CTLA-4/CD28 (CTLA-4 (also known as CD152) and CD28)

CTLA-4 and CD28 are co-regulatory receptors that play opposing roles in T-cell signaling[1][2][3]. Both receptors bind to the same ligands (CD80 and CD86) on antigen-presenting cells but transmit opposite signals - CD28 provides stimulatory co-signals essential for T-cell activation, while CTLA-4 transmits inhibitory signals that downregulate T-cell responses[1][2]. CTLA-4 has higher binding affinity for these ligands and can outcompete CD28, effectively acting as an immune checkpoint to prevent excessive T-cell activation and maintain immune homeostasis[2][3]. CD28 is constitutively expressed on T-cells, while CTLA-4 expression is induced following T-cell activation[1]. CTLA-4 is particularly important in regulatory T-cells where it contributes to their suppressive function[3]. Both receptors are members of the immunoglobulin superfamily with similar structural features but distinct intracellular signaling domains that determine their opposing functional roles[1][2]. CTLA-4 has become an important therapeutic target in cancer immunotherapy, with checkpoint inhibitors like ipilimumab blocking CTLA-4 to enhance anti-tumor immune responses[3].

Other names

CD152Cytotoxic T-lymphocyte antigen 4T-cell-specific surface glycoprotein CD28

Immune checkpoint inhibition (for CTLA-4 targeting drugs); T-cell activation enhancement; Blockade of inhibitory signaling