The epitopes of PA anti-αIIbβ3 Abs are mainly localized in the N-terminus of the β-propeller domain of αIIb. (A) Binding of PA Abs to normal (black) or αIIbβ3-deficient platelets (GT platelets; white). C1 and C2 show control eluates. (B) Binding of PA Abs to 293T cells that expressed human (black) or mouse αIIbβ3 (white; left). Expression levels of human and mouse αIIbβ3 were indicated in the right panel monitored by anti-CD61 Ab. (C) Relative binding of PA Abs to 293T cells that expressed mouse αIIb/human β3 (m2b/H3a; black) or human αIIb/mouse β3 (H2b/m3a; white) compared with human αIIbβ3-expressing cells. (D) Relative binding of PA Abs to 293T cells that expressed human αIIb replaced with whole β-propeller domain (white) or the N-terminus to W4:4-1 loop (black) of mouse αIIb with human β3. (E) Relative binding of PA Abs to 293T cells that expressed mouse αIIb replaced with whole β-propeller domain (white) or the N-terminus to W4:4-1 loop (black) of human αIIb with human β3. Shown were means of ≥ 2 independent experiments.