Cell surface expression of class II MHC proteins bound by a single peptide

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Class II Major Histocompatibility Complex (MHC) proteins normally present diverse peptides.
• A method to present a single, defined peptide species on MHC class II would be valuable for research.

Purpose of the Study:

• To construct and express cells presenting a single, covalently linked peptide on MHC class II molecules.
• To investigate the stability and recognition of these engineered peptide-MHC complexes.

Main Methods:

• A gene encoding a covalent linkage between an MHC class II beta-chain (IA beta b) and a specific peptide (E alpha 52-68) was created.
• This gene, along with the corresponding alpha-chain gene (IA alpha b), was transfected into B lymphoma cells and fibroblasts.
• Expression and recognition of the resulting IAb-E alpha complex by monoclonal antibodies and T cells were analyzed.

Main Results:

• The engineered IAb-E alpha complex was expressed on cell surfaces and recognized by specific antibodies and T cells.
• On fibroblasts, the peptide remained largely attached to the MHC beta-chain, with nearly all MHC occupied by the E alpha peptide.
• On B lymphoma cells, some degradation of the covalent linker and/or peptide occurred.
• T cell hybridoma responses indicated that peptide recognition is crucial for MHC interactions.

Conclusions:

• Engineered cells can present a single, defined peptide covalently bound to MHC class II molecules.
• The stability of the covalent linkage varies between cell types.
• These findings support the concept that T cell recognition of MHC molecules is influenced by the bound peptides.