Programmed cell death protein 1 (PD-1), Cytotoxic T-lymphocyte–associated protein 4 (CTLA-4) (PD-1, CTLA-4)

T-cell activation inhibition is a biological process in which inhibitory receptors on T cells (most notably PD-1 and CTLA-4) transmit a signal that restrains T-cell activation, proliferation, and effector functions. Therapeutic targeting of these molecules is foundational in cancer immunotherapy, enabling the restoration of anti-tumor immunity by “releasing the brakes” on T cells. In autoimmune diseases and transplantation, enhancing the function of these checkpoints can prevent excessive or detrimental immune responses. The process is not a single molecular entity but involves multiple interacting receptors, signaling events, and downstream pathways, orchestrating immune balance and self-tolerance. For structured data or database purposes, “T-cell activation inhibition” should be mapped to specific molecular targets such as PD-1 (Programmed cell death protein 1) and CTLA-4 (Cytotoxic T-lymphocyte–associated protein 4), not treated as a receptor or molecule itself.

Other names

Immune checkpoint receptorsinhibitory receptorsiRsimmune regulators

Monoclonal antibodies block interaction of PD-1 or CTLA-4 with their ligands (PD-L1, CD80/CD86), releasing the inhibitory checkpoint, thereby restoring/enhancing T-cell activation and immune responses against tumors or down-tuning autoimmunity.