Molecular Basis of cDC1 Development

摘要 对肿瘤和许多病毒的初始适应性免疫应答依赖于CD 8 T细胞的启动，以产生 产生可以特异性靶向肿瘤或病毒感染细胞的细胞溶解效应T细胞。CD 8 T的启动 细胞与这些试剂的结合是通过特定类型的抗原呈递细胞在体内进行的，所述抗原呈递细胞是 骨髓系统和树突状细胞家族的成员。经典的树突状细胞（cDC）包括 几个密切相关的谱系，明显不同于其他骨髓细胞，如巨噬细胞，单核细胞， 细胞或粒细胞。首先，cDC用于激活T细胞对抗中枢淋巴组织中的感染。 而不是像其他骨髓谱系那样在感染部位直接发挥效应子功能。 cDC本身由至少两个主要分支组成，现在称为cDC 1和cDC 2。CDC1 是一个专门吸收和处理细胞相关抗原的谱系，例如来自肿瘤的抗原。 病毒感染的细胞和其细胞表面上的肽表位与MHC-I分子结合的表达， 克里斯这种形式的抗原：MHC-I复合物能够激活CD 8 T细胞，而不是CD 4 T细胞。这个过程是 称为交叉呈现。cDC 2不能在细胞内对病毒或肿瘤进行交叉呈递。 vivo. cDC 1与cDC 2具有许多遗传和分子差异; cDC 1需要一组不同的跨膜转运蛋白， 它们的发展不需要cDC 2的转录因子。这包括对trans-transmitting的依赖。 转录因子Nfil 3、Id 2、Irf 8和Batf 3。我们最近的研究表明，这些因素之间的遗传层次- tors具有Nfil 3作为第一个和起始因子，通过抑制 阻遏子Zeb 2。然而，Nfil 3是如何被诱导启动这一过程的，以及Nfil 3是如何工作以 抑制Zeb 2表达。最近，了解这些细节变得很重要，因为临床- 因此，我们有兴趣将Flt 3L施用用作扩大cDC 1体内群体的治疗剂。它有 一段时间以来，已知F13 L通常可以扩增树突状细胞，特别是扩增cDC 1。但 我们已经发现了一个令人惊讶和令人担忧的事实; Flt 3L给药将扩增cDC 1样细胞，即使在 Nfil 3缺陷小鼠，其预先完全缺乏cDC 1。cDC 1在Nfil 3缺陷小鼠中的扩增 Flt 3L产生的扩增与WT小鼠中的扩增具有相同的量级。因此，Flt 3L通过一种抑制剂诱导cDC 1。 与正常cDC 1发育不同的遗传途径。目前还没有测试这种cDC 1细胞是否 功能正常，并会增强免疫反应。本申请将系统地解决这一问题， 目的1）定义诱导NFIL 3的正常过程，目的2）定义诱导NFIL 3的机制， 目的3）确定Flt 3诱导的cDC 1功能是否正常，并确定 Flt 3L绕过cDC 1发育中Nfil 3正常需求的机制。

ABSTRACT The initial adaptive immune response to tumors and many viruses relies on the priming of CD8 T cells to gen- erate cytolytic effector T cells that can specifically target tumors or virally infected cells. The priming of CD8 T cells to these agents is carried out in vivo by a particular type of antigen presenting cell that is a component of the myeloid system and a member of the family of dendritic cells. Classical dendritic cells (cDCs) comprise several closely related lineages that are clearly distinct from other myeloid cells such as macrophages, mono- cytes or granulocytes. Primarily, cDCs serve to activate T cells against infections in the central lymphoid tis- sues, rather than carrying out direct effector functions at sites of infections as the other myeloid lineages do. The cDCs are themselves comprised of at least two major branches, now called cDC1 and cDC2. The cDC1 is a lineage that specializes in the uptake and processing of cell-associated antigens, such as from tumors of virally infected cells and the expression of peptide epitopes on its cell surface in conjunction with MHC-I mole- cules. This form of antigen:MHC-I complex is able to activate CD8 T cells, and not CD4 T cells. This process is called cross-presentation. The cDC2 is not capable of carrying out cross-presentation to viruses or tumors in vivo. The cDC1 has many genetic and molecular differences from cDC2; cDC1 require a distinct set of tran- scription factors for their development that are not required for cDC2. This includes dependence on the tran- scription factors Nfil3, Id2, Irf8 and Batf3. Our recent work showed that the genetic hierarchy among these fac- tors has Nfil3 as the first and initiating factor, acting to indirectly induce Id2 and Batf3 via the suppression of the repressor Zeb2. However, it is still unknown how Nfil3 is induced to initiate this process, and how Nfil3 works to suppress Zeb2 expression. It has recently become important to understand these details because of the clini- cal interest to apply Flt3L administration as a therapeutic in expanding the in vivo population of cDC1. It has been known for some time that Fl3L can expand dendritic cells in general and expand cDC1 in particular. But we have uncovered a surprising and worrisome fact; Flt3L administration will expand cDC1-like cells even in Nfil3-deficient mice, which completely lack cDC1 beforehand. The expansion of cDC1 in Nfil3-deficent mice produced by Flt3L is of the same magnitude as the expansion in WT mice. Thus, Flt3L is inducing cDC1 by a different genetic route than normal cDC1 development. There has been no test of whether such cDC1 cells function normally and will boost an immune response. This application will systematically address this issue by Aim 1) defining the normal process by which Nfil3 is induced, Aim 2) define the mechanism by which NFIL3 drives cDC1 development, and Aim 3) determine whether Flt3-induced cDC1 function normally and determine the mechanism by which Flt3L bypasses the normal requirement for Nfil3 in cDC1 development.