Serum-treated antigen-antibody complexes inhibit the production of C2 and factor B by mononuclear phagocytes.
Antigen-antibody complexes enhanced the synthesis of C2 and factor B by human monocytes and macrophages, and C2 by guinea-pig macrophages. In contrast complexes that had been treated with serum inhibited the production of these components. The inhibitory effect of serum-treated complexes was abrogated by Fab fragments of anti-C3, anti-C3c and anti-C3d. It is therefore probable that inhibition was mediated by a C3 fragment bound to the complex. The enhancing effect of untreated complexes was reversible by serum-treated complexes, and the inhibitory action of serum-treated complexes was counteracted by untreated complexes. Such a system may be important in the regulation of the synthesis of complement components in response to local requirements.
D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology*; D001769:Blood; D001798:Blood Proteins / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D003175:Complement C2 / Q000096:biosynthesis*; D003176:Complement C3 / Q000276:immunology; D011415:Complement Factor B / Q000096:biosynthesis*; D004792:Enzyme Precursors / Q000096:biosynthesis*; D006168:Guinea Pigs; D006801:Humans; D008264:Macrophages / Q000276:immunology; D009000:Monocytes / Q000276:immunology; D010586:Phagocytes / Q000276:immunology*; D013997:Time Factors
D000936:Antigen-Antibody Complex; D001798:Blood Proteins; D003175:Complement C2; D003176:Complement C3; D004792:Enzyme Precursors; D011415:Complement Factor B