Impaired macrophage phagocytosis of bacteria in severe asthma

• Published in: Respiratory research Vol. 15; no. 1; p. 72
• Main Authors: Liang, Zhike, Zhang, Qingling, Thomas, Catherine MR, Chana, Kirandeep K, Gibeon, David, Barnes, Peter J, Chung, Kian Fan, Bhavsar, Pankaj K, Donnelly, Louise E
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 27.06.2014; BioMed Central
• Subjects: Adult; Asthma; Asthma - metabolism; Asthma - microbiology; Bacteria; Bacterial infections; Bronchoalveolar Lavage Fluid - microbiology; Chronic obstructive pulmonary disease; Comparative analysis; Complications and side effects; Development and progression; Drug therapy; Female; Haemophilus influenzae; Haemophilus influenzae - metabolism; Humans; Macrophages; Macrophages, Alveolar - metabolism; Macrophages, Alveolar - microbiology; Male; Medical research; Medicine, Experimental; Middle Aged; Patient outcomes; Phagocytosis - physiology; Physiological aspects; Severity of Illness Index; Staphylococcus aureus; Staphylococcus aureus - metabolism; Staphylococcus aureus infections; United Kingdom
• ISSN: 1465-993X; 1465-9921; 1465-993X
• DOI: 10.1186/1465-9921-15-72

Bacteria are frequently cultured from sputum samples of severe asthma patients suggesting a defect in bacterial clearance from the airway. We measured the capacity of macrophages from patients with asthma to phagocytose bacteria. Phagocytosis of fluorescently-labelled polystyrene beads, Haemophilus influenzae or Staphylococcus aureus by broncholaveolar lavage alveolar macrophages (AM) and by monocyte-derived macrophages (MDM) from non-asthmatics, mild-moderate and severe asthmatic patients was assessed using fluorimetry. There were no differences in phagocytosis of polystyrene beads by AMs or MDMs from any of the subject groups. There was reduced phagocytosis of Haemophilus influenzae and Staphylococcus aureus in MDMs from patients with severe asthma compared to non-severe asthma (p < 0.05 and p < 0.01, respectively) and healthy subjects (p < 0.01and p < 0.001, respectively). Phagocytosis of Haemophilus influenzae and Staphylococcus aureus by AM was also reduced in severe asthma compared to normal subjects (p < 0.05). Dexamethasone and formoterol did not suppress phagocytosis of bacteria by MDMs from any of the groups. Persistence of bacteria in the lower airways may result partly from a reduced phagocytic capacity of macrophages for bacteria. This may contribute to increased exacerbations, airway colonization and persistence of inflammation.