Regulation of CD8 T cell memory by autocrine IL-2

 描述(申请人提供)：白介素2(IL-2)，最初被确认为T细胞生长因子，可能是研究最多的细胞因子，但新的生理功能继续归因于它。除了在调节耐受性方面发挥关键作用外，IL-2信号在产生对病原体的功能性CD8T细胞记忆方面也是至关重要的。我们最近证明了IL-2在急性病毒感染期间平衡效应器和记忆反应中的关键作用。此外，与通常认为的效应器CD8 T细胞不产生IL-2相反，我们惊讶地发现，记忆命中注定的效应器细胞产生大量IL-2，并在效应器和记忆阶段保持这种能力。事实上，强大的IL-2产生是长寿多功能记忆细胞的一个特征，也是强大的二次扩张所必需的。在对自分泌IL-2信号的生理相关性最严格的测试之一中，我们过继地将相同数量的野生型和IL-2/抗原特异性CD8 T细胞转移到野生型受体中，并跟踪同一宿主内对急性感染的记忆分化。令人兴奋的是，我们发现，尽管处于所有其他造血细胞和非造血细胞以及一半抗原特异性CD8 T细胞能够产生自己的IL-2的环境中，但IL-2/记忆性CD8 T细胞在重新挑战时在安装强大的二次扩增方面受到了损害。这一R03提案试图进一步扩展这些有希望的初步观察，以深入了解自分泌IL-2信号何时调节二次扩张的主要CD8 T细胞的记忆特性，以及旁分泌IL-2来源如何参与。利用新的条件性IL-2基因敲除小鼠，我们将在CD8T细胞原代扩增(记忆特性被印记时)或二次扩增阶段(记忆细胞经历快速增殖爆发和效应器分化时)熄灭自分泌或旁分泌IL-2信号，以探索L-2信号的作用时间。我们将利用表型、功能和转录图谱研究来获得IL-2信号如何调节CTL免疫的分子洞察力。为了开发有效的疫苗和免疫策略来诱导保护性的、长寿的CD8 T细胞免疫记忆，重要的是了解记忆CD8 T细胞为什么会产生自己的IL-2，这是何时以及如何调节记忆特性的，以及是否可以通过反式提供IL-2信号来实现最佳记忆反应。此外，这些研究为未来的R01建议奠定了发展基础-缩小自分泌IL-2信号的作用时间框架，以及清楚地识别所涉及的广泛的细胞和分子网络，将有助于我们在R01资助机制的支持下，适当地将我们未来的机制研究集中在自分泌IL-2调控的基因调控网络上。

 DESCRIPTION (provided by applicant): Interleukin-2 (IL-2), originally identified as a T-cell growth factor, is possibly the most studied cytokine, yet newer physiologic functions continue to be ascribed to it. In addition to its pivotal role in regulating tolerance, IL-2 signals are criticl for generating functional CD8 T cell memory to pathogens. We recently demonstrated a critical role of IL-2 in balancing effector and memory responses during acute viral infections. Moreover, contrary to common belief that effector CD8 T cells do not produce IL-2, in a surprise finding we discovered that memory-fated effector cells produce large amounts of IL-2 and retain this ability throughout effector and memory stages. Indeed, robust IL-2 production is a hallmark property of long-lived polyfunctional memory cells and is required for robust secondary expansion. In one of the most stringent tests for physiological relevance of autocrine IL-2 signals, we adoptively transferred equal numbers of wild-type and IL-2-/- antigen-specific CD8 T cells into wild-type recipients, and followed memory differentiation within the same host in response to acute infection. Excitingly, we found that despite being in an environment where all other hematopoietic and nonhematopoietic cells and half of the antigen-specific CD8 T cells were capable of producing their own IL-2, IL-2-/- memory CD8 T cells were compromised in mounting robust secondary expansion upon rechallenge. This focused R03 proposal seeks to further extend these promising preliminary observations towards gaining insight into when autocrine IL-2 signals regulate cardinal CD8 T cell memory property of secondary expansion, and how paracrine IL-2 sources participate. Using novel conditional IL-2 knockout mice, we will extinguish autocrine or paracrine IL-2 signals either during primary CD8 T cell expansion (when memory properties are imprinted), or during secondary expansion phases (when memory cells undergo rapid proliferative burst and effector differentiation) to explore the timing of action of L-2 signals. We will employ phenotypic, functional and transcriptional profiling studies to gain molecular insight into how IL-2 signals regulate CTL immunity. For development of efficacious vaccines and immunization strategies that induce protective, long-lived CD8 T cell immunological memory, it is important to know why memory CD8 T cells produce their own IL-2, when and how this regulates memory properties and whether IL-2 signals can be provided in trans for optimal memory responses. Moreover, these studies lay the developmental groundwork for a future R01 proposal - narrowing down the time frame of action of autocrine IL-2 signals and a clear identification of the broad cellular and molecular networks involved will help us appropriately focus our future mechanistic investigations of autocrine IL-2 regulated gene regulatory networks under the auspice of a R01 funding mechanism.