Immunoprecipitation analysis of allele-specific recombinant GPIa isoforms. Recombinant forms of GPIa/IIa complex were produced in CHO cells transfected either with Glu₅₀₅Thr₇₉₉ (left panel), Glu₅₀Met₇₉₉ (middle panel), or Lys₅₀₅Thr₇₉₉ (right panel) form of GPIa. After surface labeling with biotin, cell lysates were immunoprecipitated with anti-Br^b (lanes 1), anti-Sit^a (lanes 2), and anti-Br^a (lanes 3). Immunoprecipitates were analyzed on 7.5% SDS-PAGE under nonreduced conditions, transferred onto nitrocellulose membrane, and visualized using chemiluminescence substrate.