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Clinical & Experimental Allergy

Kinetics of pulmonary neutrophil recruitment and clearance in a natural and spontaneously resolving model of airway inflammation

Authors

  • T. J. Brazil,

    1. Wellcome Trust Centre for Research in Comparative Respiratory Medicine, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, Scotland, UK,
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  • M. P. Dagleish,

    1. Wellcome Trust Centre for Research in Comparative Respiratory Medicine, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, Scotland, UK,
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  • B. C. McGorum,

    1. Wellcome Trust Centre for Research in Comparative Respiratory Medicine, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, Scotland, UK,
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  • P. M. Dixon,

    1. Wellcome Trust Centre for Research in Comparative Respiratory Medicine, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, Scotland, UK,
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  • C. Haslett,

    1. Respiratory Medicine Unit, Rayne Laboratory, Medical School, University of Edinburgh, Scotland, UK
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  • E. R. Chilvers

    1. Respiratory Medicine Division, Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's and Papworth Hospitals, Cambridge, UK
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E. R. Chilvers, Respiratory Medicine Division, Department of Medicine, University of Cambridge School of Clinical Medicine Box 157, Level 5, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK. E-mail: erc24@hermes.cam.ac.uk

Summary

Background Neutrophil apoptosis and phagocytic clearance have been proposed as key determinants affecting the resolution of airway inflammation.

Objective To determine the kinetics of neutrophil priming, recruitment, activation and subsequent clearance in a naturally occurring equine disease model of neutrophilic pulmonary inflammation.

Methods and Results A 5 h mouldy hay/straw challenge in hypersensitive horses induced transient pulmonary dysfunction lasting 4 days. At 24 h circulating neutrophils were primed and displayed delayed rates of spontaneous apoptosis in vitro. Neutrophil numbers in the airspaces peaked at 5 h and then fell abruptly, returning to pre-challenge levels by 4 days. Airspace neutrophils demonstrated increased respiratory burst activity compared with circulating cells and equine neutrophil elastase 2A concentrations increased in parallel with neutrophil numbers indicating in vivo priming and degranulation. The number of apoptotic neutrophils and proportion of alveolar macrophages containing phagocytosed apoptotic neutrophils increased significantly at 24 h and 4 days post-challenge corresponding to the period of most rapid neutrophil clearance.

Conclusion This is the first demonstration of spontaneous neutrophil apoptosis and phagocytic removal in a natural disease model of airway inflammation and provides critical kinetic data to support the hypothesis that this clearance pathway plays a central role in the resolution of neutrophilic inflammation.

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