Dysregulated NK Cell Activation and Myeloid-Lymphoid Imbalance Underpin COPD Progression: Insights from High-Dimensional Immune Profiling and Smoking-Induced Immune Remodeling

Background: Chronic obstructive pulmonary disease (COPD) is a significant global health concern, marked by persistent inflammation and immune dysregulation. Although it is widespread and has substantial clinical implications, the systemic immune mechanisms driving disease progression are not fully understood. Since blood contains a diverse array of immune cells and offers a non-invasive means of assessing immune homeostasis and overall physiological status, investigating immune dysregulation through blood sampling offers considerable value for both basic research and clinical application. This approach can provide novel insights into the pathogenesis of COPD. Methods: This study employed high-dimensional flow cytometry and RNA sequencing to comprehensively characterize peripheral immune cells from a cohort of 69 COPD patients spanning clinical stages 1 to 4, alongside 41 healthy donors as controls. To capture granulocyte populations typically excluded from peripheral blood mononuclear cell analyses, fresh whole blood samples were analyzed directly. Results: Our study revealed a marked shift in the myeloid-lymphoid balance, characterized by elevated neutrophils, eosinophils, and classical monocytes that correlated with disease severity, alongside reduced CD8? T cells and circulating T follicular helper cells. Transcriptional profiling identified oxidative stress pathways, T cell suppression, and aberrant natural killer (NK) cell activation as hallmarks of advanced COPD. Notably, activated Nkp44? NK cells were significantly enriched in severe stages, implicating their role in perpetuating inflammation. Smoking exacerbated immune perturbations, including upregulated complement activation and B cell pathways, though cessation partially restored transcriptional homeostasis. Conclusions: This study underscores the value of peripheral immune profiling in capturing the heterogeneity of COPD. The results reveal systemic immune dysregulation-especially NK cell hyperactivity and point to potential therapeutic avenues aimed at modulating immune responses to slow disease progression. Overall design: To elucidate the immune perturbations associated with COPD progression, we recruited 41 healthy donors and 69 patients with COPD spanning a spectrum of clinical severities: 19 with mild (stage 1), 26 with moderate (stage 2), and 24 with severe (stages 3-4) COPD. Flow-cytometric analysis was performed on all peripheral blood samples. To explore the transcriptomic changes underlying COPD pathogenesis, we randomly selected 35 of these samples for bulk RNA-seq: 10 from healthy donors and 25 from patients (stage 1, n = 6; stage 2, n = 12; stages 3–4, n = 7).