CD3 T-cell coreceptor complex (CD3)

The CD3 T-cell coreceptor complex is a vital multi-subunit protein assembly essential for T-cell signaling and activation. It consists of four distinct chains—CD3γ, CD3δ, CD3ε, and CD3ζ—which non-covalently associate with the T-cell receptor (TCR) to form the TCR-CD3 complex (UniProt P07766). Upon antigen binding to the TCR, the CD3 subunits transmit activation signals into the T cell via immunoreceptor tyrosine-based activation motifs (ITAMs), triggering immune responses (PubMed: 29305535). In modern oncology, CD3 is a cornerstone target for bispecific T-cell engagers (BiTEs) and bispecific antibodies, which use an anti-CD3 single-chain variable fragment (scFv) to physically link T cells to tumor cells. This interaction induces MHC-independent T-cell activation and directed lysis of the cancer cell (PubMed: 32661153). While highly effective in treating B-cell malignancies and other cancers, targeting CD3 can lead to significant systemic inflammatory responses, most notably cytokine release syndrome (CRS) (PubMed: 30635916).

Other names

Cluster of Differentiation 3T3 complexT-cell receptor-associated CD3 complexCD3 epsilon/delta/gamma/zeta complex

Bispecific antibodies or BiTEs utilize an anti-CD3 scFv domain to bind the CD3 epsilon subunit on T cells while simultaneously binding a tumor-associated antigen on a target cell. This dual binding creates a cytolytic synapse, bypassing the requirement for traditional MHC-I antigen presentation and TCR specificity, leading to the release of perforins and granzymes that induce apoptosis in the target cell (PubMed: 29305535, FDA: Blincyto Label).