Inhibition of PF4:heparin ULCs. (A) Dose response of antagonists for inhibition of ULC formation measured by ELISA. Data are the mean ± SEM of at least 3 independent experiments performed in triplicate. Curves represent fit of data to the indirect Hill equation. (B) Inhibition of ULCs as measured by gel filtration. Antagonists are at 1mM. Data are representative of 2 or more experiments. (C) Inhibition of ULCs by PF4As spans a wide range of heparin concentrations. Conditions are as in panel A, except that ULCs were formed with PF4 and various concentrations of heparin (0.05, 0.1, 0.2, 0.4, 0.8, and 1.6 U/mL from left to right in each group). (D) Incubation of KKO with PF4As (1mM) does not inhibit KKO binding to ULCs as measured by ELISA. Data are the mean ± SEM of at least 3 independent experiments performed in triplicate. (E) Dose response of antagonists for breakdown of preformed ULCs. Data are mean ± SEM of at least 3 independent experiments performed in triplicate. Concentrations of antagonists for each series (from right to left) are 2mM, 1mM, 500μM, and 250μM (125μM and 63μM for PF4A01 only).