Inhibition of binding of MoAb 7E3 to VNRC3 cells (A) and resting platelets (B) by echistatin and its analogues. The VNRC3 cells (5 × 10⁵) were preincubated with echistatin (○), D27W echistatin (•), echistatin 1-41 (▿), or R24A echistatin (▾) at room temperature for 15 minutes and then 7E3 (1 μg per sample) was added. Samples with platelets (6 × 10⁶ per sample) were prepared in similar manner except for the washing steps. The flow cytometry analysis was performed with FITC-conjugated goat antimouse IgG as described in the Materials and Methods. Error bars represent the standard deviation for three independent experiments.