Inhibition of patient antibody binding to immobilized cardiolipin by preincubation of the corresponding purified cofactor (10 μg/mL) with increasing concentrations of cardiolipin containing liposomes (A) or fluid-phase LPS (B). Results are from a representative experiment. Patients no. 3 (□), 4 (○), 5 (•), and 6 (▵).