CD3 antigen (cluster of differentiation 3) (CD3)

The CD3 antigen is a multimeric cell-surface complex found exclusively on T cells, composed of four invariant polypeptide chains—gamma (γ), delta (δ), epsilon (ε), and zeta (ζ)—that associate as three dimers (γε, δε, ζζ)[7][2]. CD3 is non-covalently bound to the T-cell receptor (TCR) and is critical for intracellular signaling upon antigen recognition. Its cytoplasmic tails contain immunoreceptor tyrosine-based activation motifs (ITAMs) that serve as docking and activation sites for kinases following TCR engagement, allowing T cell activation, proliferation, and cytokine release[2][1][7]. CD3 is a therapeutic target in immunology, with monoclonal antibodies and bispecific agents (such as blinatumomab) leveraging CD3 to redirect or suppress T cell activity in cancer, autoimmune diseases, and transplantation medicine[7][5]. CD3 expression is also used as a pan-T cell marker in laboratory diagnostics[7].\nThe original query refers to cytotoxicity mediated by CD3-positive cells—these are typically CD8+ cytotoxic T lymphocytes, but the molecular target is **CD3**, not the functional phenotype.

Other names

cluster of differentiation 3CD3 complexT-cell co-receptor

Antibody or biologic binding to CD3 triggers T cell activation and cytotoxicity, sometimes redirecting T cells against tumor or target cells\nCan induce depletion or modulation of T cells (immunosuppression)