Increased neutrophils and cytokines, TNF-α and IL-8, in induced sputum of non-asthmatic patients with chronic dry cough
- Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Medicine & Royal Brompton Hospital, London SW3 6LY, UK
- Professor K F Chung.
- Received 24 June 1998
- Revision requested 1 September 1998
- Revised 7 October 1998
- Accepted 12 November 1998
Abstract
BACKGROUND The pathogenesis of non-asthmatic chronic dry cough remains unclear.
METHODS A study was undertaken to determine whether airway inflammation could be a contributing factor by analysing inflammatory cells and cytokines in induced sputum from 19 patients with chronic dry cough of varying aetiology, excluding asthma and bronchiectasis, and from 10 normal controls. The associated causes for the chronic cough were post-nasal drip (n = 5), gastro-oesophageal reflux (n = 4), and idiopathic (n = 10). All patients had an enhanced cough reflex to capsaicin.
RESULTS Sputum neutrophilia (median (interquartile range)) was found in the patients with chronic cough (59.4 (27.1)%) compared with the normal controls (28.4 (22.0)%; p<0.01, 95% CI 11.3 to 42.2). Sputum levels of interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α) were also significantly increased compared with normal controls (0.57 (1.08) and 0.25 (0.72) ng/ml; p<0.05 (95% CI 0.05 to 1.75) for IL-8; 48.3 (34.4) and 12.6 (33.6) pg/ml, p<0.01 (95% CI 8.8 to 69.8) for TNF-α).
CONCLUSION Neutrophils and cytokines associated with neutrophil chemotaxis and activation may contribute to the pathogenesis of non-asthmatic chronic dry cough.
