Surface properties of antigen-antibody complexes

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Antibody surface properties are crucial for immune responses.
• Understanding antigen-antibody interactions requires characterizing complex surface dynamics.
• Existing methods may not fully capture the overall surface changes upon antigen binding.

Purpose of the Study:

• To compare the surface properties of intact antibodies before and after antigen binding.
• To investigate how different antibody isotypes (IgG, IgA1, IgA2, IgE, IgM) and antigen types affect complex surface characteristics.
• To determine if antigen binding induces conformational changes in antibodies.

Main Methods:

• Utilizing liquid-liquid partition chromatography in an aqueous two-phase system.
• Analyzing the overall surface properties of antibodies in solution.
• Comparing surface properties of free antibodies versus antigen-antibody complexes.

Main Results:

• Antigen-antibody complex surface properties depend on antibody variable regions, antigen type, and conformational changes.
• IgG antibodies' antigen-binding sites remained exposed after hapten or hapten-carrier binding.
• Other antibody isotypes (IgA1, IgA2, IgE, IgM) showed concealed binding sites and conformational changes upon protein binding, with surfaces resembling the antigen.
• IgA, IgE, and IgM antibodies underwent conformational changes, altering their heavy chain constant regions' surface properties, unlike IgG antibodies.

Conclusions:

• Liquid-liquid partition chromatography is a valuable tool for studying antibody surface properties and antigen interactions.
• Antibody isotype dictates the surface characteristics of antigen-antibody complexes and the occurrence of conformational changes.
• Antigen binding can significantly remodel antibody surfaces, with implications for immune recognition and effector functions.