T lymphocyte antigen CD3, commonly referred to as CD3 or the CD3 complex (CD3)

The CD3 complex is a multimeric cell surface protein complex present on all mature T lymphocytes and is crucial for T cell development and signaling. CD3 comprises four different chains: gamma (γ), delta (δ), epsilon (ε), and zeta (ζ), which pair to form three dimers (εγ, εδ, ζζ). These chains noncovalently associate with the T cell receptor (TCR) and function collectively as the TCR-CD3 complex, which mediates both antigen recognition (by TCR) and transduces activation signals upon antigen binding (by CD3 via immunoreceptor tyrosine-based activation motifs, ITAMs). The CD3 complex is indispensable for the adaptive immune response and is a defining feature of the T cell lineage. Therapeutically, CD3 is targeted for immunosuppression, as well as in emerging immuno-oncology therapies, and serves as a diagnostic marker in hematological malignancies and immune profiling.

Other names

Cluster of differentiation 3T3 complex (historical name)CD3 complexCD3 glycoprotein complex

Antibody-induced modulation/depletion of T cells (antibodies targeting CD3 induce T cell apoptosis or anergy) Immunosuppressive action via inhibition of T cell activation/signaling Induction of cytokine release syndrome in the context of potent activation or depletion Modulation of immune synapse and signalosome formation, downstream signaling