Structural characterization of a cross-reactive idiotype shared by monoclonal antibodies specific for the human CD4 molecule.
A panel of mouse monoclonal anti-CD4 antibodies was characterized in terms of idiotypic expression by using specific anti-idiotypic antibody (anti-Id) reagents generated in rabbits immunized with anti-Leu3a, a monoclonal anti-CD4 which inhibits the human immunodeficiency virus (HIV) gp120 binding to CD4. Direct binding and competitive inhibition assays demonstrate that the majority of monoclonal anti-CD4 antibodies able to recognize CD4 epitopes overlapping the epitope recognized by anti-Leu3a expressed an antigen-combining site-related cross-reactive idiotype (IdX). Western blot analysis was used to demonstrate that this IdX is associated primarily with the light (L) chain of the monoclonal anti-CD4 antibodies. To further characterize the structural basis of the IdX, the nucleotide sequence of the variable region of the L kappa chain of anti-Leu3a was determined. Peptides corresponding to the first, second, and third complementarity determining regions (CDRs) of the L chain of anti-Leu3a were synthesized and used to immunize rabbits. All anti-peptide antisera recognized the immunizing peptide, the cognate anti-Leu3a molecule, and several other monoclonal anti-CD4 antibodies by direct binding assays. Western blot analysis utilizing the anti-CDR peptide reagents demonstrates that the reactivity to the monoclonal anti-CD4 antibodies was L chain-specific. The anti-Id generated by immunizing with the intact anti-Leu3a molecule failed to recognize the three L chain-derived CDR synthetic peptides, suggesting that the IdX requires the presence of the three-dimensional configuration of the L chain for its expression. The broad range of reactivity exhibited by the antipeptide antisera indicates that the majority of mouse monoclonal anti-CD4 antibodies characterized in this study utilize L chains encoded by a single germ line variable (V) region kappa (V kappa) chain gene or by V kappa genes that belong to the same gene family.
Attanasio
R
R
Department of Virology and Immunology, Southwest Foundation for Biomedical Research, San Antonio, Texas 78228-0147.
Dilley
D
D
Buck
D
D
Maino
V C
VC
Lohman
K L
KL
Kanda
P
P
Kennedy
R C
RC
D000595:Amino Acid Sequence; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001483:Base Sequence; D015153:Blotting, Western; D015704:CD4 Antigens / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology*; D007135:Immunoglobulin Variable Region; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D013379:Substrate Specificity
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D000939:Epitopes; D007130:Immunoglobulin Idiotypes; D007135:Immunoglobulin Variable Region