Effect of panned phage 7-mer peptides on inhibition of anti–GPIIIa49-66–induced platelet fragmentation. (Left) First 3 bars refer to effect of patient Ab (Pt) on platelet fragmentation compared to buffer (C) or control IgG (Ci). Phage peptides were diluted at ratios of 1:3, 1:10, 1:30, and 1:100 and then preincubated with Ab for 15 minutes prior to the addition of the combined reagents to gel-filtered platelets. First bar is buffer diluent alone. Ab-induced platelet fragmentation was about 50% inhibited with a 1:100 dilution of the 3 phage peptides. (Right) Irrelevant peptide control phage (C1 and C2) as well as inhibitory phage peptides (H20R1, PHC39, PHC34) were diluted from 1:3 to 1000, preincubated with Ab as in the left panel, and then incubated with gel-filtered platelets. Data are representative of 2 different experiments.