Different cell surface and phagocytic properties in mononuclear phagocytes from blood and alveoli. A comparative study of blood monocytes and alveolar macrophages from human nonsmokers using flow cytofluorometry.

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 less than 0.001) and CR3 (p less than 0.01) on their surfaces than did BMs. The phagocytic capacity was enhanced in AMs compared to BMs (p less than 0.001) and the cells showed an increased autofluorescence (p less than 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.