CTLA-4 Blockade Bioassay

The CTLA-4 Blockade Bioassay reflects the mechanism of action (MOA) of biologics designed to block the interaction of CTLA-4 with its ligands, CD80 and CD86. The assay consists of two genetically engineered cell lines: CTLA-4 Effector Cells: 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: 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 Negative Cells and Control Ab, Anti-CTLA-4, are available separately.