Reactions of antibodies with intact platelets at various concentrations of Ca⁺⁺.

Values shown (ordinate) are expressed as a percentage of the maximum fluorescence intensity obtained under the experimental conditions shown on the abscissa and represent the average of triplicate determinations that did not differ from each other by more than 15%. Reactions of tirofiban-dependent antibodies are shown in panel A, and eptifibatide dependent antibodies are shown in panel B. No reactions were obtained in the absence of drug under any of the experimental conditions (not shown).