Coimmunoprecipitation of apo(a)/Lp(a) with β-2 glycoprotein I from human plasma. Immunoprecipitates were formed in plasma by using two different polyclonal (pAB1, pAB2) and two different monoclonal (F7, F10) antibodies raised against β-2 glycoprotein I or nonimmune serum, respectively. Immunodetection for the presence of apo(a) was performed using anti-apo(a) MoAb 1A2. Immunoprecipitation of apo(a) with the apo(a)-specific MoAb 1A2 served as positive control. The band seen at 50 kD represents the reduced IgG heavy chain.