T-cell receptor complex (TCR) (TCR)

Cytotoxic T cell activation is a fundamental process of adaptive immunity characterized by the engagement of the T-cell receptor complex (TCR) on CD8+ T lymphocytes with antigenic peptides presented by major histocompatibility complex class I (MHC I) molecules on target cells. The activation requires co-stimulatory signals, typically through CD28 interacting with CD80/CD86 on antigen-presenting cells, and leads to proliferation and differentiation of CD8+ T cells into effector cytotoxic T lymphocytes (CTLs). Once activated, CTLs execute cytotoxicity by directly killing infected, malignant, or dysfunctional cells via release of cytolytic granules (perforin, granzymes) or engagement of apoptotic pathways (Fas–FasL). CD4+ T cells can also acquire cytotoxic functions under specific conditions. This process is central to immune surveillance, cancer immunotherapy, and the response to infection, but is also implicated in autoimmunity and certain adverse effects of immunotherapy.

Other names

TCRCD8 co-receptorcytotoxic T cell/T lymphocytekiller T cellCTLCD8+ T cellcytolytic T cellT-killer cell

Activation or inhibition of T-cell receptor signaling, blockade or engagement of co-receptors (e.g., PD-1/PD-L1 inhibitors enhance T-cell cytotoxicity), modulation of T-cell activation or exhaustion