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Structural differences among monoclonal antibodies with distinct fine specificities and kinetic properties
T B Lavoie1, S Mohan, C A Lipschultz
1Department of Zoology, University of Maryland, College Park, MD USA.
Molecular Immunology
|March 4, 2000
Summary
Antibodies recognizing hen egg-white lysozyme (HEL) and DNP utilize similar germline genes, but somatic mutations create distinct antigen specificities and binding kinetics. These differences influence antibody robustness against antigen mutations, suggesting independent modulation during development.
Area of Science:
- Immunology
- Structural Biology
- Protein Engineering
Background:
- Monoclonal antibodies (mAbs) HyHEL-8, HyHEL-26, and HH10 recognize epitopes on hen egg-white lysozyme (HEL).
- The antibody XRPC-25 binds DNP but not HEL, despite structural similarities and shared germline gene usage with anti-HEL antibodies.
- Antibody-antigen interactions are governed by variable region gene usage and somatic mutations, influencing binding affinity and specificity.
Purpose of the Study:
- To investigate the role of germline gene usage and somatic mutations in antibody recognition of hen egg-white lysozyme (HEL) and DNP.
- To analyze how sequence differences in antibodies affect binding kinetics and sensitivity to antigen mutations.
- To understand the independent modulation of association and dissociation rates in antibody repertoire development.
Main Methods:
- Sequencing of variable regions of anti-HEL and anti-DNP monoclonal antibodies.
- Analysis of germline gene usage (Vk23, VH36-60) for selected antibodies.
- Measurement of antibody-antigen binding kinetics (association and dissociation rates) using natural variants and site-directed mutants of lysozyme.
- Comparison of antibody affinities and their sensitivity to antigenic mutations.
Main Results:
- Monoclonal antibodies HyHEL-8, HyHEL-26, and HH10 (anti-HEL) and XRPC-25 (anti-DNP) share Vk23 and VH36-60 germline genes, demonstrating recognition of distinct antigens via similar genetic origins.
- Somatic sequence differences in antibody variable regions lead to varied binding kinetics and differential sensitivity to mutations in HEL.
- Antibody HyHEL-8 exhibits mutation-insensitive binding rates, HH10 shows mutation-sensitive association, and HH26 displays variable rates, all modulated by minimal amino acid differences.
Conclusions:
- The same germline genes can generate antibodies recognizing unrelated antigens (HEL and DNP) through somatic diversification.
- Antibody binding kinetics, specifically association and dissociation rates, can be independently modulated to control sensitivity to antigen mutations.
- These findings provide insights into the mechanisms governing antibody repertoire development and fine-tuning of immune responses.