Related Experiment Videos
Effect of pH on MHC class II-peptide interactions
A Sette1, S Southwood, D O'Sullivan
1Cytel, San Diego, CA 92121.
Journal of Immunology (Baltimore, Md. : 1950)
|February 1, 1992
Summary
Acidic pH enhances many MHC class II-peptide interactions, but effects vary by MHC molecule and peptide. This pH-dependent binding impacts immune responses by altering peptide binding affinity and available binding sites.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- MHC class II molecules present peptides to T helper cells, a critical step in adaptive immunity.
- The binding affinity of peptides to MHC class II molecules is influenced by various factors, including pH.
- Understanding pH-dependent binding is crucial for deciphering immune responses and developing peptide-based therapies.
Purpose of the Study:
- To investigate the impact of pH on the binding of peptides to diverse mouse and human MHC class II molecules.
- To elucidate the mechanisms underlying pH-dependent MHC class II-peptide interactions.
- To determine if pH influences the kinetics and equilibrium of MHC class II-peptide complex formation.
Main Methods:
- Direct binding assays were performed using various mouse (IAd, IAk, IEd, IEk) and human (DR1, DR5, DR7) MHC specificities with eight different class II-restricted determinants.
- Kinetic and equilibrium analyses were conducted on three specific class II-peptide combinations (IAd/OVA 323-339, IAk/HEL 46-61, and DR1/HA 307-319).
- Analysis included measuring peptide binding capacity across a range of pH values (4.5 to 7.0).
Main Results:
- Acidic conditions generally increased the binding capacity of many class II-peptide combinations.
- Optimal binding pH varied, with IE molecules favoring pH 4.5 and IA molecules favoring pH 5.5-6.5; DR molecules showed minimal pH effects.
- Acidic pH affected both the association (on) and dissociation (off) rates of class II-peptide complexes, leading to varied equilibrium affinities.
- For IAd/OVA 323-339, acidic pH increased available binding sites by promoting dissociation of endogenous peptides.
Conclusions:
- The effect of pH on MHC class II-peptide binding is complex and molecule/peptide-specific, defying simple rules.
- Acidic pH can modulate immune responses by altering the stability and repertoire of presented peptides.
- Understanding these pH-dependent dynamics is vital for vaccine design and immunotherapy strategies.