Segmental flexibility and complement fixation of genetically engineered chimeric human, rabbit and mouse antibodies

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Immunoglobulin G (IgG) is a crucial antibody isotype with diverse functions.
• Understanding the structure-function relationship of IgG is essential for immunology and therapeutic development.
• Previous studies have investigated IgG isotypes, but direct comparison of constant region effects is challenging.

Purpose of the Study:

• To generate and characterize chimeric IgG molecules with identical antigen-binding sites but varying heavy chain constant (CH) regions.
• To investigate the influence of CH regions on IgG segmental flexibility and complement fixation activity.
• To establish a structural basis for key IgG functions independent of variable region diversity.

Main Methods:

• Generation of chimeric IgG molecules combining specific antigen-combining sites with different CH regions.
• Measurement of segmental flexibility in engineered and naturally occurring IgG isotypes.
• Assay of complement fixation activity across the generated antibody family.
• Correlation analysis between measured properties and the length of the immunoglobulin hinge region.

Main Results:

• Chimeric IgG molecules with identical antigen-binding sites were successfully generated.
• Segmental flexibility and complement fixation activity varied among the different CH regions.
• Both flexibility and complement fixation correlated with the length of the immunoglobulin hinge region.
• The study identified a structural basis for CH-dependent IgG properties.

Conclusions:

• The heavy chain constant (CH) regions significantly influence IgG segmental flexibility and complement fixation.
• Hinge region length is a critical structural determinant for these CH-dependent antibody functions.
• This research provides insights into the structure-function relationships of immunoglobulin G molecules.