The T Cell Receptor

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The T Cell Receptor

• September 24, 2002

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Receptor-Ligand Interactions
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Outline

• The T Cell Receptor Structure
• The T Cell Receptor Genetics
• The TCR/CD3 Complex
• CD4 and CD8 Coreceptors
• T Cell Alloreactivity

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Self-MHC Restriction Two Models

• T cells bind both self-MHC and antigen. How does
  this happen?
• Dual Receptor Model Each T cell has two
  receptors one binds antigen and one binds MHC
• Altered Self Model A single receptor on T cells
  binds both antigen and MHC

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Outline

• The T Cell Receptor Structure
• The T Cell Receptor Genetics
• The TCR/CD3 Complex
• CD4 and CD8 Coreceptors
• T Cell Alloreactivity

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Outline

• The T Cell Receptor Structure
• The T Cell Receptor Genetics
• The TCR/CD3 Complex
• CD4 and CD8 Coreceptors
• T Cell Alloreactivity

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Outline

• The T Cell Receptor Structure
• The T Cell Receptor Genetics
• The TCR/CD3 Complex
• CD4 and CD8 Coreceptors
• T Cell Alloreactivity

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CD4 and CD8 Coreceptors

• Divide most T cells into two subclasses based on
  function
• CD4 (Th) T cells recognize Ag/MHC Class II,
  while CD8 (Tc) T cells recognize Ag/MHC Class I
• Two features classify them as coreceptors
  recognition of peptide/MHC complex and signal
  transduction
• Members of Ig superfamily

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CD4 Coreceptors

• 55 kDa monomeric membrane glycoprotein
• Contains 4 Ig-like domains
• Long cytoplasmic tail contains 3 serine residues
  which can be phosphorylated
• Binds to b2 domain of MHC Class II molecules

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CD8 Coreceptors

• Glycoprotein consisting of two disulfide linked
  chains, each with a single Ig-like domain
• Can either be aa homodimer or ab heterodimer
• a and b chains are each 30-38 kDa
• Cytoplasmic tails contain several
  phosphorylatable a.a.s
• Binds to a2 and a3 domains of MHC Class I
  molecules

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Outline

• The T Cell Receptor Structure
• The T Cell Receptor Genetics
• The TCR/CD3 Complex
• CD4 and CD8 Coreceptors
• T Cell Alloreactivity

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