The signaling adapter MyD88 is critical for immune cell activation in response to viral or bacterial pathogens via several TLRs, IL-1βR and IL-18R. However, the essential role of MyD88 during activations mediated by germline-encoded NK cell receptors (NKRs), such as Ly49H or NKG2D, has yet to be investigated. To define the NK cell-intrinsic function of MyD88, we generated a novel NK cell conditional knockout mouse for MyD88 (Myd88^fl/flNcr1^Cre/+). Phenotypic characterization of these mice demonstrated that MyD88 is dispensable for NK cell development and maturation. However, the MyD88-deficient NK cells exhibited significantly reduced cytotoxic potentials in vivo. In addition, the lack of MyD88 significantly reduced the NKG2D-mediated inflammatory cytokine production in vitro. Consistent with this, mice lacking MyD88 were unable to respond and clear MCMV infection. Transcriptomic analyses of splenic NK cells following MCMV infection revealed that inflammatory gene signatures were upregulated in Ly49H⁺. In contrast, Ly49H⁻ NK cells have significant enrichment in G2M checkpoint genes, revealing distinct transcriptomic profiles of these subsets. Our results identify a central role for MyD88 in Ly49H-dependent gene signatures, including alterations in genes regulating proliferation in Ly49H⁺ NK cells. In summary, our study reveals a previously unknown function of MyD88 in Ly49H-dependent signaling and in vivo functions of NK cells.

信号转导接头 MyD88 对于免疫细胞通过几种 TLR、IL-1βR 和 IL-18R 对病毒或细菌病原体的反应至关重要。然而，MyD88 在由种系编码的 NK 细胞受体 (NKR)（如 Ly49H 或 NKG2D）介导的激活过程中的重要作用尚待研究。为了定义 MyD88 的 NK 细胞内在功能，我们为 MyD88 ( Myd88 ^fl/fl Ncr1 ^Cre/+ ) 生成了一种新的 NK 细胞条件性敲除小鼠。这些小鼠的表型特征表明，MyD88 对于 NK 细胞的发育和成熟是可有可无的。然而，MyD88 缺陷型 NK 细胞在体内表现出显着降低的细胞毒性潜力。此外，MyD88 的缺乏显着降低了体外NKG2D 介导的炎性细胞因子的产生。与此一致，缺乏 MyD88 的小鼠无法响应和清除 MCMV 感染。MCMV 感染后脾脏 NK 细胞的转录组学分析显示炎症基因特征在 Ly49H ⁺中上调。相比之下，Ly49H ^- NK 细胞在 G2M 检查点基因中具有显着富集，揭示了这些亚群的不同转录组谱。我们的研究结果确定了 MyD88 在 Ly49H 依赖性基因特征中的核心作用，包括调节 Ly49H ^{+增殖的基因改变}NK细胞。总之，我们的研究揭示了 MyD88 在 Ly49H 依赖性信号传导和NK 细胞的体内功能中以前未知的功能。