Different cell surface and phagocytic properties in mononuclear phagocytes from blood and alveoli

Abstract

Flow cytofluorometry was used to compare blood monocytes (BMs) and alveolar macrophages (AMs) from the same nonsmoking subject (n = 13). Autofluorescence was quantified, cell surface markers (HLA-DR, CR3) were detected by monoclonal antibodies, and phagocytic ability was determined using C3b-coated yeast particles. AMs expressed more HLA-DR (p < 0.001) and CR3 (p < 0.01) on their surfaces than did AMs. The phagocytic capacity was enhanced in EMs compared to BMs (p < 0.001) and the cells showed an increased autofluorescence (p < 0.001) in the alveoli compared to blood. The findings suggest that the mononuclear phagocyte is activated when it migrates from blood to alveoli in order to adapt to the milieu in the alveolar space.