Immunochemical characterization of platelet‐specific alloantigens

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Abstract
Immunoprecipitation was performed with platelet-specific alloantisera (anti-Zwa, -Zwb, -Baka and antiserum Luc) and 125I-labeled platelets of a panel of donors typed for these platelet-specific alloantigens. This was done by sensitization of intact, radiolabeled platelets with the antisera, solubilization of the sensitized platelets with Nonidet P-40 and recovery of the immune complexes from the lysate with heat-killed, formalin-fixed Staphylococcus aureus, strain Cowan I. In the case of platelet antibodies of the IgM class, bacteria also preincubated with rabbit-IgG anti-human IgM before treatment of the lysate were applied. Radiolabeled antigens were then eluted from the bacteria by boiling in an SDS[sodium dodecyl sulfate]-mercaptoethanol-containing buffer. Subsequently, the eluted antigens were analyzed by SDS-polyacrylamide gel electrophoresis. Both the Zwa and Baka antigens are located on the glycoprotein-IIb/IIIa complex. The location of the Zwb antigen could not be established in this way. From the intensity of the precipitated glycoprotein bands, it appeared that Zwa is probably a marker of glycoprotein IIIa, Baka or glycoprotein IIb. Immunoprecipitates of anti-Zwa and anti-Baka sera both carried, to some extent, complexes of glycoproteins IIb and IIIa. Iodinated platelets of a Glanzmann thrombasthenia patient failed to show any material precipitated by these antisera or the antisera Luc, known to contain antibodies against both glycoproteins.