INDUCTION OF MACROPHAGE BINDING TO VIRALLY INFECTED-CELLS BY LOW-LEVELS OF LIPOPOLYSACCHARIDE

Bone marrow culture-derived macrophages (BMCM) and vesicular stomatitis virus-infected BALB/c-3T3 cells (3T3-VSV) were used to determine whether macrophages could be activated to bind virally infected cells. Although lipopolysaccharide (LPS)activated BMCM bound some uninfected BALB/c-3T3 cells, the number of targets that were bound increased with increasing times between infection and assay. Furthermore, LPS-activated BMCM bound more 3T3-VSV cells than did control macrophages. As more targets were added, the number of targets bound by the unactivated macrophages remained relatively level. However, the number of targets bound by the activated macrophages increased with increasing concentrations of added targets until they reached a plateau that was eight times greater than that bound by the unactivated BMCM. When BMCM were exposed to LPS for 24 h before assay, they lost both their ability to bind to 3T3-VSV and their cytolytic activity against those targets, However, as when using P815, a standard tumor target, the acquisition of binding of 3T3-VSV could be separated from macrophage cytolytic activity against those targets. The amount of LPS required to activated BMCM for increased binding of 3T3-VSV cells was 10-100 times lower than that needed to induce cytolytic activity for 3T3-VSV cells, Each of these values was approximately 100-fold lower than the amount of LPS required to induce the corresponding activity (binding or cytotoxicity) by using P815 targets.