Conversion of αIIbβ3 to the high-affinity state does not circumvent dependence on disulfide-exchange–induced thiol expression for binding of fibrinogen and change in conformation.
Platelets were incubated with activating antibody anti-LIBS6 in the presence of FITC-fibrinogen (squares), monoclonal antibody PAC-1 (diamonds), or FITC–anti-mouse IgG (triangles) and of increasing concentrations of pCMPS (A), bacitracin (B), or RL90 (C). The total fluorescence at each concentration of inhibitor was expressed as the percentage of fluorescence in the absence of inhibitor, defined as 100%. Data are mean ± SD from 3 different determinations using samples from 3 different donors. Concomitant determination of bound FITC-fibrinogen and PAC-1 induced by anti-LIBS6, as well as of bound anti-LIBS6 itself, showed that direct activation of αIIbβ3 is not sufficient for thiol-dependent ligation of the receptor.
