Activation of hemolytic complement by mouse monoclonal IgG1 antibody: comparison with rabbit IgG.
We investigated the ability of a mouse anti-hapten monoclonal IgG1 antibody (Ab) to bind to cell-bound specific hapten and to fix and activate C1 and thus the lytic sequence of complement (C). In a comparative study with polyclonal rabbit anti-hapten IgG Ab, we found that about 6 times more monoclonal Ab molecules than polyclonal were necessary for the generation of 1 hemolytic site/cell: the data were interpreted to mean that a cluster of four cell-bound monoclonal Ab molecules was necessary to bind C1 and activate C-mediated hemolysis. Experiments performed under conditions of low density of cell-bound hapten and excess of antibody showed that both monoclonal and polyclonal IgG Abs were able to react only with 20-30% of the cell-bound hapten and that both Abs recognized the same hapten specificity. We also found that even though monoclonal IgG1 Ab was able to bind strongly to a protein A-Sepharose column and could be eluted only by a low-pH buffer, the purified Ab, when bound to cell surface hapten, showed a weak ability to react with free protein A.
Battista
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P
Circolo
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A
Borsos
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T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes / Q000276:immunology; D006241:Haptens / Q000276:immunology; D006461:Hemolysis; D007074:Immunoglobulin G / Q000276:immunology*; D008727:Methotrexate / Q000276:immunology; D051379:Mice; D011817:Rabbits; D013205:Staphylococcal Protein A / Q000276:immunology
D000911:Antibodies, Monoclonal; D003172:Complement C1; D000939:Epitopes; D006241:Haptens; D007074:Immunoglobulin G; D013205:Staphylococcal Protein A; D008727:Methotrexate