WT does not affect the total levels of α_IIbβ₃ , but inhibits the activation state of α_IIbβ₃ . Primary megakaryocytic (A) and HEL (B) cells were preincubated with 100 nmol/L WT, 1 mmol/L RGDS or RGES peptides, or vehicle buffer (TPO alone) for 2 hours at 37°C and stained with anti-CD41a MoAb, PAC1 MoAb, or FITC-fibrinogen. Staining was assessed by FACScan, as described in Materials and Methods. Data are expressed as means ± SD of three to six separate experiments.