①Measured by its binding ability in a functional ELISA. Immobilized CD40 at 2 μg/ml can bind CD40L , the EC50 is 3.112-3.858 ng/ml.②Human CD40 protein hFc tag captured on COOH chip can bind Human CD40L protein hFc and Flag tag with an affinity constant of 2.06 nM as detected by LSPR Assay.