Peptides recognized by class I restricted T cells also bind to MHC class II molecules

Area of Science:

• Immunology
• Molecular Biology
• T cell biology

Background:

• T cell recognition mechanisms for MHC class I and II are similar.
• However, T cell determinants are often restricted to a single MHC class or few alleles.
• Potential structural differences between MHC class I and II restricted determinants are not fully understood.

Purpose of the Study:

• To investigate if MHC class I-restricted T cell determinants can bind to MHC class II molecules.
• To explore potential structural similarities or overlaps in antigen recognition between MHC class I and II pathways.
• To determine if peptides recognized by CD8+ T cells can interact with HLA-DR molecules.

Main Methods:

• Testing peptides previously identified as MHC class I restricted.
• Assessing peptide binding to HLA-DR molecules on B lymphoblastoid cell lines (B-LCL).
• Utilizing class II-negative B-LCL and transfected cell lines to confirm HLA-DR specificity.

Main Results:

• Four out of five tested MHC class I-restricted T cell determinants demonstrated binding to HLA-DR molecules on B-LCL.
• This binding was specifically inhibited by anti-HLA-DR monoclonal antibodies (mAb).
• Peptides did not bind to class II-negative cells but did bind to cells transfected with HLA-DR1.

Conclusions:

• MHC class I-restricted T cell determinants can bind to MHC class II molecules (HLA-DR).
• This suggests a potential overlap in the structural basis for T cell recognition across different MHC classes.
• Findings challenge the notion of strict MHC restriction and imply broader T cell epitope recognition.