Activity of quinine-dependent thrombocytopenia patient sera against mouse platelets. Patient sera were used in flow cytometry experiments to examine whether the reaction against human and mouse platelets could be distinguished. Figure is representative of the reaction of patient sera against human and mouse platelets. AB type sera, an isotype-matched IgG, and patient sera in the absence of quinine were used as negative controls (solid gray peak). Open histograms: dotted line indicates mouse platelets without quinine; dotted and dashed line, mouse platelets with quinine; thin solid line, human platelets without quinine; and thick solid line, human platelets with quinine.