Figure 13.

Cryo-EM structure of the TCR-CD3 holo-complex. CD3 contains 4 chains- δ, γ, ε and ζ that forms three dimers. Each of δ, γ and ε chains contains an ECD, a TM and an ICD contains an immunoreceptor-tyrosine-based activation motif (ITAM), whereas CD3ζ contains a short extracellular loop, a TM and an ICD with three ITAMs.

The TCRα/TCRβ/CD3 complex is assembled by the TCRαβ, CD3γε, CD3δε, and CD3ζζ dimers in a 1:1:1:1 stoichiometry. Activation of the complex by the antigenic peptide/MHC complex leads to phosphorylation of ITAMs of CD3.