Systemic neutrophil activation in acute preschool viral wheeze

Background: In preschool children, attacks of wheeze are usually triggered by viral colds. The inflammatory substrate in preschool viral wheeze (PVW) is unclear, but epidemiological data suggest that most PVW is not caused by allergic inflammation. We therefore speculated that the neutrophils are an important effector cell. Systemic neutrophil activation is the first stage for the development of pulmonary neutrophilia. Markers of neutrophil activation are shedding of the adhesion molecule L-selectin from the cell surface upregulation of Mac-1 expression, and an increase in serum soluble L-selectin. Aims: To obtain evidence for systemic neutrophil activation during PVW. Methods: Preschool children (1-5 years) admitted to hospital with acute PVW (n = 20) and normal controls (n = 18) were studied. Adhesion molecule expression on CD16 positive neutrophils was determined in both groups and expressed as molecules of equivalent fluorochrome (MEF). Serum soluble L-selectin was analysed by ELISA. Results: Compared with controls, children with PVW had reduced neutrophil L-selectin expression (median MEF (IQR): 69 (11 to 96) units versus 136 (109 to 163) units, p < 0.001) and higher serum soluble L-selectin (2.8 (2.3 to 3.1) versus 2.4 (2.2 to 2.6) mu g/ml, p = 0.04). There was no significant difference in neutrophil Mac-1 expression. Conclusion: Systemic neutrophil activation is associated with acute PVW.