title: Distinction between fixation of C1 and the activation of complement by natural IgM anti-hapten antibody: effect of cell surface hapten density.
mesh_terms: D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology*; D003168:Complement Fixation Tests; D004306:Dose-Response Relationship, Immunologic; D006241:Haptens / Q000276:immunology*; D006461:Hemolysis; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology*; D002955:Leucovorin / Q000276:immunology; D008727:Methotrexate / Q000276:immunology
chemical_list: D003172:Complement C1; D006241:Haptens; D007075:Immunoglobulin M; D002955:Leucovorin; D008727:Methotrexate