Fig. 1

NAb detection assay. A Complexes form between the fixed amount of added drug and NAb; the formation of these complexes allows SULFO-TAG–labeled PD-L1 to bind to biotinylated PD-1, which can bind to the streptavidin-ECL plate. B In the absence of NAb, the fixed amount of drug added to the solution binds to biotinylated PD-1 and prevents its interaction with PD-L1. SULFO-TAG–labeled PD-L1 bound to PD-1 is necessary to generate the ECL signal. ECL, electrochemiluminescence; NAb, neutralizing antibody; PD-1, programmed death 1; PD-L1, programmed death ligand 1