The effect of reactive oxygen metabolites (ROM) on the attachment and ingestion phases of C3b- and IgG-mediated phagocytosis by macrophages.

The effects of enzymatically produced reactive oxygen metabolites (ROM) on the attachment and ingestion phases of C3b- and IgG-mediated phagocytosis by cultured mouse peritoneal macrophages (MPM) was investigated using a hypoxanthine-xanthine oxidase ROM-generating system. ROM-exposure at a dose which did not affect cell viability caused a slight decrease in the percentage of phagocytosing cells. The total number of cell-associated (attached and ingested) C3b- and IgG-coated particles initially decreased in relation to controls. After 120 min the number of attached and ingested C3b-particles had returned to the level of controls, while the corresponding value for IgG-particles lagged behind. The number of ingested particles decreased in both C3b- and IgG-groups at each time-point studied (30-150 min). A linear increase in the formation of lipid peroxidation products was measured during the period of observation, while transmission electron microscopical studies showed largely intact morphology. These results indicate that ROM species may induce membrane-related changes in inflammatory cells such as macrophages, probably due to lipid peroxidation; affecting the binding functions of the C3b- and Fc-receptors, without any obvious alteration in cellular fine structure.