HPLC/SEC. PF4 alone (A) and β2GPI alone (B) were injected individually to a Superose 6 10/300 GL column connected to an ÄKTA HPLC system, at a flow rate 0.5 mL/min. Preincubated complexes (30 minutes at 37°C) consistent with PF4 + β2GPI (C) and PF4 + β2GPI + anti-β2GPI (D) were injected into the column as previously. (E) SEC-purified fractions from peaks 1 to 5 were concentrated in a SpeedVac and were analyzed by immunoblot with anti-PF4 mAb.