Differential IL-2 Expression by Effector CD8 T cells and Fate Determination

摘要 多功能、长寿命记忆性CD 8 T细胞的标志，IL-2产生能力被认为是 在效应CD 8 T细胞中大量下调。使用区分效应子的新型表型标记 细胞毒性T淋巴细胞（CTL）进入记忆命运（记忆前体效应细胞，MPEC），并最终 分化的（短寿命效应细胞，SLEC）亚群，我们的研究是第一个建立记忆CD 8 T细胞在整个分化过程中保持产生大量IL-2的能力;即使在效应细胞分化期间， 相位我们发现MPECs能够产生大量的IL-2，同时也能产生大量的效应物。 分子（颗粒酶B、IFN-γ和TNF-α）。这是令人惊讶的，因为幼稚的CD 8 T细胞被认为在很大程度上是 在活化和效应分化后丧失IL-2产生能力。使用小鼠模型， 通过在抗原特异性CD 8 T细胞亚群中进行IL-2消除，我们进一步发现自分泌IL-2是 功能相关，并且在主要响应期间（而不是在次要响应期间）需要 记忆的标志性特性，即有效的回忆扩展和对二次挑战的保护。 有趣的是，IL-2-充足的MPEC抑制旁分泌IL-2信号的效率低于它们的IL-2-不充足的MPEC。 生产SLEC对应物。SLEC不产生IL-2，但通过受体接收强旁分泌IL-2信号 增加高亲和力IL-2 R的表达，并扩增至比MPEC高约10倍的数量。我们 假设MPEC中自分泌IL-2信号传导与SLECs中强旁分泌IL-2信号传导 在性质上不同的基因表达程序，从而导致他们完全不同的生活与死亡的命运。 或者，可能的是，尽管保留了产生IL-2的能力，但MPEC实际上不 在体内产生IL-2，因此经历较少的扩张，并保留其记忆适应性以供回忆 扩张.我们对IL-2在CD 8 T细胞命运决定中的作用的大部分理解来自于体外实验， 评估MPEC和SLEC再刺激后或通过IL-2的遗传消除的IL-2产生。 因此，具有IL-2产生能力的MPEC和不产生IL-2的SLEC的个体发育仍然不清楚维斯 a维斯于其体内IL-2产生的历史，并且被胸腺发育效应或自身免疫性 生殖系IL 2消融的副作用。在这个探索性的R21提案中，我们已经产生了独特的小鼠模型 条件性il 2基因缺失（用于特异性消除胸腺后T细胞中的自分泌IL-2），和IL-2报告基因 系统（用于体内追踪抗原特异性CD 8 T细胞的IL-2产生历史）。利用这些创新 工具，我们试图解决自分泌和旁分泌IL-2信号如何决定极地生活的谜团 对比MPEC和SLEC的死亡决定。信号传导和转录级联的阐明 自分泌和旁分泌IL-2信号的下游可用于创新新的药理学或 免疫干预，以改变临床需求所定义的效应和记忆CTL的平衡。

ABSTRACT A signature of polyfunctional, long-lived memory CD8 T cells, IL-2 production capability is believed to be largely downregulated in effector CD8 T cells. Using novel phenotypic markers that distinguish effector cytotoxic T lymphocytes (CTLs) into memory-fated (memory precursor effector cell, MPEC) and terminally differentiated (short-lived effector cell, SLEC) subsets, our studies were the first to establish that memory CD8 T cells retain the ability to produce copious amounts of IL-2 throughout differentiation; even during the effector phase. We found that MPECs are capable of robust IL-2 production alongside vigorous production of effector molecules (granzyme B, IFN-γ and TNF-α). This was surprising since naïve CD8 T cells are believed to largely lose IL-2 production capability after activation and effector differentiation. Using murine models of conditional il2 ablation in a subset of antigen-specific CD8 T cells, we have further discovered that autocrine IL-2 is functionally relevant, and is needed during primary responses (and not during secondary responses) to imprint the hallmark memory property of potent recall expansion and protection against secondary challenge. Intriguingly, IL-2-sufficient MPECs transduce paracrine IL-2 signals less efficiently than their IL-2 non- producing SLEC counterparts. SLECs do not make IL-2, but receive strong paracrine IL-2 signals through increased expression of the high affinity IL-2R, and expand to ~10-fold higher numbers than MPECs. We hypothesize that autocrine IL-2 signaling in MPECs versus strong paracrine IL-2 signals in SLECs institute qualitatively distinct gene expression programs, thus resulting in their starkly disparate life versus death fates. Alternatively, it is possible that despite retaining the ability for IL-2 production, MPECs in actuality do not produce IL-2 in vivo, thus undergoing lesser expansion and preserving their memory fitness for recall expansion. Much of our understanding of the role of IL-2 in CD8 T cell fate determination comes from in vitro assessment of IL-2 production after restimulation of MPECs and SLECs, or through genetic ablation of IL-2. Hence, the ontogeny of IL-2 production capable MPECs and IL-2 non-producing SLECs remains ill-defined vis a vis their history of in vivo IL-2 production, and is confounded by thymic developmental effects or autoimmune side effects of germline il2 ablation. In this exploratory R21 proposal we have generated unique murine models of conditional il2 gene deletion (for specific ablation of autocrine IL-2 in post-thymic T cells), and IL-2 reporter system (for in vivo tracking of IL-2 production history of antigen-specific CD8 T cells). Using these innovative tools, we seek to resolve the enigma of how autocrine and paracrine IL-2 signals determine the polar life versus death decisions of MPECs and SLECs. Illumination of the signaling and transcriptional cascades downstream of autocrine and paracrine IL-2 signals may be exploited for innovating novel pharmacologic or immunologic interventions to shift the balance of effector and memory CTLs as defined by clinical needs.