Definition of a human suppressor T-cell epitope

Area of Science:

• Immunology
• Molecular Biology
• Vaccinology

Background:

• Regulatory and helper T (Th) cell responses are crucial for vaccine development and immunomodulation.
• Antigen presentation by major histocompatibility complex (MHC) molecules influences T-cell subset activation.
• CD4+ suppressor T (Ts) cells in leprosy down-regulate Mycobacterium-specific Th cell responses, but their recognized antigens remain unidentified.

Purpose of the Study:

• To investigate the role of antigen and HLA in controlling T-cell subset activation.
• To identify the specific antigens recognized by CD4+ Ts cells in lepromatous leprosy.
• To explore the potential of specific peptide-HLA interactions in exclusively activating Ts cells.

Main Methods:

• Isolation and characterization of CD4+ Ts cell clones from lepromatous leprosy patients.
• Epitope mapping of antigens recognized by Ts cell clones using mycobacterial hsp65.
• Analysis of T-cell receptor (TCR) alpha and beta chain expression to assess clonal origin.

Main Results:

• All HLA-DR2-restricted CD4+ Ts cell clones recognized an epitope within residues 439-448 of mycobacterial hsp65.
• This epitope was presented by HLA-DRB1*1503, an HLA-DR2 variant.
• Non-suppressor T-cell clones recognized different antigens and were stimulated by other HLA-DR2 variants.
• Peptide 435-449 and recombinant hsp65 exclusively induced Ts cells in this patient.
• Ts clones recognizing the specific epitope originated from diverse progenitors, indicated by varied TCRs.

Conclusions:

• A specific peptide-HLA class II combination can exclusively activate Ts cells.
• This discovery offers insights into the mechanisms of T-cell regulation in leprosy.
• Findings may inform the development of targeted immunotherapies and vaccines.