Immunoprecipitation of GPIb-GPVI complexes is increased by treatment of platelets with convulxin. Washed human platelets (5 × 10⁸/mL) were resuspended in HEPES-saline buffer, pH 7.4, containing 10 mM EDTA, and treated with either 20 μg/mL CRP or collagen or 0.5 μg/mL convulxin for 60 minutes, then lysed in the same buffer containing Triton X-100 and proteinase inhibitors as described in “Materials and methods.” Platelet lysates were precleared, mixed with 10 μg/mL of either antiglycocalicin antibody or a nonimmune rabbit control antibody and immune complexes precipitated by mixing with protein A-Sepharose. After washing the beads, captured proteins were eluted in SDS sample loading buffer and analyzed for levels of GPVI by SDS-PAGE and immunoblotting using the anti-GPVI monoclonal antibody, 6B12-3. Blots were stripped and reprobed with the anti-GPIbα monoclonal antibody, WM23. Data are representative of at least 3 experiments with different donors. IP indicates immunoprecipitation; WB, Western blotting; NT, not treated; and NIR, nonimmune rabbit IgG.