Use of fluorescence polarization to monitor MHC-peptide interactions in solution

Area of Science:

• Biochemistry
• Immunology
• Biophysical Chemistry

Background:

• Class I Major Histocompatibility Complex (MHC) molecules present peptides to T cells, playing a critical role in immune responses.
• Understanding MHC-peptide interactions is vital for developing immunomodulatory therapies.

Purpose of the Study:

• To establish robust fluorescence polarization (FP) assays for investigating class I MHC-peptide interactions in solution.
• To quantify kinetic and equilibrium binding parameters for MHC/peptide complexes.
• To develop a high-throughput screening method for identifying compounds that modulate MHC-peptide binding.

Main Methods:

• Utilized fluorescein-labeled peptides to measure association and dissociation rate constants and equilibrium binding constants (KD).
• Developed a competition assay to determine half-maximal inhibitory concentrations (IC50) of unlabeled compounds.
• Employed microtiter-plate based FP measurements for rapid, solution-based analysis without separation steps.

Main Results:

• Demonstrated high reproducibility and sensitivity, requiring only picomolar amounts of labeled tracers.
• Achieved a high signal-to-noise ratio, enabling detection of low-affinity class I MHC ligands.
• Reduced analysis time to 10 seconds per sample using microtiter plates.

Conclusions:

• FP assays provide versatile and efficient tools for characterizing individual MHC-peptide interactions.
• These methods facilitate rapid screening of large compound libraries for potential immunomodulators.
• The assays are suitable for both detailed kinetic/equilibrium analysis and high-throughput screening applications.