T cell activity correlates with oligomeric peptide-major histocompatibility complex binding on T cell surface.

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• CD8+ T cells distinguish self from non-self peptide-major histocompatibility complexes (pMHC) to identify virally infected cells.
• Recognition of foreign pMHC triggers transplant rejection (allotransplant and xenotransplant).

Purpose of the Study:

• To investigate the peptide-dependent recognition of xenogeneic (human HLA-A2.1) and syngeneic (murine H-2 D(b)) class I MHC molecules by the murine T cell clone AHIII12.2.
• To understand how alterations in antigenic peptides affect T cell responsiveness and binding kinetics.

Main Methods:

• Utilized crystal structures of peptide-bound HLA-A2.1 (agonist, null, antagonist peptides).
• Employed class I pMHC octamers to assess T cell activity and binding affinity.
• Measured pMHC multimer binding half-lives on the T cell surface.

Main Results:

• Peptide sequence significantly alters AHIII12.2 T cell responsiveness to HLA-A2.1.
• Crystal structures provide insights into peptide-MHC interactions influencing T cell recognition.
• A strong correlation exists between T cell activity and pMHC complex affinity for the T cell receptor.
• Observed similar half-lives for pMHC multimers bound to AHIII12.2, contrasting with previous studies.

Conclusions:

• T cell receptor affinity is a critical determinant of T cell responses to diverse peptide-MHC complexes.
• Understanding these interactions is crucial for managing transplant rejection and developing T cell-based immunotherapies.
• The observed binding kinetics suggest a complex interplay between affinity and T cell activation thresholds.