Cytotoxic T-lymphocyte-associated protein 4 is an immune checkpoint inhibitory receptor expressed on T cells and plays an important role in downregulating immune responses. The CTLA-4 Blockade Bioassay is a biologically relevant MOA-based assay that can be used to measure potency and stability of antibodies and other biologics designed to block the CTLA-4 interaction. The assay consists of two genetically engineered cell lines: CTLA-4 Effector Cells are Jurkat T cells expressing human CTLA-4 and a luciferase reporter driven by a native promoter that responds to TCR/CD28 activation; aAPC/Raji Cells are Raji cells expressing an engineered cell surface protein designed to activate cognate TCRs in an antigen-independent manner and endogenously expressing CTLA-4 ligands CD80 and CD86. When the two cell types are co-cultured, CTLA-4 competes with CD28 for their shared ligands, CD80 and CD86, and thus inhibits CD28 pathway activation and promoter-mediated luminescence. Addition of an anti-CTLA-4 antibody blocks the interaction of CTLA-4 with its ligands CD80 and CD86 and results in promoter-mediated luminescence. CTLA-4 Blockade Bioassay, Propagation Model, allows propagation and banking of the CTLA-4 Effector Cells. Bio-Glo Luciferase Assay System (Cat.# G7940, G7941) is the required reagent for use with this product.
