CD3 receptor

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In immunology, the CD3 antigen (CD stands for cluster of differentiation) is a protein complex composed of three distinct chains (CD3γ, CD3δ and CD3ε) in mammals, that associate with molecules known as the T cell receptor (TCR) and the ζ-chain to generate an activation signal in T lymphocytes. The TCR, ζ-chain and CD3 molecules together comprise the TCR complex. The CD3γ, CD3δ and CD3ε chains are highly related cell surface proteins of the immunoglobulin superfamily containing a single extracellular immunoglobulin domain. The transmembrane region of the CD3 chains is negatively charged, a characteristic that allows these chains to associate with the positively charged TCR chains (TCRα and TCRβ). The intracellular tails of the CD3 molecules contain a single conserved motif known as an immunoreceptor tyrosine-based activation motif or ITAM for short, which is essential for the signaling capacity of the TCR. Phosphorylation of the ITAM on CD3 renders the CD3 chain capable of binding an enzyme called Fyn, a kinase that is important in the signaling cascade of the T cell.

[edit] References

• Cellular and Molecular Immunology (5th Ed.) Abbas AK, and Lichtman, Editor: Saunders, Philadelphia, 2003.

The T cell receptor complex - edit
The antigen receptor: TCR| TCRα | TCRβ | TCRγ | TCRδ Accessory molecules: CD3 | CD3γ | CD3δ | CD3ε | ζ-chain (also called CD3ζ and TCRζ) Co-receptors: CD8 (with two glycoprotein chains CD8α and CD8β) | CD4 Ligands: MHC (MHC class I and MHC class II)