应性之间联系的生物试剂工具箱中缺少的重要工具 免疫和补体激活。我们建议通过 2 在此 R21 应用程序中测试这一假设 目标：1) 通过在造血细胞中强制表达 DAF 来调节 T 细胞免疫；2) 生产 并分析可诱导、条件性 DAF 转基因小鼠的 T 细胞免疫反应。结果得出 从这个“高风险高回报”的 R21 应用程序中可能会为 DAF 的影响提供新的见解 表达（而不是缺失）对体内 T 细胞免疫反应的影响，这一问题尚未得到解决 并代表了我们当前知识的空白。如果我们的工作模型是正确的，研究结果将提供 增加 DAF 表达以诱导耐受性反应的新治疗策略的基础 预防和/或治疗自身免疫性疾病、移植排斥和移植物抗宿主病。此外，在 完成 R21 拨款后，我们将生产出新型生物工具，包括诱导型 DAF 转基因小鼠将使我们能够测试自身免疫和移植中 DAF 依赖性耐受策略 模型，确定 DAF 是否以及如何影响初始和/或记忆 T 细胞激活的诱导，以及 在每种情况下发挥作用，并深入了解生理性 DAF 下调的机制。

Abstract Decay accelerating factor (DAF, CD55) is a glycophosphatidylinositol (GPI)-linked, cell surface-expressed protein with a known primary function as an intrinsic (on the cell surface on which it is expressed) regulator of complement cascade activation. We among others discovered that DAF crucially modulates T cell immune responses by locally regulating complement activation. We also showed that during cognate T cell/APC interactions surface DAF expression is rapidly (within hours) yet transiently (24-48h) downregulated. We hypothesize that this transient downregulation crucially permits local complement activation to drive induction of effector T cells (Teff) while simultaneously inhibiting induction, function and stability of regulatory T cells (Treg). While DAF deficient animals have been produced and exhibit enhanced T cell immune responses, formal testing of this hypothesis requires the ability to constitutively enforce stable DAF expression on immune cell surfaces in vivo. Our hypothesis predicts that this enforced DAF expression will inhibit APC activation and limit induction of Teff immunity and simultaneously will permit and facilitate Treg induction/stability, together dampening protective anti-viral T cell immunity while favoring immunological tolerance directed toward allo- or autoantigens. If our working model is correct, the findings will be conceptually innovative and significant in that they would support a novel mechanism that exerts control over T cell immunity in vivo. The proposed work will result in production of a mouse with an inducible, stable surface expressed form of DAF, thereby adding an essential missing tool to the toolbox of biological reagents available for studying links between adaptive immunity and complement activation. We propose to test this hypothesis in this R21 application through 2 aims: 1) To modulate T cell immunity by enforced DAF expression in hematopoietic cells and 2) To produce and analyze T cell immune responses in an inducible, conditional, DAF transgenic mouse. The findings derived from this “high-risk high-reward” R21 application are likely to provide new insight into the impact of DAF expression (rather than its absence) on in vivo T cell immune responses, an issue that has not been addressed and represents a gap in our current knowledge. If our working model is correct, the findings would provide the basis for novel therapeutic strategies to increase DAF expression in efforts to induce tolerogenic responses that prevent and/or treat autoimmune disease, transplant rejection and graft vs. host disease. In addition, at the completion of this R21 grant we will have produced novel biological tools including inducible DAF transgenic mice that will permit us to test DAF-dependent tolerogenic strategies in autoimmune and transplant models, determine whether and how DAF impacts induction of naïve and/or memory T cell activation and function in each situation, and provide insight into mechanisms underlying physiological DAF downregulation.