T cell checkpoint protein (null (No single abbreviation; individual checkpoint proteins have standard abbreviations such as CTLA-4, PD-1, LAG-3, TIM-3, etc.[6][8]))

T cell checkpoint proteins are a diverse group of transmembrane and glycoprotein receptors—or their ligands—expressed on T cells and other immune cells. They play a critical role in regulating the immune response by acting as molecular switches: some checkpoints (e.g., CD28, ICOS) stimulate T cell activation, while others (e.g., CTLA-4, PD-1, LAG-3, TIM-3, TIGIT, CD112R) deliver inhibitory signals that maintain peripheral tolerance, prevent autoimmunity, and restrict the magnitude and duration of immune responses. Many tumors exploit these inhibitory checkpoints to escape immune surveillance; as a result, drugs that block these proteins (checkpoint inhibitors) have become major cancer therapies. While checkpoint inhibition has revolutionized cancer treatment through reactivation of T cells, it introduces risks of immune-related toxicities. Precise molecular targeting—usually to specific checkpoint receptors—is necessary for clinical applications; hence, "T cell checkpoint proteins" is a functional family, not a single molecular entity[1][2][3][5][6][7][8][9][10].

Other names

Immune checkpoint proteinsT cell immune checkpointsInhibitory checkpoint moleculesCostimulatory checkpoint molecules (for stimulatory family members)[4][6][8][9]

Checkpoint inhibition: Blockade of checkpoint proteins prevents inhibitory signaling, “turning on” T cell immune responses against cancer and infected cells[1][5][6][7][9] Monoclonal antibody binding prevents interaction with partner ligands (e.g., PD-1/PD-L1, CTLA-4/CD80/86), disrupting “off” signals to T cells[5][6][9] Some drugs (agonists/antagonists) modulate stimulatory checkpoint proteins, enhancing T cell expansion and effector functions[4][10]