T cell costimulatory molecules

T cell costimulatory molecules are cell-surface proteins, primarily transmembrane glycoproteins, that deliver positive (stimulatory) or negative (inhibitory) signals to T cells in the context of antigen presentation. These signals are required alongside T cell receptor (TCR) stimulation to drive full T cell activation, proliferation, survival, and differentiation. Costimulatory signaling is fundamental for the proper development and function of effector, memory, and regulatory T-cell subsets. The most prominent examples include the CD28, CTLA-4 (CD152), ICOS (Inducible Co-stimulator), PD-1, CD40, and members of the TNF receptor superfamily such as OX40, 4-1BB, and CD27[2][5][6][8]. T cell costimulatory molecules are a family of cell-surface proteins (including CD28, CTLA-4, ICOS, PD-1, OX40, CD40, and several others) crucial to controlling T cell activation, function, and differentiation. These molecules, belonging mainly to the immunoglobulin and TNF receptor superfamilies, serve as both activators and inhibitors of T cell immunity. Therapeutic targeting of these molecules underpins modern immunotherapies for cancer, autoimmunity, and transplantation, but the umbrella term refers to a group/family, not a discrete molecule or receptor[1][6][8].

Other names

T cell co-stimulatory receptorsT cell costimulation moleculesCo-signaling receptors (including both stimulatory and inhibitory molecules)

Blockade of negative costimulatory signals (immune checkpoint inhibition, e.g., anti-CTLA-4, anti-PD-1). Blockade of positive costimulatory signals (e.g., inhibition of CD28 signal with CTLA-4 fusion proteins). Agonism of positive stimulatory receptors (e.g., OX40, 4-1BB, CD40 agonists enhance T cell activity). Dual modulation (some strategies co-target multiple members for improved efficacy).