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Synonyms: 4930549J05RIK, AW552088, CD16Z, CD247, CD3, CD3 NU, CD3-ZETA, CD3H, CD3Q, CD3Z, T3Z, TCR ZETA, TCRk, TCRZ

T-Cell Receptor and CD3 Complex

The T cell receptor-TCR.CD3 (TCR.CD3) complex is a multimeric structure on T-cells that recognizes, binds to, and is activated by antigen presenting cell (APC)-associated antigen bound major histocompatibility complex (pMHC). This association is facilitated by colocalization of TCR.CD3 and CD8 receptors in lipid raft regions and the interaction of CD8 with the constant region of the MHC tetramer and the CD3 component of the TCR.CD3 receptor.

The TCR receptor complex is composed of six subunits. Two of these complexes become cross-linked and activated upon antigen (pMHC) binding. Two subunits each, TCRalphabeta or TCRgammadelta, make up the variable region or the TCR receptor complex associated with the cell surface that interacts with the antigen and MHC. Consequently, there are Ti-TCRalphabeta type and Ti-TCRgammadelta type T-cell receptors. T-cell receptor complexes also contain four CD3 subunits. They can contain two zeta subunits, one epsilon subunit and either a gamma or delta subunit. CD3gamma and CD3delta subunits have similar sequences. Antigen binding leads to the cross-linking and activation of the TCR hexamers. The binding of pMHC by the TCR-CD3 complex is preceded by an association between the CD8alphabeta heterodimer with the MHC constant region and the CD3 complex.

T-cell receptor signaling leads to T-cell activation and IL-2 production in a complex process that centers on the immunological synapse (IS). Activating receptor clusters and their underlying “signalosomes” form within the IS. The immunological synapse is a bilayer structure that forms at the interface of antigen presenting cells (APC) and antigen-primed T-cells. In the mature synapse, the co-receptors, TCR/CD3-CD8 and CD28, aggregate in the central supramolecular activation complex (c-SMAC) and structural molecules, such as the integrin LFA1 and the scaffold protein talin accumulate in the peripheral supramolecular activation complex (p-SMAC).