LILRB1 Modulates Neutrophil Migration, NETosis, and Inflammation in Drug-Resistant Pseudomonas aeruginosa-Associated Bronchiectasis

Shaochu Zheng,1,* Shihao Yang,1,* Yuting Huang,1 Kangkang Hong,2 Jinling Tang,1 Xiaopu Wu,1 Cao Qing,1 Yun Jiang,1 Wei Lu,1 Chongxi Bao,1 Jing Luo,1 Jinliang Kong1 1Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, People’s Republic of China; 2Department of Geriatric Medicine, The Fourth Affiliated Hospital of Guangxi Medical University, Liuzhou, Guangxi, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jing Luo; Email [email protected] Jinliang Kong, Email [email protected]: Patients with drug-resistant Pseudomonas aeruginosa (P. aeruginosa)-associated bronchiectasis often exhibit persistent neutrophilic airway inflammation. The immunomodulatory receptor leukocyte immunoglobulin-like receptor B1 (LILRB1) is known to function as an inhibitory checkpoint in immune responses, yet its specific role in regulating neutrophil function in drug-resistant P. aeruginosa-associated bronchiectasis remains incompletely understood. This study aimed to characterize the function of LILRB1 in this clinical context.Methods: Clinical samples were obtained from bronchiectasis patients with drug-resistant P. aeruginosa infection and control subjects. LILRB1 mRNA expression was quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and soluble HLA-G (sHLA-G) levels were assessed by enzyme-linked immunosorbent assay (ELISA). Neutrophils isolated from peripheral blood were stimulated with a clinical isolate of drug-resistant P. aeruginosa. NETosis was evaluated using myeloperoxidase (MPO)/citrullinated histone H3 (CitH3) immunofluorescence staining and quantified via PicoGreen dsDNA assay. The modulatory effect of recombinant LILRB1 protein was examined in a Transwell co-culture system composed of neutrophils and P. aeruginosa-infected BEAS-2B bronchial epithelial cells, with neutrophil migration and inflammatory cytokine secretion assessed as outcome measures.Results: LILRB1 expression was significantly lower in patients with drug-resistant P. aeruginosa infection than in controls (P = 0.0384) and was inversely associated with disease severity, as indicated by the Bronchiectasis Severity Index (P = 0.0089), and with peripheral neutrophil counts (r = − 0.35, P = 0.044). Levels of sHLA-G in bronchoalveolar lavage fluid were elevated and showed an inverse correlation with LILRB1 expression. Treatment with recombinant LILRB1 protein significantly attenuated P. aeruginosa-induced neutrophil migration in the co-culture model, reducing the number of migrated cells from 4.43± 0.26× 104 to 2.75± 0.19× 104. Furthermore, LILRB1 protein suppressed NETosis and significantly decreased the concentrations of IL1β, IL6, and IL8 in the co-culture supernatants.Conclusion: Our findings indicate that LILRB1 acts as a significant regulator of neutrophilic inflammation in drug-resistant P. aeruginosa-associated bronchiectasis. By dampening neutrophil migration, NETosis, and pro-inflammatory cytokine release, LILRB1 may represent a potential target for mitigating inflammation in this patient population.Keywords: bronchiectasis, LILRB1, neutrophilic inflammation, HLA-G, Pseudomonas aeruginosa, drug-resistant