Oxidative response of human neutrophils, monocytes, and alveolar macrophages induced by unopsonized surface-adherent Staphylococcus aureus

In contrast to results with bacterial suspensions, phagocytosis of unopsonized bacteria readily occurs when bacteria are adhered to glass or plastic surfaces. However, in contrast to neutrophils, alveolar macrophages produced much less DNA denaturation as measured by acridine orange metachromasia of phagocytized Staphylococcus aureus. We have studied the phagocytosis of unopsonized surface-adherent S. aureus and the subsequent production of reactive oxygen species by peripheral blood neutrophils, monocytes, and alveolar macrophages. Phagocyte-free systems were then used to show the relationship of the reactive oxygen species produced by neutrophils and alveolar macrophages and the denaturation of unopsonized S. aureus DNA with acridine orange. Peripheral blood neutrophils, monocytes, and alveolar macrophages from normal human volunteers were added to vials with adherent S. aureus without opsonin. Bacterial uptake and luminol- and lucigenin-dependent chemiluminescence were measured. Neutrophils developed much greater luminol-dependent chemiluminescence than monocytes or alveolar macrophages. Compared with neutrophils and monocytes, alveolar macrophages developed significantly greater concentrations of superoxide, as measured by lucigenin-dependent chemiluminescence and ferricytochrome c reduction. These findings suggested that products of the myeloperoxidase-hydrogen peroxide-halide pathway were generated when peripheral blood neutrophils were stimulated and that alveolar macrophages primarily produced superoxide. When these reactive oxygen species were generated in phagocyte-free systems containing S. aureus, products of the myeloperoxidase-hydrogen peroxide-halide pathway produced denaturation of S. aureus DNA, whereas superoxide did not. Thus, differences in reactive oxygen species produced during phagocytosis may be related to the different capacities of neutrophils and alveolar macrophages to denature unopsonized adherent S. aureus DNA.</jats:p

Antimicrobial activities of dialysate-elicited and resident human peritoneal macrophages

Recent studies of the antimicrobial capacity of peritoneal macrophages (PM phi) isolated from patients undergoing chronic peritoneal dialysis have raised the question of whether these cells might be analogous to stimulated or activated murine PM phi. To explore this possibility, we compared PM phi from these patients (dialysate-elicited PM phi) with PM phi obtained from women undergoing laparoscopy (resident PM phi) in several in vitro assays of phagocyte function. Although bacterial phagocytosis by cells from both groups of donors was similar, significant differences were found in their chemiluminescence responses to opsonized zymosan. Although the mean peak luminol-enhanced chemiluminescence response of dialysate-elicited PM phi was 4.7 X 10(5) cpm, that of resident PM phi was only 1.3 X 10(5) cpm (P less than 0.05). In a lucigenin-enhanced chemiluminescence assay, dialysate-elicited PM phi again generated significantly greater chemiluminescence than did resident PM phi, suggesting that dialysate-elicited PM phi have a relatively increased capacity for O2- production. Using a fluorochrome microassay to assess the intracellular candidicidal activities of these cells, we found that dialysate-elicited PM phi killed 17% of cell-associated blastospores compared with only 1.5% killing by resident PM phi (P less than 0.05). These investigations led us to conclude that results of studies of the functional activity of dialysate-elicited PM phi cannot necessarily be extrapolated to resident PM phi and that dialysate-elicited PM phi do in some respects behave as stimulated or activated cells.</jats:p