Inhibition of the classical activation pathway of complement-mediated lysis by monoclonal antibodies to complement components C3c and C3d

• Published in: Transfusion (Philadelphia, Pa.) Vol. 32; no. 5; p. 430
• Main Authors: Mushens, R E, Bakacs, T
• Format: Journal Article
• Language: English
• Published: United States 01.06.1992
• Subjects: Antibodies, Monoclonal - immunology; Antibody Specificity; Complement C3c - immunology; Complement C3d - immunology; Complement Pathway, Classical - immunology; Cytotoxicity, Immunologic; Epitopes; Humans
• ISSN: 0041-1132
• DOI: 10.1046/j.1537-2995.1992.32592327716.x

Eight epitope-mapped monoclonal antibodies (MoAbs) to complement component C3d and five to complement component C3c were investigated to determine whether they could inhibit the classical activation pathway of complement-mediated lysis (CML) by using blood group AB red cells sensitized by A or B MoAbs. Three IgM C3d MoAbs and one IgG1 C3c MoAb were able to inhibit CML in a dose-dependent manner. In the presence of excess complement, no inhibition was observed. The greatest inhibition was observed with two high-affinity IgM antibodies that were specific for epitope 1 on the C3d component. Some inhibition was observed with a high-affinity IgM antibody specific for epitope 3 of the C3d component and also with a lower-affinity IgG antibody specific for epitope 1 of the C3c component. The results indicate that some complement MoAbs have the capacity to distinguish between conformationally and/or functionally different forms of red cell-bound C3.