Tuning DO:DM Ratios Modulates MHC Class II Immunopeptidomes

Area of Science:

• Immunology
• Molecular Biology
• Proteomics

Background:

• Major histocompatibility complex class II (MHC-II) antigen presentation is vital for immune responses.
• Regulation of MHC-II by HLA-DM (DM) and HLA-DO (DO) is not fully understood due to technical limitations.
• Existing computational tools lack the ability to account for DO and DM activities.

Purpose of the Study:

• To create model antigen-presenting cell (APC) systems expressing MHC-II peptidome regulators at variable levels.
• To investigate the impact of varying DO:DM ratios on peptide presentation.
• To develop computational tools that incorporate DO and DM activities for improved prediction.

Main Methods:

• Generated a panel of HLA-DR4-expressing APC lines with diverse DO:DM ratios.
• Employed a combined immunopeptidomic and proteomic discovery strategy.
• Analyzed over 10,000 unique DR4-presented peptides to assess presentation changes.

Main Results:

• Identified key peptide characteristics influencing presentation based on DO:DM ratios.
• These characteristics include DM sensitivity, peptide abundance, binding affinity, motif, length, and binding register.
• Demonstrated significant alterations in peptide presentation profiles across different DO:DM states.

Conclusions:

• The developed APC lines provide a valuable model for studying MHC-II peptidome regulation.
• Findings offer insights into peptide selection mechanisms influenced by DO and DM.
• Implications for enhancing HLA-II prediction algorithms and understanding APC functions in immunity.