CD3 antigen (T cell co-receptor) (CD3)

The **CD3 antigen** is a multimeric protein complex and a definitive surface marker of **T cells**, where it functions as a key component of the T cell receptor (TCR) complex[1][3][7]. It consists of four main subunits: CD3γ, CD3δ, CD3ε, and CD3ζ, assembled as three dimers (γε, δε, ζζ), each with transmembrane and cytoplasmic domains containing immunoreceptor tyrosine-based activation motifs (ITAMs)[1][3][5][7]. CD3 associates non-covalently with the TCR and mediates signal transduction upon antigen recognition, leading to T cell activation, proliferation, differentiation, and effector function[1][2][3][7]. Because of its central role in T cell biology, **CD3 is a major therapeutic target** in immunology—for example, by using anti-CD3 antibodies to either activate or suppress the immune response in settings including transplantation, autoimmunity, and cancer immunotherapy[2][6][7]. CD3 is broadly expressed on all mature T cells, making it a standard marker for T cell identification and quantification in research and clinical diagnostics[5][7]. Notable clinical risks of therapeutics targeting CD3 include cytokine release syndrome and increased susceptibility to infection due to immunosuppression[2][7].

Other names

Cluster of Differentiation 3T3 antigenCD3 complexT cell co-receptor

TCR signaling modulation, Immune modulation via T cell activation or depletion, Induction of T cell apoptosis (in some therapeutic contexts), Immune synapse formation