Chronic obstructive pulmonary disease (COPD) is a major respiratory disease characterized by small airway inflammation, emphysema and severe breathing difficulties. Low-grade systemic inflammation is an established hallmark of severe disease, however, the molecular changes in peripheral immune cells remain far from understood. We combined multi-color flow cytometry with single-cell RNA sequencing and showed that blood neutrophil numbers are significantly increased in COPD and they are a heterogeneous population. A transcriptomic state that expressed interferon response genes correlated with alveolar damage and acute exacerbations. Furthermore, bronchoalveolar neutrophils expressed gene signatures corresponding to certain blood neutrophil states. Last, our data in a murine model of cigarette smoke exposure demonstrated that bone marrow neutrophil progenitors are expanded in smoke-treated animals and display signs of immune activation. Our study provides evidence that COPD systemic inflammation may derive from an activated haematopoietic precursor compartment.

Chronic obstructive pulmonary disease (COPD) is a major respiratory disease characterized by small airway inflammation, emphysema and severe breathing difficulties. Low-grade systemic inflammation is an established hallmark of severe disease, however, the molecular changes in peripheral immune cells remain far from understood. We combined multi-color flow cytometry with single-cell RNA sequencing and showed that blood neutrophil numbers are significantly increased in COPD and they are a heterogeneous population. A transcriptomic state that expressed interferon response genes correlated with alveolar damage and acute exacerbations. Furthermore, bronchoalveolar neutrophils expressed gene signatures corresponding to certain blood neutrophil states. Last, our data in a murine model of cigarette smoke exposure demonstrated that bone marrow neutrophil progenitors are expanded in smoke-treated animals and display signs of immune activation. Our study provides evidence that COPD systemic inflammation may derive from an activated haematopoietic precursor compartment.

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