Antigen challenge increases adherence of circulating neutrophils in horses with chronic obstructive pulmonary disease.
Authors: Marr K A, Lees P, Cunningham F M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Antigen Challenge and Neutrophil Adhesion in Equine COPD Neutrophil accumulation in the airways is a hallmark of COPD pathology in horses, yet the mechanisms driving this recruitment remain incompletely understood. Marr and colleagues investigated whether antigen exposure triggers changes in circulating neutrophil adhesion properties that might facilitate airway infiltration, using an in vitro adhesion assay combined with experimental antigen challenge in susceptible and control horses. Within 24 hours of a 7-hour antigen challenge, unstimulated neutrophils from COPD-susceptible horses showed dramatic increases in adherence to protein-coated plastic (from approximately 3% to 20%), whilst neutrophils from healthy controls remained unchanged; critically, blocking the CD18 adhesion molecule with monoclonal antibody inhibited this increase by 96%, identifying the specific mechanism responsible. Parallel bronchoalveolar lavage sampling revealed neutrophil percentages surging from 1% to 80% in the respiratory tract, suggesting that systemically activated neutrophils are indeed preferentially recruited to inflamed airways. These findings indicate that antigen-induced neutrophil priming—mediated via CD18-dependent adhesion pathways—represents a tractable therapeutic target; interventions that limit circulating neutrophil activation or block CD18-mediated adhesion could potentially reduce the pathological neutrophilic airway infiltration that characterises COPD exacerbations in susceptible horses.
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Practical Takeaways
- •Antigen exposure in COPD-susceptible horses activates circulating neutrophils and increases their migration to airways; managing environmental antigen exposure may help reduce airway inflammation in affected horses
- •Blocking CD18 integrin markedly reduces antigen-induced neutrophil activation—this suggests potential therapeutic targets for treating or preventing COPD exacerbations
- •The dramatic increase in airway neutrophils (1% to 80%) following antigen challenge confirms that systemic neutrophil activation directly contributes to the pathophysiology of equine COPD
Key Findings
- •Antigen challenge increased neutrophil adherence in COPD-susceptible horses from 2.5-3.4% to 19.6-21.8% at 24 hours, while adherence remained unchanged in normal horses
- •Anti-CD18 monoclonal antibody H20A inhibited the antigen-induced increase in adherence by 96%
- •Neutrophil percentage in bronchoalveolar lavage fluid increased dramatically from 1% to 80% at 24 hours post-antigen challenge
- •No significant difference in neutrophil adherence to mediators (PAF, hrIL-8, hrC5a) was observed between COPD-susceptible and normal horses in unstimulated baseline conditions