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Structural model for T-cell recognition of HLA class II-associated alloepitopes
1Department of Laboratory Medicine/Pathology and Surgery, University of Minnesota, Minneapolis 55455.
Human Immunology
|January 1, 1990
Summary
Investigating human leukocyte antigen (HLA) class II molecules reveals key amino acid regions crucial for T-cell recognition and alloepitope expression, linking specific sequences to shared epitopes. This research clarifies HLA structure-function relationships.
Area of Science:
- Immunogenetics
- Molecular immunology
- T-cell immunology
Background:
- Human Leukocyte Antigen (HLA) class II molecules play a critical role in immune responses by presenting peptides to T-cells.
- Understanding the structure-function relationship of HLA molecules is essential for comprehending T-cell recognition and alloepitope expression.
- Polymorphic epitopes on HLA molecules are recognized by T-cells, influencing immune system function and transplantation outcomes.
Purpose of the Study:
- To investigate the structure-function relationship of HLA class II molecules concerning alloepitope expression.
- To define polymorphic epitopes on HLA-DR and HLA-DQ molecules using cloned T-cell reagents.
- To identify associations between shared DNA sequences and shared T-cell-defined epitopes on HLA molecules.
Main Methods:
- Generation of T-cell clones from cells primed against HLA-DR2 haplotypes.
- Monoclonal antibody inhibition assays to determine DR- or DQ-directed T-cell responses.
- Panel cell analysis using DR2-positive and DR2-negative target cells.
- Comparison of DNA sequences of HLA-DR and HLA-DQ alleles expressing similar epitopes.
Main Results:
- Specific amino acid residues (DR: 67, 70, 71, 74; DQ: 57, 70, 71) on the alpha helix are critical for T-cell recognition.
- Sharing of the second (aa 25-33) and third (aa 67-74) hypervariable regions is necessary for some DR epitope sharing.
- The findings suggest the second hypervariable region influences peptide binding, while the third region impacts T-cell receptor interaction.
Conclusions:
- Specific amino acid sequences within HLA class II molecules directly correlate with the expression of alloepitopes.
- Alloepitope expression involves a complex interplay between HLA molecule structure, bound peptide, and T-cell receptor recognition.
- Some shared alloepitopes could not be explained by primary sequence homology, suggesting potential conformational or peptide-dependent mechanisms.