Qingxiang Liu,1,* Fei Peng,1,* Haitao Liu,2,* Qin Sun,1 Hui Chen,1 Xinyi Xu,1 Zihan Hu,1 Xing Zhou,1 Kai Jin,1 Jianfeng Xie,1 Yingzi Huang,1 Wei Huang,1 Yi Yang1 

1Jiangsu Provincial Key Laboratory of Critical Care Medicine, Department of Critical Care Medicine, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, 210009, People’s Republic of China; 2School of Life Science, Fudan University, Shanghai, 200000, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Wei Huang; Yi Yang, Email whuang@seu.edu.cn; yiyiyang2004@163.com

Background: Natural killer (NK) cells are key regulators of immune defense in sepsis-induced acute respiratory distress syndrome (ARDS), yet the characteristics of NK cell clusters in ARDS remain poorly understood.
Methods: A prospective and observational study enrolled septic patients with ARDS or not was conducted to determine the percentage of NK cells via flow cytometry. The transcriptomes of peripheral blood mononuclear cells (PBMCs) from healthy controls, patients with sepsis only, and patients with sepsis-induced ARDS were profiled. Vitro experiments were performed to confirm the mechanism mediating MX1+NK cell infiltration.
Results: A total of 115 septic patients were analyzed, among whom 63 patients developed ARDS and 52 patients did not. Decreased NK percentages were found in sepsis with ARDS patients (%, 7.46± 4.40 vs 11.65± 6.88, P=0.0001) compared with sepsis-only patients. A lower percentage of NK cells showed a significant increase in 28-day mortality. Single-cell sequencing analysis revealed distinct characteristics of NK cells in sepsis-induced ARDS, notably the identification of a unique cluster defined as MX1+NK cells. Flow cytometry analysis showed an elevated percentage of MX1+NK cells specifically in individuals with sepsis-induced ARDS, compared with patients with sepsis only. Pseudo-time analysis showed that MX1+NK cells were characterized by upregulation of type I interferon-induced genes and other pro-inflammatory genes. MX1+NK cells can respond to type I interferons and secrete type I interferons themselves. Ligand–receptor interaction analysis also revealed extensive interaction between MX1+NK cells and T/B cells, leading to an uncontrolled inflammatory response in ARDS.
Conclusion: MX1+NK cells can respond to type I interferons and secrete type I interferons themselves, promoting the development of sepsis-induced ARDS. Interfering with the infiltration of MX1+NK cells could be a therapeutic approach for this disease. Due to the limited sample size, a larger sample size was needed for further exploration.

Keywords: ARDS, inflammation, natural killer cells, sepsis