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Studies on antigen binding by intact and hinge-deleted chimeric antibodies
C Horgan1, K Brown, S H Pincus
1Laboratory of Microbial Structure and Function, Rocky Mountain Laboratories, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840.
Journal of Immunology (Baltimore, Md. : 1950)
|June 15, 1993
Summary
The IgG4 antibody hinge may limit antigen binding affinity. Removing the hinge in IgG4 improved binding, suggesting structural constraints unique to this antibody type.
Area of Science:
- Immunology
- Protein Engineering
Background:
- Antibody structure, specifically the hinge region, influences antigen binding.
- Immunoglobulin G (IgG) subclasses, like IgG1 and IgG4, have distinct properties.
- The role of the IgG hinge in antigen binding affinity remains incompletely understood.
Purpose of the Study:
- To investigate the impact of the IgG hinge on antigen binding.
- To compare the binding characteristics of IgG1 and IgG4 antibodies with and without hinges.
- To elucidate the structural constraints imposed by the IgG4 hinge.
Main Methods:
- Engineered matched sets of chimeric IgG1 and IgG4 antibodies with and without hinges.
- Utilized identical V regions and either IgG1 or IgG4 C regions.
- Measured antibody binding to a peptide antigen and peptide-BSA conjugates with varying epitope densities.
Main Results:
- Intact IgG1 bound free peptide better than hinge-deleted IgG1.
- Intact IgG4 exhibited lower binding affinity to antigens compared to IgG1.
- Hinge-deleted IgG4 showed improved binding affinity, comparable to IgG1, and did not activate complement.
- The IgG4 hinge appears to impose a structural constraint limiting high-affinity binding.
Conclusions:
- The IgG hinge plays a critical role in modulating antigen binding affinity.
- The IgG4 hinge may be responsible for its typically lower observed binding affinity.
- Hinge-deleted IgG4 antibodies demonstrate enhanced binding capabilities, offering insights into antibody engineering.