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Blood Neutrophils are Reprogrammed in Bronchiectasis

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Original languageEnglish
JournalAmerican Journal of Respiratory and Critical Care Medicine
Volume198
Issue number7
Early online date7 May 2018
DOIs
Publication statusPublished - 1 Oct 2018

Abstract

Introduction
Excessive neutrophilic airways inflammation is the central feature of bronchiectasis, but little is known about neutrophils in bronchiectasis. The aim of this study was to assess blood neutrophil phenotype in bronchiectasis patients both whilst stable and during exacerbations.

Methods
In the clinically-stable arm of this study were 8 healthy volunteers, 8 mild and 8 severe bronchiectasis. In addition, 6 severe bronchiectasis patients were compared with 6 community-acquired pneumonia patients at the start and end of an exacerbation. We assessed neutrophils for spontaneous apoptosis rate, cell surface marker expression, degranulation, reactive oxygen species generation, phagocytosis and killing of Pseudomonas aeruginosa (PAO1). In addition, blood neutrophil function was compared to airway neutrophil function in bronchiectasis.

Results
In stable bronchiectasis, compared to healthy volunteers, blood neutrophils had: significantly prolonged viability; delayed apoptosis; increased CD62L shedding; upregulated CD11b expression; increased myeloperoxidase release; impaired neutrophil phagocytosis and killing of PAO1.

Bronchiectatic airway neutrophils had significantly lower bacterial phagocytosis and killing, than their matched autologous blood neutrophils. Both blood and airway neutrophil phagocytosis and killing was impaired at the start of an exacerbation and improved following antibiotic treatment.

In pneumonia patients, there was a significant improvement in phagocytosis and killing after treatment with antibiotics. On comparing phagocytosis and killing during exacerbations in bronchiectasis to pneumonia patients, there was no difference in phagocytosis, but there was significantly increased bacterial killing at the start and end of infection in pneumonia patients compared to bronchiectasis patients.

Conclusion
In the stable state, in bronchiectasis, peripheral blood neutrophils are reprogrammed and have prolonged survival.This impairs their functional ability of bacterial phagocytosis and killing, thereby perpetuating the vicious circle in bronchiectasis.


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