[Effect of surfactant on mouse alveolar macrophage cytotoxicity]

Surfactant has been shown to have several immunologic activities in addition to its property of lowering tension. To investigate the effect of surfactant on alveolar macrophage cytotoxicity against tumor cells, we compared the cytolytic activity, tumor necrosis factor (TNF) activity and L-arginine-dependent NO2- production of mouse alveolar macrophages in the presence of surfactant with those of alveolar macrophages alone. Furthermore, we measured the concentrations of inositol-1,4,5, triphosphate (IP3) and diacylglycerol (DG) both of which are second messengers of intracellular signals. Cytolysis, TNF activity and NO2- production were enhanced by lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). This enhancement was further increased by addition of surfactant. The surfactant did not enhance the concentration of IP3, but enhanced that of DG in alveolar macrophages activated by LPS or IFN-gamma. These data suggest that surfactant upregulated the enhancement of alveolar macrophage cytotoxicity by LPS and IFN-gamma, and this effect was related to an increase in the concentration of DG in activated alveolar macrophages.