title: A newly discovered function for C1 inhibitor, removal of the entire C1qr2s2 complex from immobilized human IgG subclasses.
abstract: A new function for C1 inhibitor (C1 INH) is reported. C1 inhibitor dislodged the entire activated C1 complex (C1qr2s2) from immobilized human IgG. C1 binding to doses of immobilized human IgG3, IgG1, or IgG2 was quantified as a function of time. When human serum, as a source of C1qr2s2, was added to relatively low doses of immobilized IgG, C1q binding peaked at 1.0 min then gradually decreased. However when purified C1q was applied to immobilized IgG, C1q binding did not diminish with time. The removal of C1q was duplicated by adding purified C1 INH to C1qr2s2 which had been bound to immobilized IgG. The dislodgement of C1q from immobilized IgG required the presence of intact C1qr2s2 and of C1 INH. This removal of C1q by purified C1 INH was prevented when activated C1s was used to neutralize C1 INH function or when relatively high levels of IgG were immobilized.
authors.affiliation: Department of Microbiology and Immunology, College of Dental Medicine, Medical University of South Carolina, Charleston 29425-2230, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Chen
authors.forename: R J
authors.initials: RJ
authors.lastname: Boackle
mesh_terms: D001667:Binding, Competitive; D003174:Complement C1 Inactivator Proteins / Q000502:physiology*; D015922:Complement C1q / Q000378:metabolism*; D015923:Complement C1r / Q000378:metabolism*; D003181:Complement C4 / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D046911:Macromolecular Substances; D011485:Protein Binding
chemical_list: D003174:Complement C1 Inactivator Proteins; D003181:Complement C4; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D015922:Complement C1q; D015923:Complement C1r