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Interaction between CD8 and major histocompatibility complex (MHC) class I mediated by multiple contact surfaces that

J Sun1, D J Leahy, P B Kavathas

  • 1Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8035, USA.

The Journal of Experimental Medicine
|November 1, 1995
PubMed

Insights

Researchers identified key residues in MHC class I that are critical for binding to CD8, a coreceptor on cytotoxic T lymphocytes. This finding supports a bivalent interaction model between CD8 and MHC class I molecules.

Area of Science:

  • Immunology
  • Molecular Biology
  • Structural Biology

Background:

  • CD8 is a crucial coreceptor for T cell receptor (TCR) function on cytotoxic T lymphocytes.
  • Understanding CD8-MHC class I interactions is vital for T cell immunity.
  • Previous studies predicted CD8 interacts with both alpha 2 and alpha 3 domains of MHC class I.

Purpose of the Study:

  • To identify specific residues in MHC class I essential for CD8 binding.
  • To elucidate the structural basis of the CD8-MHC class I interaction.
  • To validate a bivalent interaction model between CD8 and MHC class I.

Main Methods:

  • Mutational analysis of the MHC class I binding site for CD8.
  • Cell-cell adhesion assays to quantify binding interactions.
  • Structural analysis of residue positioning within MHC class I.

Main Results:

  • Three critical residues (Q115, D122, E128) in the alpha 2 domain of MHC class I were identified.
  • These residues' side chains are positioned in a cavity, suggesting direct contact with CD8.
  • Experimental data support a model where one CD8 alpha/alpha homodimer binds two MHC class I molecules.

Conclusions:

  • Specific residues in the MHC class I alpha 2 domain are essential for CD8 interaction.
  • The findings provide strong support for a bivalent binding model of CD8 and MHC class I.
  • This work deepens our understanding of T cell coreceptor function and immune synapse formation.

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