XXXX - and @entity5126 platelet antibodies can react with @entity1427 /IIIa.

@entity1 @entity3742 @entity4463 @entity4807 @entity5126 @entity17432 @entity1427 @entity1428 @entity1422
@entity4807 - and @entity5126 -dependent antiplatelet antibodies are generally believed to bind to the membrane glycoprotein complex, GPIb/IX. However, we and others have found that some drug-dependent antibodies bind to platelets from @entity1 with the @entity3742 which lack these glycoproteins. We therefore studied the reactions of a group of these antibodies with normal and @entity3742 platelets and their membrane proteins. As indicated by rosette formation of the sensitized platelets around protein A-Sepharose beads, two @entity4807 - and two @entity5126 -dependent antibodies reacted with both normal and @entity3742 platelets at a high (300 microM) concentration of drug. At a pharmacologic drug concentration (10 microM), all four antibodies reacted with normal platelets but only the two @entity4807 -induced antibodies reacted with @entity3742 platelets. Immunoprecipitation studies with solubilized, @entity4463 -labelled normal platelets, at both high and low drug concentrations, showed that each of the four antibodies precipitated proteins corresponding to GPIb and @entity17432 . Fainter bands corresponding to glycoproteins IIb and IIIa, which do not label well with @entity4463 , were also detected. With radioiodinated normal platelets, it was found that each of the four antibodies was capable of precipitating @entity1427 /IIIa, but only in the presence of drug. The four antibodies also promoted drug-dependent precipitation of @entity1427 and @entity1428 from lysates of radioiodinated @entity3742 platelets. The two @entity4807 -dependent antibodies precipitated these glycoproteins at both high and low drug concentrations, while the @entity5126 -dependent antibodies reacted much more strongly at the higher drug concentration. Precipitation of GPIb/IX was not observed with BSS platelets. Absorption of a @entity4807 -induced antibody with @entity3742 platelets in the presence of drug eliminated its ability to precipitate @entity1427 and @entity1428 . However, the absorbed antibody retained the ability to precipitate GPIb from solubilized normal platelets. Thus, at least two drug-dependent antibodies were present, one specific for GPIb/IX and the other for @entity1427 /IIIa. These findings indicate that @entity1422 , in addition to the GPIb/IX complex, can serve as targets for drug-dependent antibodies in both intact and detergent-solubilized platelet preparations.
