title: Synthesis of complement factor B by the human monocyte U-937 cell line. Augmentation by immunostimulatory agents.
abstract: The human pre-monocytic cell line U-937 was shown to synthesize and to secrete increasing amounts of factor B in short term cultures in serum-free medium containing BSA. The kinetics of factor B production were higher on day 2 than on days 1 and 3. The production of factor B was reversibly inhibited by cycloheximide, indicating de novo synthesis. Metabolic labeling with [35S]-methionine and SDS-PAGE analysis revealed that both intracellular and secreted factor B were single-chain proteins with similar m.w. (90,000), which co-migrated with purified plasma factor B. Incubation of U-937 cells with the immunostimulants PMA, LPS, IFN-gamma, and IL-1 resulted in a dose-dependent augmentation of factor B production. A 24-h exposure to IL-1 was shown to be required for maximal stimulation. A combination of suboptimal doses of LPS and IFN-gamma was shown to exert a synergistic effect on factor B production. The U-937 cell line is thus a valuable model for the study of the regulation of the factor B gene expression.
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D002460:Cell Line; D002474:Cell-Free System; D011415:Complement Factor B / Q000096:biosynthesis* / Q000302:isolation & purification; D004306:Dose-Response Relationship, Immunologic; D004792:Enzyme Precursors / Q000096:biosynthesis*; D006461:Hemolysis; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008715:Methionine; D009000:Monocytes / Q000276:immunology / Q000378:metabolism*; D011233:Precipitin Tests; D013462:Sulfur Radioisotopes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000276:Adjuvants, Immunologic; D004792:Enzyme Precursors; D007375:Interleukin-1; D008070:Lipopolysaccharides; D013462:Sulfur Radioisotopes; D007371:Interferon-gamma; D008715:Methionine; D011415:Complement Factor B; D013755:Tetradecanoylphorbol Acetate