Small macrophages are present in early childhood respiratory disease

BackgroundRecently, an established “small macrophage” phenotype has been observed in the sputum of patients with CF and COPD. However, little is known about the prevalence of this phenotype in the airways of young children. Since respiratory inflammation begins early in CF, we hypothesised that these small macrophages would be increased in paediatric CF bronchoalveolar lavage (BAL).MethodsMacrophage populations in CF and disease control BAL were assessed by multicolour flow cytometry. BAL inflammatory indices were collected as part of the AREST-CF programme.ResultsSmall macrophages were present in CF (n = 35, mean 36 ± 12% of BAL macrophages) but not significantly different to the respiratory disease controls (n = 7, mean 40 ± 21%). Number of small macrophages correlated significantly with number of BAL neutrophils (r = 0.44, p < 0.01) but not infection or IL-8.ConclusionsIn paediatric patients small macrophages are not unique to CF, but their establishment as the dominant phenotype in adults may be due to chronicity of inflammation and infection.