T-cell receptor on CD4-positive and CD8-positive T cells (TCR)

The T-cell receptor (TCR), present on CD4-positive (helper) and CD8-positive (cytotoxic) T cells, is a multiprotein complex responsible for recognizing antigenic peptides presented by major histocompatibility complex (MHC) molecules on antigen-presenting cells[2][6][7]. The canonical TCR consists of highly variable alpha and beta chains, which confer specificity for antigen, and are noncovalently associated with invariant CD3 signaling subunits (CD3γ, δ, ε, ζ)[2][5]. TCR signaling requires co-receptors CD4 or CD8 depending on the cell type: CD4 interacts with MHC class II, while CD8 associates with MHC class I—the co-receptor engagement recruits the tyrosine kinase Lck and greatly augments TCR signaling[1][3][7]. Upon activation, the TCR/CD3 complex triggers a highly regulated cascade involving phosphorylation of ITAMs, recruitment of Zap-70, SLP-76, LAT, and ultimately results in T-cell activation, proliferation, differentiation, and effector function[2][4][5][8]. Aberrant or excessive TCR activation can cause autoimmunity or systemic toxicity, and agents that modulate TCR signaling are used clinically in cancer immunotherapy or to induce immune tolerance.

Other names

TCRAlpha-beta T-cell receptorT-cell antigen receptorTCR/CD3 complex

Monoclonal antibody binding blocks or modulates TCR signaling (e.g., anti-CD3 antibodies block TCR-mediated activation). Bispecific antibodies (e.g., blinatumomab) redirect TCR engagement to tumor antigens. Immunosuppressive agents dampen TCR-induced proliferation is induced by interfering signaling or co-stimulation.