title: Inefficient binding of IgM immune complexes to erythrocyte C3b-C4b receptors (CR1) and weak incorporation of C3b-iC3b into the complexes.
abstract: The binding of soluble complement-reacted IgM immune complexes (IC) to erythrocyte (E) C3b-C4b receptors (CR1) and the incorporation of C3b-iC3b into solid phase IgM-IC was investigated. The optimal binding of liquid phase IgM-IC to E-CR1 was obtained with IC formed at moderate antibody excess, but the binding was low (2-3%) when compared to the binding of the corresponding IgG-IC (50-60%). Solid phase IC were prepared by coating microwells with heat-aggregated bovine serum albumin (BSA) followed by incubation with rabbit IgM anti-BSA antibody. The IC were reacted with human serum at 37 degrees C. The binding of C3b-iC3b was determined by use of biotinylated F(ab')2 antibodies to C3b-C3c and avidin-coupled alkaline phosphatase. The incorporation of C3b-iC3b into solid-phase IgM-IC increased when increasing amounts of IgM antibody were reacted with the antigen. The binding reaction was slow, reaching a maximum after about 2 h at 37 degrees C. The binding of C3b-iC3b to the IgM-IC was remarkably inefficient when compared to the incorporation into IgG-IC reacted with the same amounts of BSA-precipitating antibody.
authors.affiliation: Third Department of Medicine, University Medical School, Debrecen, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Kávai
authors.forename: J M
authors.initials: JM
authors.lastname: Rasmussen
authors.forename: G
authors.initials: G
authors.lastname: Baatrup
authors.forename: A
authors.initials: A
authors.lastname: Zsindely
authors.forename: S E
authors.initials: SE
authors.lastname: Svehag
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000378:metabolism*; D001666:Binding Sites, Antibody; D002417:Cattle; D003179:Complement C3b / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D007075:Immunoglobulin M / Q000378:metabolism*; D011817:Rabbits; D011951:Receptors, Complement / Q000378:metabolism*; D017463:Receptors, Complement 3b; D012710:Serum Albumin, Bovine / Q000276:immunology
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D012710:Serum Albumin, Bovine; D003179:Complement C3b