INHIBITORY EFFECT OF LIPOPOLYSACCHARIDE-STIMULATED P388D1 MACROPHAGE-LIKE CELLS ON PLASMACYTOMA CELLS

Culture supernatants of lipopolysaccharide-stimulated P388D1 macrophag e-like tumor cells showed a growth inhibitory effect on plasmacytoma M OPC-315, MPC-11 and myeloma F0 cells, but had no effect on J558 plasma cytoma cells. Based on the results of trypan blue staining and a Cr-51 release assay, the supernatant had both cytotoxic and cytostatic acti vity for MOPC-315 plasmacytoma cells. The inhibitory activity was tryp sin-sensitive, heat-stable at 100-degrees-C for 20 min., but sensitive to 2-mercaptoethanol and cystein . HCl. At least 6 hrs of exposure pe riod were required for the P388D1 culture supernatant to show an inhib itory effect on plasmacytoma cells. Since the inhibitory activity coul d not be blocked by protease inhibitor or neutralized by antibodies to mouse IL-1beta, IL-6 and TNF-alpha, the inhibitory factor(s) was dist inct from the defined cytotoxic factors. After partial purification wi th 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.