Human alveolar macrophages and monocytes generate the functional classical pathway of complement in vitro.
Binding of labelled protein to EIgM kept with macrophage or monocyte cultures with 3H-leucine under serum-free conditions, shows that de novo synthesis of protein with affinity to EIgM takes place. We find that monoclonal anti-C3c and anti-C3g antibodies and polyclonal anti-C4 and anti-C5 antibodies bind to such erythrocytes. This demonstrates that C4b, C3b and iC3b are deposited on the EIgM. Additional evidence for complement synthesis is the increase in binding of anti-C4 antibodies to EIgM when the incubation time was increased from 48 to 96 hours. Stimulation of the mononuclear phagocyte cultures with ET was necessary to obtain significant amounts of erythrocyte-bound complement proteins. From these results we conclude that the functional classical pathway of complement is produced in vitro by the monocytes and macrophages.
D002478:Cells, Cultured; D003167:Complement Activation; D003171:Complement Pathway, Classical; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D066298:In Vitro Techniques; D008264:Macrophages / Q000502:physiology*; D008297:Male; D009000:Monocytes / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000276:immunology
D007075:Immunoglobulin M; D003165:Complement System Proteins