Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 04 26 1 16 Jianping Jiang Department of Respiratory Medicine, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China Shumin Li Department of Respiratory Medicine, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China Mengqing Cao Department of Respiratory Medicine, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China Haiqin Wang Department of Respiratory Medicine, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China Xiaoyan Jin Inpatient Service Center, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China 2025 08 20 2025 11 14 Bronchiectasis is a chronic respiratory condition characterized by persistent airway inflammation and recurrent infections, yet its underlying pathogenesis remains incompletely understood. This study aimed to investigate the roles of the lower respiratory tract microbiome and serum cytokine/chemokine profiles in the pathogenesis of bronchiectasis. In this retrospective study, we enrolled 285 bronchiectasis patients admitted to our hospital between January 2024 and June 2025. Participants were categorized into an acute exacerbation group (n=158) and a clinically stable group (n=127). We compared the two groups in terms of respiratory pathogens, immune function indicators (CD3+, CD4+, CD8+, CD4+/CD8+ ratio, white blood cell count, and neutrophil count), pro-inflammatory cytokines (interleukin-6, tumor necrosis factor-alpha, and interleukin-17A), anti-inflammatory cytokines (interleukin-10 and interleukin-4), acute-phase reactants (C-reactive protein, procalcitonin, and serum amyloid A), and chemokines (monocyte chemoattractant protein-1). The involvement of these factors in disease pathogenesis was analyzed. Significant differences were observed between the groups in the rates of hypoalbuminemia, the presence of dyspnea and hemoptysis, and the oxygenation index in arterial blood gas analysis. Sputum cultures were positive in 103 (65.19%) patients in the acute exacerbation group, compared to 58 (45.67%) in the stable group. Immune markers CD3+, CD4+, CD8+, and the CD4+/CD8+ ratio were lower during acute exacerbation, while WBC and NEUT levels were elevated. Pro-inflammatory cytokines (interleukin-6, tumor necrosis factor-alpha, and interleukin-17A) and acute-phase reactants (C-reactive protein, procalcitonin, and serum amyloid A) were significantly higher during exacerbation, whereas anti-inflammatory cytokines (interleukin-10 and interleukin-4) were lower. Monocyte chemoattractant protein-1 levels were also elevated during exacerbation. Dysbiosis of the lower respiratory tract microbiome, immune dysfunction, and exacerbated inflammatory responses are interrelated and collectively contribute to the pathogenesis of bronchiectasis. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4557 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4557/2330