Exploring the thymic origin of group 2 innate lymphoid cells

摘要 先天淋巴细胞 (ILC) 在形成先天免疫和适应性免疫方面发挥着多种作用。这些细胞存在为 异质群体及其身份受到其组织环境的影响。同样， ILC 的个体发育也很复杂。尽管 ILC 被认为源自骨髓祖细胞或组织 驻留祖细胞在胚胎发生过程中分布，我们实验室的工作强烈表明，ILCs 胸腺中也可以产生至少 ILC2，不仅来自多能祖细胞，还来自 定型T细胞前体。我们最近使用单细胞 RNA 测序获得的数据表明，大量 野生型小鼠 (WT) 血液中富含 ILC 的群体的一部分来自胸腺，并且它们的 在外周组织中也可以找到等同物。因此，我们假设胸腺输出一种 大量 ILC 前体进入循环，可补充 ILC2 和/或其他 ILC 在稳态或免疫挑战时的外周组织中，胸腺来源的 ILC 可能 具有不同的功能。在这个更新提案中，我们打算跟进这些令人兴奋的新发现，并 确定这些胸腺来源的 ILC 前体的功能及其生物学意义。我们将进一步 描述肺和小肠中胸腺来源的 ILC 前体的特征并确定它们的频率 在小鼠发育过程中。我们还将鉴定人血液中胸腺衍生的 ILC 前体，从而获得 评估这些细胞的临床相关性。接下来我们就重点学习这些的功能 使用体外和体内方法以及纯化的过继转移胸腺衍生的ILC前体 ILC 前体转化为缺乏 ILC 的 Rag2-/-Il2g-/- 小鼠。这些细胞在 2 型免疫中的行为 反应将受到监测。最后，我们将评估 WT ILC2 之间的细胞内在功能差异 由骨髓共同淋巴祖细胞 (CLP) 和胸腺 DN1 和 DN3 T 细胞前体产生。 总而言之，本提案中概述的研究将进一步加深我们对胸腺来源的 ILC 的理解， 将有助于建立有关 ILC 池的生产和维护的新范例。因为 活跃胸腺的存在是儿童和成人之间的主要区别之一，知识 关于胸腺来源的 ILC 的研究可能有助于揭示它们不同的免疫反应，例如 Covid-19 期间的免疫反应 感染。

Abstract Innate lymphoid cells (ILCs) play diverse roles in shaping innate and adaptive immunity. These cells exist as heterogeneous populations and their identities are influenced by their tissue environments. Likewise, the ontogeny of ILCs is also complex. Although ILCs are thought to arise from bone marrow progenitors or tissue resident progenitors distributed during embryogenesis, work from our laboratory strongly suggest that ILCs at least ILC2s can also be generated in the thymus, not only from multipotent progenitors but also from committed T cell precursors. Our recent data using single cell RNA sequencing suggest that a substantial fraction of the ILC-enriched population in the blood of wild type mice (WT) come from the thymus, and their equivalents can also be found in peripheral tissues. We thus hypothesize that the thymus exports a substantial amount of ILC precursors to the circulation, which may replenish ILC2s and/or other ILCs in peripheral tissues in steady-state or upon immune challenges and the thymus-derived ILCs may have distinct functions. In this renewal proposal, we intend to follow up on these new exciting findings and determine the function of these thymus-derived ILC precursors and their biological significant. We will further characterize thymus-derived ILC-precursors in the lung and small intestine and determine their frequencies during mouse development. We will also identify thymus-derived ILC precursors in human blood, thus gaining appreciation of the clinical relevance of these cells. We will then focus on learning the function of these thymus-derived ILC precursors using in vitro and in vivo approaches, as well as adoptive transfer of purified ILC precursors into Rag2-/-Il2g-/- mice which are devoid of ILCs. The behaviors of these cells in type 2 immune reactions will be monitored. Finally, we will assess the cell-intrinsic functional differences among WT ILC2s generated from bone marrow common lymphoid progenitors (CLP) and thymic DN1 and DN3 T cell precursors. Taken together, studies outlined in this proposal will further our understanding of thymus-derived ILCs, which will help establish a new paradigm regarding to the production and maintenance of ILC pools. Because the presence of an active thymus represents one of the major differences between children and adults, knowledge about thymus-derived ILCs may shed light on their different immune responses such as those during Covid-19 infection.