γδ T cells recognize the insulin B:9-23 peptide antigen when it is dimerized through thiol oxidation

Area of Science:

• Immunology
• Molecular Biology
• Diabetes Research

Background:

• The insulin peptide B:9-23 is a key antigen in the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D).
• Both alpha beta (αβ) T cells and gamma delta (γδ) T cells, along with B cells, recognize this peptide and infiltrate pancreatic islets.
• Specific amino acid residues, Cys19 and Tyr16, play differential roles in T cell recognition of the peptide.

Purpose of the Study:

• To elucidate the distinct recognition mechanisms of γδ and αβ T cells towards the insulin B:9-23 peptide.
• To investigate the structural requirements for antigen recognition by different T cell subsets in type 1 diabetes.

Main Methods:

• Analysis of T cell responses to modified insulin B:9-23 peptides with specific amino acid substitutions (Cys19, Tyr16).
• Characterization of peptide structure in different redox states (reduced vs. oxidized).
• Assessment of T cell recognition based on peptide structure and MHC class II (I-A(g7)) complex formation.

Main Results:

• γδ T cells recognize an oxidized, disulfide-bonded homo-dimer of the insulin B:9-23 peptide, dependent on Cys19.
• αβ T cells recognize the reduced monomeric peptide, complexed with MHC class II molecule I-A(g7), requiring Tyr16.
• The dimerized peptide adopts a specific secondary structure, influenced by Tyr16, which is crucial for γδ T cell recognition, unlike the unstructured monomer.

Conclusions:

• γδ T cell recognition of the insulin B:9-23 peptide is dependent on its oxidized, dimerized form and specific secondary structure.
• Distinct structural conformations of the insulin peptide dictate recognition by different T cell receptor types (γδ vs. αβ), impacting type 1 diabetes pathogenesis.