The Binding Activity of PD-1 with anti-PD-1 antibody. Activity: Measured by its binding ability in a functional ELISA. Immobilized Human PD-1(CSB-MP619964HU1) at 2 μg/mL can bind Anti-PD-1 recombinant antibody, the EC<sub>50</sub> is 1.960-3.961 ng/mL.