Costimulatory molecule

Costimulatory molecules are a heterogeneous group of cell-surface and transmembrane proteins expressed mainly on antigen-presenting cells such as dendritic cells and B cells; they provide essential secondary signals (beyond antigen recognition) required for full T cell activation, function, and fate decisions. Key families include the B7 family (CD80/B7-1, CD86/B7-2), TNF receptor/ligand family (e.g., CD40, OX40L), among others. These molecules can deliver either activating or inhibitory signals, thereby shaping immune responses towards activation (immunity), tolerance, or regulation, and are therefore important therapeutic targets in cancer, transplantation, and autoimmune diseases. However, “costimulatory molecules” is a collective term; further specification is required to reference an individual drug target molecule.

Other names

Costimulation moleculesCo-stimulatory moleculesSignal II molecules

Immune checkpoint inhibition or blockade (e.g., blocking CTLA-4 or PD-1/PD-L1 pathways); Costimulatory blockade (e.g., abatacept prevents costimulation of T cells by binding CD80/CD86); Modulation of T cell activation—either enhancing or suppressing immune responses