| Summary: | Ravi Lokwani,1–3 Peter AB Wark,1–3 Katherine J Baines,1,3 Michael Fricker,1,3 Daniel Barker,3 Jodie L Simpson1–3 1Priority Research Centre for Healthy Lungs, Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia; 2Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton Heights, NSW 2305, Australia; 3School of Medicine and Public Health, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW 2308, AustraliaCorrespondence: Jodie L SimpsonLevel 2, East Wing, Hunter Medical Research Institute, Locked Bag, New Lambton 1000, NSW 2305, AustraliaTel +61 422220992Email jodie.simpson@newcastle.edu.auPurpose: To characterize neutrophils in obstructive airway disease by measuring their surface adhesion molecules and oxidative burst along with characterizing them into different subsets as per their adhesion molecule expression.Patients and methods: Peripheral blood from adults with COPD (n=17), asthma (n=20), and healthy participants (n=19) was examined for expression of CD16, CD62L, CD11b, CD11c, and CD54, and analyzed by flow cytometry. For oxidative burst and CD62L shedding analysis, CD16 and CD62L stained leukocytes were loaded with Dihydrorhodamine-123 (DHR-123) and stimulated with N-Formylmethionine-leucyl-phenylalanine (fMLF). Neutrophil subsets were characterized based on CD16 and CD62L expression. Marker surface expression was recorded on CD16+ neutrophils as median fluorescence intensity (MFI).Results: Neutrophil surface expression of CD62L was significantly reduced in COPD (median (IQR) MFI: 1156 (904, 1365)) compared with asthma (1865 (1157, 2408)) and healthy controls (2079 (1054, 2960)); p=0.028. COPD neutrophils also demonstrated a significant reduction in CD62L expression with and without fMLF stimulation. Asthma participants had a significantly increased proportion and number of CD62Lbright/CD16dim neutrophils (median: 5.4% and 0.14 × 109/L, respectively), in comparison with healthy (3.54% and 0.12 × 109/L, respectively); p<0.017.Conclusion: Reduced CD62L expression suggests blood neutrophils have undergone priming in COPD but not in asthma, which may be the result of systemic inflammation. The increased shedding of CD62L receptor by COPD blood neutrophils suggests a high sensitivity for activation.Keywords: COPD, asthma, neutrophils, adhesion molecules, neutrophils phenotype
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