title: The role of Fc:Fc interactions in insoluble immune complex formation and complement activation.
abstract: The initial rate of formation of insoluble immune complexes from rabbit IgG and ovalbumin was approximately 12 times that for formation of F(ab')2-ovalbumin complexes. At low IgG concns, in the range 0.7-2.7 nM, the formation of insoluble immune complexes was characterised by a lag phase, especially for complexes formed in low antigen excess, compared to antibody excess. Guanidine HCl (at concns up to 0.5 M) and urea (at concns up to 1 M) decreased the initial rates of formation of IgG immune complexes more than F(ab')2 immune complexes. Pre-formed IgG immune complexes were solubilised at lower guanidine HCl concns than were F(ab')2 immune complexes. C1q enhanced the initial rate of formation of IgG immune complexes at C1q:IgG ratios up to 1:1. Higher C1q concns decreased the initial rate of formation of the complexes. Urea (1 M) blocked the C1q mediated enhancement of immune complex formation.
authors.affiliation: Department of Biochemistry, University of Sydney, Australia.
authors.forename: S B
authors.initials: SB
authors.lastname: Easterbrook-Smith
authors.forename: R J
authors.initials: RJ
authors.lastname: Vandenberg
authors.forename: J R
authors.initials: JR
authors.lastname: Alden
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology*; D003167:Complement Activation; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D010047:Ovalbumin / Q000276:immunology; D011489:Protein Denaturation; D012995:Solubility
chemical_list: D000936:Antigen-Antibody Complex; D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D010047:Ovalbumin