title: Monoclonal rheumatoid factor-IgG immune complexes. Poor fixation of opsonic C4 and C3 despite efficient complement activation.
abstract: Monoclonal IgM rheumatoid factor forms complexes with IgG in essential mixed cryoglobulinemia. We demonstrate that such complexes fix C3 and C4 poorly, although efficient fluid-phase C3 conversion can occur. Fixation of small amounts of C4 may be sufficient to generate a C3 convertase, but may prevent subsequent fixation of C3 by competing for binding sites on the complex. These complexes bind inefficiently to normal erythrocyte complement receptor type 1 (CR1) in vitro, and are undetectable on erythrocytes of patients with essential mixed cryoglobulinemia in vivo. Clearance of such phlogistic complexes from tissues by CR1-bearing cells may be inefficient.
authors.affiliation: Rheumatology Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
authors.forename: Y C
authors.initials: YC
authors.lastname: Ng
authors.forename: D K
authors.initials: DK
authors.lastname: Peters
authors.forename: M J
authors.initials: MJ
authors.lastname: Walport
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000936:Antigen-Antibody Complex / Q000276:immunology*; D003167:Complement Activation; D003176:Complement C3 / Q000276:immunology*; D003181:Complement C4 / Q000276:immunology*; D003168:Complement Fixation Tests; D003449:Cryoglobulinemia / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D012217:Rheumatoid Factor / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D003176:Complement C3; D003181:Complement C4; D007074:Immunoglobulin G; D012217:Rheumatoid Factor