Binding and blocking activities of IMC-EB10. (A) Plates precoated with an anti-His antibody were incubated with His-tagged FLT3-Fc protein for 1 hour. After washing, titrated IMC-EB10 or control antibody IMC-C225 was added and incubated for 1 hour. Bound antibodies were measured in a biotin-streptavidin reaction with a microplate reader at OD_450nm. IMC-EB10 is shown to bind to the FLT3 receptor in a dose-dependent manner. (B) Antibody competition assay of ligand-receptor binding was performed in plates coated with FL. Mixtures of biotinylated FLT3 receptor (fixed amount) and antibody (titrated concentrations) were then added and incubated for 1 hour. FLT3 receptor bound to FL was measured in a biotin-streptavidin reaction with a microplate reader at OD_450nm. IMC-EB10 shows a strong blocking activity toward FL-FLT3 receptor binding. Error bars represent means ± SD.