The resolution of platelet serologic problems using Western blotting

Serologic identification of anti‐PL^AI and other platelet specific antibodies is difficult because other platelet reactive antibodies (e.g. anti‐HLA) are commonly found in the samples. We have developed and evaluated a method using Western blotting to identify platelet specific antibodies. Since anti‐PL^AI is the most frequently encountered antibody, we used this antibody to validate the method. The PL^AI antigen was found on a 95,000 Dalton protein, confirmed as glycoprotein IIIa by two‐dimensional electrophoresis. The usefulness of Western blotting in resolving difficult platelet serologic problems was compared to a radiolabeled antiglobulin test using intact platelets. Our results showed that all sera with anti‐PL^AI identified by serology were confirmed by Western blotting. In addition, one anti‐PL^AI was detectable only by the proposed method. Western blotting was also as useful as a serologic method to PL^AI type platelets. HLA antibodies were not demonstrable by this technique. In summary, Western blotting is a highly specific and sensitive way of identifying anti‐PL^AI in a variety of clinical situations. This approach may be used to identify antibodies to other platelet specific antigens and to standardize platelet antigen typing sera.