title: Monoclonal anti-mouse macrophage antibodies recognize the globular portions of C1q, a subcomponent of the first component of complement.
abstract: One of seven monoclonal antibodies generated against mouse macrophages (M phi) was found to recognize isolated heterologous C1q. This antibody was shown to be cytotoxic and to react in a strain-independent way with mouse M phi derived from bone marrow cells as well as with M phi from the peritoneal cavity; it did not react, however, with mouse granulocytes, thymocytes, or T and B lymphocytes. The hemolytic activity of fluid phase C1q was inhibited to 50% at a 2 X 10(-4) dilution of hybridoma supernatant, whereas a 100-fold higher concentration was required to inhibit C1q bound to immune complexes ( EAC1q ) to the same extent. It was demonstrated that this antibody recognizes the isolated globular, Fc-binding portions of the C1q molecule and reacts with the A and B chains. Because M phi have been shown to synthesize C1q, the Fc-recognizing subcomponent of the first component of complement, evidence was provided that endogeneous C1q can serve as an Fc receptor on M phi during secretion. This fact was demonstrated by a dose-dependent inhibition of Fc-receptor activity for EIgG by the F(ab')2 fragment of this monoclonal antibody. These experiments further support the concept that C1q produced by M phi functions on the surface as an Fc-recognizing molecule before it is released and incorporated into the macromolecular complex of serum C1.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000502:physiology; D000918:Antibody Specificity; D000936:Antigen-Antibody Complex / Q000378:metabolism; D000937:Antigen-Antibody Reactions; D001667:Binding, Competitive; D003166:Complement Activating Enzymes / Q000032:analysis / Q000276:immunology*; D003167:Complement Activation; D003172:Complement C1 / Q000378:metabolism; D015922:Complement C1q; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008809:Mice, Inbred C3H; D051381:Rats; D011920:Rats, Inbred WF; D011961:Receptors, Fc / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D003172:Complement C1; D011961:Receptors, Fc; D015922:Complement C1q; D003166:Complement Activating Enzymes