A sensitive method to detect defined peptide among those eluted from murine MHC class II molecules

Area of Science:

• Immunology
• Biochemistry
• Analytical Chemistry

Background:

• Major histocompatibility complex (MHC) class II molecules present peptides to CD4+ T cells.
• Identifying specific peptides bound to MHC class II is crucial for understanding immune responses.
• Current methods for peptide identification can be complex and require significant sample amounts.

Purpose of the Study:

• To develop a sensitive radioimmunoassay for detecting and quantifying peptides eluted from MHC class II molecules.
• To validate the assay's ability to identify specific antigenic peptides.
• To provide a tool for discovering microbial peptides presented by MHC class II.

Main Methods:

• Development of a competitive inhibition radioimmunoassay using a synthetic hemagglutinin (HA) peptide and specific antibodies.
• Fractionation of eluted peptides from pulsed cells (2PK3 B lymphoma cells) using reversed-phase high-performance liquid chromatography (RP-HPLC).
• Testing RP-HPLC fractions for inhibitory activity in the radioimmunoassay, correlating with peptide presence via sequencing.

Main Results:

• The radioimmunoassay detected picomole quantities of a defined peptide (HA110-120) eluted from MHC class II molecules.
• Significant inhibitory activity was observed, corresponding to the presence of the HA110-120 peptide.
• The assay demonstrated reproducibility and sensitivity down to 1 pmol of antigenic peptide.

Conclusions:

• A sensitive and reproducible radioimmunoassay was established for tracing specific peptides bound to MHC class II molecules.
• This assay facilitates the identification of microbial peptides with defined structures and antigenicity.
• The method offers a valuable tool for immunologists and researchers studying antigen presentation.