title: In vitro synthesis of factor B of the alternative pathway of complement activation by mouse peritoneal macrophages.
abstract: Factor B of the alternative pathway of complement activation was shown to be synthesized and secreted by unstimulated mouse peritoneal macrophages. The activity of B in the culture supernatants from macrophage monolayers was detected by consumption of C3 in reaction mixtures containing supernatant and guinea pig factors C3, D and insoluble C3b. Using a monospecific antiserum, factor B in concentrated culture supernatants was shown by immunodiffusion and immunoelectrophoresis to be identical to factor B in mouse plasma and to form a characteristic complex with cobra venom factor in the presence of D. A steady rate of factor B secretion was observed for 4 days providing the medium was changed every 24 h. Cycloheximide (0.5 mug/ml), an inhibitor of protein synthesis, caused inhibition (90%) of factor B production. Incubation of culture medium containing 14C-labeled amino acids with the macrophage monolayer resulted in incorporation of radioactivity into factor B as detected by autoradiography of precipitation lines formed with anti-B antiserum; This indicated that synthesis of factor B had occurred. In the same culture supernatants the presence of newly synthesized C3 was also demonstrated.
mesh_terms: D000818:Animals; D001202:Ascitic Fluid / Q000166:cytology; D002478:Cells, Cultured; D003176:Complement C3 / Q000096:biosynthesis* / Q000378:metabolism; D003165:Complement System Proteins / Q000096:biosynthesis*; D003513:Cycloheximide / Q000494:pharmacology; D006023:Glycoproteins / Q000096:biosynthesis*; D006168:Guinea Pigs; D007700:Kinetics; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011414:Properdin / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D003176:Complement C3; D006023:Glycoproteins; D011414:Properdin; D003165:Complement System Proteins; D003513:Cycloheximide