Introduction Bronchiectasis (BR) is a disease featuring a cycle of airway infection and inflammation, with the latter being driven by recruited neutrophils. Currently limited data is available comparing differences in biological function between healthy and BR patient derived neutrophils.

Aim To assess potential differences in peripheral blood neutrophil function between healthy individuals and BR patients.

Methods Neutrophils were isolated by gradient separation from whole blood samples from BR patients and healthy volunteers (not age matched). Four aspects of neutrophil biology were assessed in vitro: IL-8 secretion following stimulation with BR relevant stimuli (IL-8 ELISA, R and D systems), 24 hour viability (annexin V and propidium iodide staining), superoxide anion production (superoxide dependent cytochrome C reduction measurement) and phagocytosis rates (microscopic counts of neutrophils that had engulfed two or more zymosan particles).

Results Patients included those with BR alone and those with comorbid Rheumatoid arthritis (BROS). In all stimulatory conditions mean IL-8 secretion for healthy neutrophils (n=12) was lower than BR patient derived neutrophils (n=13), with the differences between the two groups being significant for unstimulated neutrophils and neutrophils stimulated by TNF-α, P. aeruginosa Whole cell lysates (WCLs) and H. influenzae WCLs (figure 1). Viability measured at regular 4 hour intervals across a 24 hour period showed a negative correlation in viability for both groups (n=3) but no significant difference in viability at any time point. Superoxide production was similar in both healthy (n=8) and BR (n=13) neutrophils, with 50 nM PMA yielding the highest increase in release for both healthy and BR patients (mean superoxide anion release of 14.2 nM and 14.3 nM respectively). 75.7% (95% CI: 71.5%–79.9%) of healthy neutrophils (n=6) phagocytosed 2 or more zymosan particles, BR patient (n=13) had a phagocytosis rate of 66.4% (95% CI: 64%–68.8%) which was significantly lower (p<0.001).

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Abstract S89 Figure 1

IL-8 Secretion by healthy and Bronchiectasis peripheral blood neutrophils following stimulation with disease relevant stimuli IL-8 secretion was higher in all conditions for bronchiectasis patient derived neutrophils, however only unstimulated neutrophils or neutrophils stimulated with TNF-α, 2.5% (v/v) P. aeruginosa WCLs or 2.5% (v/v) H. infleunzae WCLs showed a statistically significant difference between the two groups (±95% CI, **p<0.01, ***p<0.001)

Conclusion The superoxide production and 24 hour viability shows no difference between healthy and BR patients. Phagocytic ability and IL-8 secretion results suggest BR peripheral blood neutrophils had higher IL-8 secretion. There was a lower phagocytosis rate but this may not have reached a minimally clinically important difference.