A B S T R A n . Using a Teflon culture system we analyzed different aspects of cell maturation and phagocytic activities in neonatal monocyte-derived macrophages. Morphological and cytochemical characteristics as well as the protein composition of neonatal macrophages were identical with those of adult controls; actin binding protein (265,000 Da), myosin (210,000), a-actinin (102,000) and actin (42,000) could be identified in cells from either source: ~l l phagocytic functions were shown to be perfectly normal in neonatal macrophages when compared with adult cells: random migration, chemotactic response to zymosanactivated serum and formyl-methionyl-leucyl-phenylalanin, ingestion, and killing of Staphylococcus aureus, phagocytosis-associated chemiluminescence, production of oxygen intermediates (superoxide anion, 0;; hydrogenperoxide, H202). Phorbol myristate acetate-stimulated 0;-generation by 1 x lo5 macrophages was 11.8 f 4.7 nmol/h for neonates, and 10.2 f 3.9 for controls; production of H 2 0 2 was 7.6 f 3.5 nmol/h in neonatal macrophages and 6.4 +. In newborns, who suffer an increased susceptibility to serious systemic infections, subnormal phagocyte functions have been described. Neutrophils from neonates showed a decreased deformability (1) and a marked deficiency in movement toward different chemotactic stimuli (2-6). In addition generation of .OH by neonatal neutrophils was shown to be decreased (7). However, neonatal monocytes exhibited basically normal phagocytic functions when compared with adult cells (8). The functions of neonatal macrophages have not been fully explored. Macrophages from newborns synthesize humoral host defense factors such as complement components C2, C4 to a similar extent as phagocytes from adults (9, 10); fibronectin production Received October 12, 1987; accepted April 7, 1988. Correspondence Christian P. Speer, M.D., Universitats-Kinderklinik, RobertKoch-Str. 40, D-3400 Gottingen, Federal Republic of Germany.Supported by Grant Sp 239/2-2 from the Deutsche Forschungsgemeinschaft.2 1 was shown to be decreased in neonatal macrophages (9). Macrophages from newborns who had been activated by interferon-7 effectively killed or inhibited replication of toxoplasma gondii (1 I), presentation of bacterial Ag, and production of interleukin 1 was normal in cord blood monocytes/macrophages (12, 13). However, it has been suggested, that the decreased production of interferon-y by human neonatal cells (13) could be due to a functionally immature macrophage (14). Our study was initiated to examine the principal phagocyte activities of monocyte-derived macrophages in response to inflammation, i.e. chemotaxis, phagocytosis, killing, and generation of oxygen metabolites. Momholonical studies included a detailed analysis of the protein compos~ion of macrophages. MATERIALS AND METHODS Cell separation. Umbilical venous blood was withdrawn fromthe placenta into heparin (1-20 U/ml) immediately after delivery of healthy term newborns who were products of an uncomplicated pregnancy, normal labor, and...

Monocytes play an essential role in cellular host defense as circulating phagocytes, as well as precursors of macrophages. We investigated the principal phagocytic activities in monocytes from cord blood of term infants by analysing adherence, random migration, chemotaxis, bactericidal activity, phagocytosis-associated chemiluminescence, production of superoxide anion (O-2) and generation of hydrogen peroxide (H2O2). All phagocytic functions of monocytes from neonates were shown quantitatively to be comparable to those of cells from healthy adult volunteers. The increased susceptibility of the human neonate to serious systemic infections cannot be related to an abnormality in monocyte function.