PHOSPHATIDYLINOSITOLMANNOSIDE-BASED LIPOSOMES INDUCE NO SYNTHASE IN PRIMED MOUSE PERITONEAL-MACROPHAGES

Liposomes prepared from phosphatidylinositolmannosides (extracted from BCG) and cholesterol are efficiently endocytosed by macrophages. Phag ocytosis of particles or microbes modifies macrophage metabolism and i n some cases, delivers potent stimulating signals to macrophages. We e xamined the effect of phosphatidylinositolmannoside-based liposomes on three macrophage functions especially important for host defenses : n itric oxide production, oxidative burst and TNF-alpha secretion. Phosp hatidylinositolmannoside-based liposomes, added as empty vesicles, ind uced a strong NO synthase activity in mouse peritoneal macrophages pri med either by interferon-gamma or by trehalose dimycolate. They also i nduced a moderate production of TNF-alpha. Phosphatidylinositolmannosi des conferred activating properties to pH-sensitive liposomes. In cont rast, liposomes composed of phosphatidylcholine and phosphatidylserine were unable to activate primed macrophages. (C) 1995 Academic Press, Inc.