Single-Cell Transcriptomics Reveals Macrophage Dysfunction and cDC2 Activation in COPD: Candidate Biomarkers for...

Chronic obstructive pulmonary disease (COPD) is a leading cause of global morbidity and mortality driven by dysregulated airway immunity. Macrophages and conventional type 2 dendritic cells (cDC2s) are central orchestrators of this process, yet their transcriptional heterogeneity at single-cell resolution and relationship to clinical severity remain incompletely characterized.

We performed integrative analysis of single-cell RNA sequencing (scRNA-seq) data from 45,708 lung immune cells combined with bulk microarray data from 236 lung tissue samples. After Harmony-based batch correction and graph-based clustering, 11 immune cell populations were annotated. Pseudobulk differential expression was performed using DESeq2, functional enrichment by gene set enrichment analysis against MSigDB Hallmark, KEGG, and GO:BP gene sets, and protein-protein interaction (PPI) network analysis using STRINGdb. Clinical correlation used Spearman rank correlation between hub gene expression and GOLD stage, FEV1% predicted, emphysema index, and DLCO%.

Macrophages were depleted in COPD while cDC2s were 4.7-fold expanded. Macrophages exhibited 1,268 differentially expressed genes dominated by IFN-γ response (NES = 2.60) and TNFα/NF-κB activation (NES = 2.41), with concurrent loss of mitochondrial function (NES = -2.40) and lysosomal acidification (NES = -2.25). cDC2s showed strong TNFα/NF-κB (NES = 2.88) and JAK-STAT (NES = 2.36) activation. PPI analysis identified IFNG, IL1B, CCR7, GZMB, and NFKB1 as central hubs. Cross-dataset validation confirmed LRG1, CCR7, IRF4, and TIMP1 as clinically correlated biomarkers.

This study identifies coordinated macrophage M1 polarization, metabolic dysfunction, and impaired efferocytosis in COPD, with cDC2-driven adaptive immune amplification. Eleven candidate biomarkers are proposed as targets for individualized nursing monitoring and precision respiratory care.