Structural analysis of IgG2A monoclonal antibodies in relation to complement deposition and renal immune complex deposition.
This study explores the structural features of murine monoclonal IgG2a anti-dinitrophenyl (DNP) antibodies that were previously shown to form immune complexes (IC) differing in their capacity to bind complement, their clearance from the circulation and their deposition in the kidney. Interestingly, the sequence of one of these antibodies has a missing stretch of 14 amino acids within FR3. Molecular modeling suggests that this sequence deletion corresponds to the loss of beta-pleated sheet structure for two beta-strands (designated 4-3 and 4-4) on the external surface of the V(H) domain. Despite this sequence and conformational abnormality, the antibody retains affinity for DNP comparable to other IgG2a antibodies. Data presented here identify monoclonal IgG2a antibodies that form IC with varying propensity for both complement binding and renal deposition and yet have similar V(H) domain sequences. In fact, in the case of two IgG2a antibodies that form IC with very different renal tropisms and complement binding capacity, sequence variation within V(H) was observed only at three clustered residues within FR2, a single residue within FR3 and nine clustered residues spanning CDR3 and FR4. Sequence and modeling analysis also yielded the paradoxical finding that an antibody forming IC with a relatively high capacity to serve as a target for complement binding displays a relatively low number of solvent exposed acceptor residues for C4b and C3b. These data underscore the complex relationship between V domain structure, complement activation and renal deposition of model IC.
Gonzalez
Melva L
ML
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Biomedical Sciences Building, Room 1053, P.O. Box 26901, Oklahoma City, OK 73190, USA.
Frank
Mark Barton
MB
Ramsland
Paul A
PA
Hanas
Jay S
JS
Waxman
Frank J
FJ
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D000915:Antibody Affinity; D000936:Antigen-Antibody Complex / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D003165:Complement System Proteins / Q000276:immunology* / Q000378:metabolism; D007074:Immunoglobulin G / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D007668:Kidney / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D003165:Complement System Proteins