Effects of antibodies: reaction on gel filtered platelets ability to bind ¹²⁵I-HK. ¹²⁵I-HK (9 nmol/L) binding to gel-filtered platelets was monitored after incubating for 30 minutes with the MoAbs AK-1, AK-2, AK-3, and FMC-25 or the protein ligands echicetin and bovine vWF (all additions at 1.68 μmol/L). The total binding defined as 100% was that observed in the absence of antibody or ligand. The results are the mean ± SEM of two experiments in quadruplicate. The differences are statistically significant (P < .0005), except for AK-3, compared with ¹²⁵I-HK binding alone.