Repeated sputum inductions induce a transient neutrophilic and eosinophilic response.
BACKGROUND
Sputum induction is a tool to monitor airway inflammation, yet it may induce by itself a neutrophilic response when repeated within 24 to 48 h. This limits its repeated use in clinical trials.


OBJECTIVE
We aimed to investigate the induction and resolution of inflammation generated by repeated sputum inductions.


METHODS
Sixteen healthy intermittent smokers participated in a study on the short-term effects of smoking. The nonsmoking arm consisted of seven successive sputum inductions with increasing time intervals (3, 6, 12, 24, 48, and 96 h). Inflammatory cellular characteristics and different soluble mediators were investigated.


RESULTS
The median percentage of sputum neutrophils increased significantly from baseline to 6 h (58.9% [range, 31.8 to 94.2%] to 83.2% [range, 26.7 to 98.3%], respectively). Surprisingly, the percentage of eosinophils also increased significantly from baseline to 6, 12, 24, and 48 h, as follows: 0.3% (range, 0.0 to 1.2%) to 1.7% (range, 0.0 to 15.5%), 2.2% (range, 0.5 to 12.5%), 1.2% (range, 0.0 to 4.8%), and 0.8% (range, 0.0 to 2.8%), respectively. Interleukin-8 increased significantly from baseline to 24 h (1,553 pg/mL [range, 462 to 8,192 pg/mL] to 2,178 pg/mL [range, 666 to 128,544 pg/mL]).


CONCLUSIONS
Repeated sputum inductions should preferably be avoided within 48 h. It induces not only a short-lived neutrophilic response but also a prolonged eosinophilic inflammatory response in healthy subjects, possibly by local changes in osmolarity, and subsequent epithelial and/or mast cell activation.
van der Vaart
Hester
H
University Medical Centre Groningen, Pulmonology, Hanzeplein 1, Groningen 9713 RB, the Netherlands.
Postma
Dirkje S
DS
Timens
Wim
W
Kauffman
Henk F
HF
Hylkema
Machteld N
MN
Ten Hacken
Nick H T
NH
D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis* / Q000276:immunology; D004802:Eosinophilia / Q000209:etiology*; D004804:Eosinophils / Q000276:immunology; D005260:Female; D005541:Forced Expiratory Volume / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000276:immunology*; D011653:Pulmonary Diffusing Capacity / Q000276:immunology; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000276:immunology; D012016:Reference Values; D012307:Risk Factors; D012462:Saline Solution, Hypertonic; D012907:Smoking / Q000009:adverse effects* / Q000276:immunology; D013183:Sputum / Q000276:immunology*; D014797:Vital Capacity / Q000276:immunology
D018836:Inflammation Mediators; D012462:Saline Solution, Hypertonic