CTLA-4 blockade primarily acts during T-cell priming in the lymph node by preventing CTLA-4 from outcompeting CD28 for B7 ligand binding, resulting in enhanced T-cell activation. PD-1 blockade acts in the tumor microenvironment by preventing PD-L1/PD-L2-mediated exhaustion of effector T cells. The two mechanisms are complementary, which is why combination CTLA-4 + PD-1 therapy (Ipilimumab + Nivolumab) shows synergistic clinical efficacy in several tumor types.

CTLA-4-Fc chimera is recommended for blocking assays because the Fc domain provides bivalent binding that mimics native CTLA-4 homodimer avidity. Use it together with recombinant CD80 or CD86 protein to set up competitive binding assays or reporter gene blockade assays. For SPR kinetics where monovalent affinity is needed, use His-tagged CTLA-4 ECD instead.

Yes. We offer a research-grade Ipilimumab biosimilar (anti-human CTLA-4, IgG1 subclass) produced in CHO cells. It is suitable for use as a positive control in CTLA-4 binding assays, as a reference standard in bioanalytical method development, and for analytical comparability studies. It is RUO only and not intended for therapeutic use.

Yes. CTLA-4 is constitutively expressed in the intracellular compartment of Tregs and is only transiently expressed on the cell surface upon activation. For intracellular staining, fix and permeabilize cells first, then stain with a fluorochrome-conjugated anti-CTLA-4 antibody. For surface staining on activated T cells, stimulate cells with anti-CD3/CD28 for 24-48 hours before staining.

A typical assay uses CTLA-4-expressing Jurkat-NFAT-Luc reporter cells co-cultured with CD80-expressing CHO antigen-presenting cells. CTLA-4 engagement suppresses NFAT-driven luciferase signal; adding an anti-CTLA-4 blocking antibody releases the inhibition, producing a dose-dependent increase in luminescence. Use our recombinant CTLA-4 protein as a calibrator and Ipilimumab biosimilar as a positive control.