Cytotoxic T-lymphocyte protein 4 (CTLA-4)–T-lymphocyte activation antigen CD80 interaction (CTLA-4–CD80 interaction)

The Cytotoxic T-lymphocyte protein 4 (CTLA-4)–T-lymphocyte activation antigen CD80 interaction is a critical inhibitory immune checkpoint that regulates the magnitude of T-cell responses and maintains peripheral tolerance. CD80 (also known as B7-1) is a ligand primarily expressed on professional antigen-presenting cells (APCs), while CTLA-4 is a receptor upregulated on T cells following activation and constitutively expressed on regulatory T cells (Tregs). CTLA-4 binds to CD80 with significantly higher affinity and avidity than the stimulatory receptor CD28, effectively outcompeting it for ligand binding and delivering inhibitory signals that lead to T-cell anergy or cell cycle arrest [1, 2, 8, 9]. Additionally, CTLA-4 can physically remove CD80 from the APC surface via trans-endocytosis, further limiting the availability of co-stimulatory signals for CD28 [10, 13]. In oncology, this interaction is targeted by monoclonal antibodies like ipilimumab, which block CTLA-4 to "release the brakes" on the immune system, enabling a robust anti-tumor T-cell response [4, 7]. Conversely, in autoimmune diseases and organ transplantation, the interaction is exploited using CTLA-4-Ig fusion proteins like abatacept and belatacept [2, 4, 12]. These drugs bind to CD80 on APCs to prevent its interaction with CD28, thereby suppressing unwanted T-cell activation and promoting immune tolerance [3, 4]. Therapeutic modulation of this pathway is highly effective but can lead to significant immune-related adverse events (irAEs), such as colitis and endocrinopathies, due to the systemic loss of self-tolerance [7, 8].

Other names

B7-1–CTLA-4 interactionCD80–CD152 interactionB7.1–CTLA-4 interactionCD80–CTLA4 interactionB7-1–CD152 interactionCD80–CTLA-4 interaction

Therapeutic agents either block the interaction to enhance anti-tumor immunity (checkpoint inhibitors) or mimic/utilize the interaction to suppress T-cell activation in autoimmunity and transplantation (CTLA-4-Ig fusion proteins).