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===TCR Complex===

===TCR Complex===

[[Image:TCR Complex.jpg|thumb|right|250px|TCR Complex - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]

[[Image:TCR Complex.jpg|thumb|right|250px|TCR Complex - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]

The T cell Receptor, or TCR is always associated with CD3 which is referred to as the '''TCR complex'''. TCR is expressed on the surface of T cells in a noncovalent association with a complex of transmembrane polypeptides.  

The T cell Receptor, or TCR is always associated with CD3, forming what is referred to as the '''TCR complex'''. TCR is expressed on the surface of T cells in a noncovalent association with a complex of transmembrane polypeptides.  

CD3 contains 3 distinct polypeptide chains that are expressed exclusively on T cells: γ, ε, and δ. These molecules are members of the Ig superfamily - the ε chain associates with both γ and δ - and they play a 'chaperone' role in transporting newly synthesized TCR molecules to the cell surface.

CD3 contains 3 distinct polypeptide chains that are expressed exclusively on T cells: γ, ε, and δ. These molecules are members of the Ig superfamily - the ε chain associates with both γ and δ - and they play a 'chaperone' role in transporting newly synthesized TCR molecules to the cell surface.