Representative binding curve of antibody to mammalian expressed human interferon beta 1a (circle) and to 0.1% BSA/PBS (square) in a Direct Binding ELISA. Medium-binding polystyrene plates were coated with either 1 µg/ml human interferon beta 1a or 0.1% BSA/PBS. Thereafter, titrations of the product were added to the wells. Donkey anti-mouse IgG conjugated to HRP was used as the detection antibody. Colorimetric detection was performed using 3,3',5,5'-Tetramethylbenzidine (TMB) substrate. The HRP-TMB reaction was stopped using a diluted H₂SO₄/HCl solution.