LPS binds dose-dependently to PF4. Binding of biotinylated LPS (0.6, 1.3, 2.5, 5.0, 10, 20, and 40 μg/mL) to immobilized PF4 (10 μg/mL) was detected with peroxidase-conjugated streptavidin, followed by the addition of tetramethylbenzidine. Binding of PF4 to BSA or buffer (each with 10 μg/mL) served as controls to exclude nonspecific binding of LPS-biotin to proteins or to the plastic surface. Data are mean OD₄₅₀ ± SD of 3 independent experiments.