Influence of the electric charge of the antigen and the immune complex (IC) lattice on the IC activation of human complement

Abstract

Summary. In order to understand the mechanism of complement (C) activation by immune complexes (ICs), the anti-complementary effect of ICs containing cationized antigens was compared in vitro to that using ICs formed by native antigens. ICs were prepared with affinity-purified rabbit polyclonal IgG antibovine serum albumin (BSA) antibody and either native BSA (isoelectric point 4.2) or BSA rendered cationic by treatment with ethylenediamine (isoelectric point 9.4). Native and cationized antigens were characterized by isoelectric focusing. ICs containing anti-BSA IgG or F(ab H ) 2 , formed either at equivalence or in excess of native or cationized antigen, were submitted to ultracentrifugation in a sucrose gradient for mesh size determination. The anti-complementary effect of ICs was evaluated by kinetic determination of haemolytic activity of human serum on haemolysinsensitized sheep red blood cells. In conditions of antigen excess, the ICs formed by cationized BSA were significantly more efficient in activating human complement than those formed by native antigen. This higher activity was dependent on cationized antigen complexed with complete antibody molecules, as non-complexed cationized BSA or ICs prepared with F(ab H ) 2 fragments were inactive under the same experimental conditions. Furthermore, this difference did not depend on the mesh size of the immune Correspondence: Luciana Simon Pereira Crott, Departamento de Ana  lises Clõ Ânicas, Toxicolo  gicas e Bromatolo  gicas,

Novel grafted agar disks for the covalent immobilization of β‐D‐galactosidase

“…During the course of this experiment, the agar disks were soaked for 1 h in a 1% (w/v) solution (pH 8.5) of each of these four amine compounds. The pH 8.5 was selected as it is somewhat lower than the isoelectric point of EDA (PI 9.4) . Moreover, it was reported that about 18% of PEI would be protonated at pH 8.5 .…”

Formation, Clearance, Deposition, Pathogenicity, and Identification of Biopharmaceutical-related Immune Complexes

“…Antigen and antibody charge also affect IC lattice formation, complement activation, and tissue deposition (Gauthier and Mannik 1990; Michelin et al 2002; Theofilopoulos and Dixon 1979; Wener 2007). Cationic antigens bind to anionic sites in glomerular basement membrane, knee joint, or dermoepidermal junction as shown by injection of antigen or preformed ICs into mice, rats, or rabbits (Adler et al 1983; Border et al 1981; Gallo, Caulin-Glaser, and Lamm 1981; Gauthier and Mannik 1990; Isaacs and Miller 1982; Joselow, Gown, and Mannik 1985; Theofilopoulos and Dixon 1979; van den Berg and van de Putte 1985; Wener 2007).…”

Mechanisms of Immune Complex–Mediated Neutrophil Recruitment and Tissue Injury

“…subclass, size, charge, precipitability complement fixing abilities), can modulate the extent and location of IC deposition96. For example IC formed with an alteration in the ratio of antigen and antibody, or composed of cation antigen have a higher potential to activate and bind complement C1q 97, 98 an early component of the classical complement pathway, that promotes IC binding to endothelial cells 99, 100 and extracellular matrix molecules 88, 101, 102 and modifies the lattice structure of ICs to facilitate deposition 103. C1q also activates C3 to C3b.…”