Quantitatively Resolving Ligand-Receptor Bonds on Cell Surfaces Using Force-Induced Remnant Magnetization...

Area of Science:

• Biophysics
• Cell Biology
• Immunology

Background:

• Molecule-specific noncovalent bonding is crucial for cell surface recognition and function.
• Distinguishing specific molecular bonds from nonspecific interactions in complex cellular environments remains a challenge.
• Understanding these interactions is key to advancing cellular recognition studies.

Purpose of the Study:

• To quantitatively resolve specific molecular bonds from nonspecific interactions on cell surfaces.
• To measure and compare the binding forces of antibody-antigen interactions in different environments.
• To investigate the impact of the cellular environment on protein-protein interactions.

Main Methods:

• Utilized force-induced remnant magnetization spectroscopy (FIRMS) for high-resolution force measurements.
• Applied FIRMS to magnetic beads with anti-CD4 antibodies interacting with CD4(+) T cells.
• Compared binding forces on cell surfaces versus functionalized substrate surfaces.

Main Results:

• FIRMS quantitatively resolved three distinct interactions on CD4(+) T cell surfaces.
• The binding force of CD4 antibody-antigen bonds was 75 ± 3 pN on T cells and 90 ± 6 pN on a substrate.
• A 15 pN difference in binding force was observed, attributed to conformational or environmental variations of CD4 antigens.

Conclusions:

• FIRMS offers high force resolution and detection efficiency for studying cell surface interactions.
• The cellular environment significantly impacts molecular binding forces, as demonstrated by the CD4 antibody-antigen interaction.
• This technique is valuable for elucidating protein-protein interactions in complex biological systems.