Western blot analysis of expressed WT and mutant GPIbα. Cell lysate, conditioned medium of 293T transfected cells, and plasma from the patient and his brother were immunoprecipitated with MBC 142.2, analyzed simultaneously by SDS-PAGE on a 6% gel, and immunoblotted with MBC 142.6. The immunoprecipitate of the brother's PPP was diluted 1:25, and the patient's PPP was diluted 1:2. Purified glycocalicin 0.38 ng was analyzed on this gel simultaneously.