Circulatory neutrophils in COPD feature downregulated CD62L expression in comparison with asthma and healthy participants

Introduction: The regulation of adhesion molecules present on the surface of neutrophils plays an important role in their influx to the airways during inflammation. The pattern of this regulation and its association with neutrophil function is not well known in obstructive airway disease (OAD) and understanding these patterns may provide insight into neutrophil activation and recruitment to the airways. Aim: To measure blood neutrophil adhesion molecule (CD62L, CD11b, CD11c, CD54) surface expression in OAD and healthy participants. Methods: Peripheral, whole blood from 20 asthma, 16 COPD and 20 healthy participants was incubated with CD16-PE-Cy7, CD62L-BV421, CD11b-PE, CD11c-APC, and CD54-BV650 and cell suspension analysed on a Fortessa X20 cytometer. Marker surface expression was recorded on CD16+ neutrophils as median fluorescence intensity (MFI). Results: Both age and gender were similar between asthma (median age 65, with 55% males) and COPD (median age 72, with 50% males), while the healthy were predominantly females (75%) and were younger (median age 59) compared with COPD, p=0.003. The cell surface expression of CD62L was significantly reduced in COPD with a MFI (q1, q3) of 1138 (902, 1353) compared with asthma (1865 [1157, 2408]) and healthy controls (1946 [1041, 2688]), p=0.022. No significant differences were found for the other adhesion molecules tested. Conclusion: Blood neutrophils in COPD display reduced CD62L expression in comparison with asthma and healthy. The reduction in CD62L is suggestive of activation-associated shedding of CD62L, a process that takes place during the movement of neutrophils to the site of inflammation.