Recombinant Human CTLA-4/CD152 Protein (C-His)

Measured by functional ELISA. Immobilized recombinant human CTLA-4 binds recombinant human CD80 with an EC50 in the range of 30–100 ng/mL; the binding is blocked by reference anti-CTLA-4 antibodies.

CTLA-4 (cytotoxic T-lymphocyte-associated protein 4, CD152) is an inhibitory receptor of the CD28 family and the founding member of the immune checkpoint class. Primarily expressed on regulatory T cells (Tregs) and transiently on activated conventional T cells, CTLA-4 shares its ligands CD80 (B7-1) and CD86 (B7-2) with the costimulatory receptor CD28, but binds them with substantially higher affinity. By competitively sequestering CD80/CD86 and delivering cell-intrinsic inhibitory signals, CTLA-4 raises the threshold for T cell priming in lymphoid organs and anchors Treg-mediated immune suppression. The anti-CTLA-4 antibodies ipilimumab and tremelimumab release this brake and have demonstrated durable survival benefit in melanoma and other cancers, and CTLA-4–Ig fusions (abatacept, belatacept) are used as immunosuppressants in autoimmune disease and transplantation. Recombinant human CTLA-4 supports bispecific and checkpoint-inhibitor screening, CD80/CD86 competition assays, and pharmacodynamic assay development.