Immunochemical Characterization of the Platelet - Specific Alloantigen Lek 5 : A Comparative Study With the l ’ ’ Alloantigen

We report the immunochemical characterization of a new platelet-specific alloantigen detected using an lgG antibody isolated from the serum of a patient with posttransfusion purpura (PTP). In indirect immunoprecipitation experiments, the antibody, termed anti Leka, predominantly precipitated glycoprotein (GP) llb from Triton X-100 lysates of normal human platelets. In an immunoblot procedure, which involved the transfer of platelet polypeptides separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to nitrocellulose membrane, anti Ieka bound exclusively to GP lIb. Under identical conditions, four anti PIAl antibodies each reacted with GP lIla. No binding of anti Ieka lgG occurred to leka ( ) platelets or to their separated polypeptides although GP lIb was normally