Competition binding for WP. The binding affinity of each test article for WP was compared with HRP-mLL1 in a competition ELISA using plates coated with WP. Concentrations of 2L-Rap-hLL1-γ4P (▪), hLL1-γ4P (♦), hLL1 (•), and hLL2 (▾) were plotted against absorbance at 490 nM.