Binding of fibrinogen and expression of the ligand-induced conformation depend on disulfide-exchange–induced expression of free thiols and on PDI.

(A) Concentration-dependent effect of pCMPS, bacitracin, and RL90 on binding of FITC-fibrinogen to platelets in autologous plasma stimulated by ADP (diamonds), collagen (squares), thrombin (triangles), and CRP-XL (circles). The total fluorescence at each concentration of the inhibitor was expressed as the percentage of fluorescence in its absence, defined as 100%. Binding in the presence of the inhibitors is shown in solid lines, and binding in the presence of IgG_2aascites (a control for the effect of RL90 in ascites) is shown in dotted lines. Data are mean ± SD from 3 different determinations using samples from 3 different donors. (B) Binding of FITC-conjugated PAC-1 under the same conditions as in panel A. (C) Binding of monoclonal PMI-1, followed by FITC-conjugated anti-mouse IgG, under the same conditions as in panel A.