SERUM-MEDIATED MODIFICATION OF PROLIFERATION IN FACTOR-DEPENDENT MACROPHAGE CELL-LINES

Previously we described that bacterial lipopolysaccharide (LPS) promot ed DNA synthesis and supported the cell viability in the factor-depend ent macrophage cell lines BDM-1 and BDM-1W3 in the absence of colony-s timulating factor (CSF). To further examine this phenomenon, in the pr esent study we examined th effects of serum on CSF-dependent prolifera tion and LPS-induced DNA synthesis in BDM-1 and BDM-1W3 cells. Fetal c alf serum (FCS) was required for CSF-dependent proliferation in BDM-1 and BDM-1W3 cells. FCS was also required for LPS-induced DNA synthesis in BDM-1W3 cells. However, at concentrations higher than 0.2%, FCS in hibited LPS-induced DNA synthesis in BDM-1W3 cells in a dose-dependent manner. To obtain the inhibitory activity in FCS(FCS-In) for LPS-indu ced DNA synthesis, FCS was fractionated by gel filtration chromatograp hy using Sephacryl S-200, chromatography on DEAE-Sephacel, and affinit y chromatography on heparin-Sepharose. FCS-In was eluted in the void v olume peak from a Sephacryl S-200 column, indicating that FCS-In has a molecular weight of more that 250,000. The molecular weight of FCS-In was apparently 270,000 as determined by SDS-polyacrylamide gel electr ophoresis (PAGE) under non-reducing conditions. Upon reduction, four c omponents became detectable with apparent molecular weights of 170,000 , 110,000, 67,000, and 30,000. The inhibitory activity in FCS-In mater ial was inactivated by heat and trypsin treatment. The partially purif ied FCS-In inhibited LPS-induced DNA synthesis in BDM-1W3 cells, but d id not inhibit the proliferation of BDM-1W3 cells induced by IL-3, gra nulocyte-macrophage CSF (GM-CSF), or macrophage CSF (M-CSF). These res ults indicate that the inhibition by FCS-In is specific to LPS. Althou gh the site and mechanism of inhibition are not know, FCS-In may funct ion in vivo by modulating the interaction of LPS with macrophages.