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

摘要 作为多功能、长寿记忆CD8 T细胞的标志，IL-2的产生能力被认为是 在效应性CD8T细胞中大量下调。使用区分效应器的新型表型标记 细胞毒性T淋巴细胞(CTL)进入记忆命中注定的(记忆前体效应细胞，MPEC)并最终 分化的(短命效应细胞，SLEC)亚群，我们的研究首次建立了记忆CD8 T细胞在分化过程中保持产生大量IL-2的能力；即使在效应期也是如此。 相位。我们发现，MPEC在产生效应器的同时，还能产生强劲的IL-2。 分子(颗粒酶B、干扰素-γ和肿瘤坏死因子-α)。这是令人惊讶的，因为幼稚的CD8 T细胞被认为在很大程度上 在激活和效应器分化后失去产生IL-2的能力。利用条件性脑损伤的小鼠模型 在抗原特异的CD8 T细胞亚群中，我们进一步发现自分泌IL-2是 在功能上相关，在主要反应期间(而不是在二次反应期间)需要，以印记 有效的记忆扩展和防止二次挑战的标志性记忆特性。 有趣的是，IL-2充足的MPEC转导旁分泌IL-2信号的效率低于它们的IL-2非分泌细胞. 生产SLEC对应物。SLEC不产生IL-2，但通过 高亲和力IL-2R的表达增强，扩增至MPECs的10倍以上。我们 假设MPECs自分泌IL-2信号与SLECs研究所强旁分泌IL-2信号有关 性质不同的基因表达程序，从而导致他们的生死命运截然不同。 或者，尽管MPEC保留了产生IL-2的能力，但实际上MPEC可能不会 在体内产生IL-2，因此经历了较小的扩张，并保留了他们的记忆适应性以供回忆 扩张。我们对IL-2在决定CD8T细胞命运中的作用的了解大多来自体外 评估MPECs和SLECs重新刺激后或通过基因消融IL-2产生IL-2的情况。 因此，能够产生IL-2的MPECs和不产生IL-2的SLECs的个体发育仍然不清楚。 他们体内产生IL-2的历史，并被胸腺发育效应或自身免疫混为一谈 生殖系IL2消融的副作用。在这个探索性的R21方案中，我们产生了独特的小鼠模型 有条件的IL-2基因缺失(用于特异性地消融胸腺后T细胞中的自分泌IL-2)，以及IL-2报告 系统(用于体内跟踪抗原特异性CD8T细胞产生IL-2的历史)。使用这些创新的 工具，我们试图解开自分泌和旁分泌IL-2信号如何决定极地生命的谜团 而不是MPEC和SLEC的死亡决定。信号和转录级联的照明 自分泌和旁分泌的下游IL-2信号可能被用于创新药理或药物 免疫干预，根据临床需要改变效应器和记忆性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.