Inhibitory effect of lipopolysaccharide-stimulated P388D1 macrophage-like cells on plasmacytoma cells.

Culture supernatants of lipopolysaccharide-stimulated P388D1 macrophage-like tumor cells showed a growth inhibitory effect on plasmacytoma MOPC-315, MPC-11 and myeloma FO cells, but had no effect on J558 plasmacytoma cells. Based on the results of trypan blue staining and a 51Cr release assay, the supernatant had both cytotoxic and cytostatic activity for MOPC-315 plasmacytoma cells. The inhibitory activity was trypsin-sensitive, heat-stable at 100 degrees C for 20 min., but sensitive to 2-mercaptoethanol and cystein HCl. At least 6 hrs of exposure period were required for the P388D1 culture supernatant to show an inhibitory effect on plasmacytoma cells. Since the inhibitory activity could not be blocked by protease inhibitor or neutralized by antibodies to mouse IL-1 beta, IL-6 and TNF-alpha, the inhibitory factor(s) was distinct from the defined cytotoxic factors. After partial purification with DEAE-Sephacel and Sephacryl S-300 chromatography, four major active peaks with the molecular mass of 874-KDa (near the void volume), 112-KDa, 45-KDa and 18-KDa were obtained.