R848/TLR7 介导的更强的 CD8+ T 免疫依赖于 DC-NK 细胞相互作用。
R848/TLR7-Mediated Stronger CD8+ T Immunity Is Dependent on DC-NK Cell Interactions.
机构信息
Respiratory Medicine Department, The First Affiliated Hospital of Chongqing Medical University, Chongqing Medical University, Chongqing, China.
Integrated Medical Science Department, Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, USA.
出版信息
Int Arch Allergy Immunol. 2022;183(8):860-875. doi: 10.1159/000522364. Epub 2022 Mar 9.
BACKGROUND
Toll-like receptor (TLR) 7 agonists are effective candidates for Th1 immune adjuvants, which compensate for the insufficient Th1 immune responses induced by traditional adjuvants. This effect is currently dependent on TLR7-mediated induction of dendritic cell (DC) maturation and increased IL-12 production.
METHODS
In vivo, we intraperitoneally injected TLR agonists with OVA, and LNs were collected for detection. In vitro, Activated DCs, natural killer (NK) cells, and CD8+ T cells were tested using flow cytometry for surface expression and enzyme-linked immunosorbent assay for cytokine production. NK cell migration was evaluated using transwell system. All experiments were performed in both C57BL/6 and BALB/C backgrounds.
RESULTS
Our findings revealed that the enhanced CD8+ T immunity characterized by CD8+ T accumulation, proliferation, and IFN-γ+CD8+ T induction induced by R848 was attributed to DC-dependent NK cell migration and DC-NK interactions. Our results demonstrated that R848 induced CD8+ T cell accumulation and IFN-γ+CD8+ T cells in lymph nodes (LNs) to a greater degree in vivo than TLR4 agonists (lipopolysaccharide) and TLR9 agonists (Class C CPG). R848-activated DCs enhanced CD8+ T cell proliferation and increased IFN-γ+CD8+ T cells with the assistance of NK cells. In contrast, depletion of NK cell decreased IFN-γ+CD8+ T cell production. Greater NK cell migration to LNs occurred in R848-immunized mice. A similar effect of R848 on NK cell migration was observed in an in vitro transwell study. When co-cultured, NK cells plus R848 could promote DCs maturation, and in turn, DCs in combination of R848 augmented NK cells activation. Further studies demonstrated that among several TLR agonists, R848 produced the largest amount of the chemokine CXCL9 from activated DCs, which is relevant to NK cell migration. CXCL9 blockade reduced the number of migrated NK cells, and the addition of CXCL9 increased the number of NK cells.
DISCUSSION
Taken together, R848-mediated stronger CD8+ T cell immunity does not depend on DC activation alone, rather that NK cells must also be considered. By increasing our immunological understanding of the effect of R848/TLR7, these findings provide a new perspective for applying R848 in future clinical studies.
背景
Toll 样受体（TLR）7 激动剂是 Th1 免疫佐剂的有效候选物，可弥补传统佐剂诱导的 Th1 免疫应答不足。这种效应目前依赖于 TLR7 介导的树突状细胞（DC）成熟和增加 IL-12 的产生。
方法
体内，我们用 TLR 激动剂 OVA 腹腔注射，收集 LNs 进行检测。体外，通过流式细胞术检测激活的 DC、自然杀伤（NK）细胞和 CD8+T 细胞的表面表达，通过酶联免疫吸附试验检测细胞因子的产生。使用 Transwell 系统评估 NK 细胞的迁移。所有实验均在 C57BL/6 和 BALB/C 背景下进行。
结果
我们的研究结果表明，R848 诱导的 CD8+T 免疫增强，表现为 CD8+T 细胞在体内的积累、增殖和 IFN-γ+CD8+T 诱导，这归因于 DC 依赖性 NK 细胞迁移和 DC-NK 相互作用。我们的结果表明，R848 在体内诱导 CD8+T 细胞在淋巴结（LN）中的积累和 IFN-γ+CD8+T 细胞的程度比 TLR4 激动剂（脂多糖）和 TLR9 激动剂（Class C CPG）更大。R848 激活的 DC 增强 CD8+T 细胞的增殖，并在 NK 细胞的辅助下增加 IFN-γ+CD8+T 细胞。相反，NK 细胞耗竭会减少 IFN-γ+CD8+T 细胞的产生。在 R848 免疫的小鼠中，观察到更大程度的 NK 细胞向 LN 的迁移。在体外 Transwell 研究中观察到 R848 对 NK 细胞迁移的类似作用。当共培养时，NK 细胞加 R848 可促进 DC 的成熟，反过来，R848 组合的 DC 增强 NK 细胞的激活。进一步的研究表明，在几种 TLR 激动剂中，R848 从激活的 DC 中产生了最大量的趋化因子 CXCL9，这与 NK 细胞的迁移有关。CXCL9 阻断减少了迁移的 NK 细胞的数量，而添加 CXCL9 增加了 NK 细胞的数量。
讨论
综上所述，R848 介导的更强的 CD8+T 细胞免疫作用不仅依赖于 DC 的激活，而且必须考虑 NK 细胞。通过增加我们对 R848/TLR7 效应的免疫学理解，这些发现为未来的临床研究中应用 R848 提供了新的视角。
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