The role of the functional maturation of alveolar macrophages and alveolar lining materials in lung defenses
Sugimoto, M.; Ando, M.; Senba, H.; Horio, S.; Tokuomi, H.
Nihon Kyobu Shikkan Gakkai Zasshi 18(11): 780-786
1980
ISSN/ISBN: 0301-1542 PMID: 6270435 Document Number: 160485
Alveolar macrophages and lung lavage fluids were obtained from adult and neonatal rabbit lungs by tracheobronchial lavage. The alveolar macrophages were assayed for nitroblue tetrazolium (NBT) reduction and superoxide production with or without lung lavage fluids which contained alveolar lining materials. When alveolar macrophages were exposed to lung lavage fluids from adult rabbits, enhanced NBT reduction and superoxide production were observed. The amount of NBT reduction and superoxide produced by neonatal alveolar macrophages was < 1/4 of that produced by adult alveolar macrophages. The difference of superoxide production between adult and neonatal alveolar macrophages could not be explained only by the difference of IgG receptors on the surface of cells. No difference was found in the NAD(P)H oxidase activity of the postnuclear fractions obtained from adult and neonatal alveolar macrophages. The postnuclear fractions from the alveolar macrophages which were stimulated with the adult lung lavage fluids showed the same activity of NAD(P)H oxidase as those of control alveolar macrophages. Neonatal alveolar macrophages showed decreased activity of lysosomal and mitochondrial enzymes as compared to adult alveolar macrophages. The functional immaturity of neonatal alveolar macrophages was suggested. The lung lavage fluids from neonatal rabbits which contained less IgG and more phospholipids had no effect on the superoxide production by both adult and neonatal alveolar macrophages. Thus, neonates showed immaturity of both alveolar macrophages and alveolar lining materials. These results may explain the frequent and serious infections of the lung in human neonates.