Cardiolipin liposomes: A novel flow reagent for detection of anticardiolipin antibodies

The association of autoantibodies with specificity for phospholipids and an increased risk for thromboembolic phenomena has received considerable recent clinical attention. These autoantibodies have been reported in patients with defined autoimmune disorders as well as in patients with no other obvious autoimmune disease symptoms other than isolated or recurrent thromboembolic disease. A significant component of this autoimmune response appears to be related to cardiolipin‐directed antibodies. Most studies reported to date have used either an enzyme immunoassay or a radioimmunoassay for detection and quantitation of antiphospholipid antibodies. We have developed a novel flow cytometric assay for detection of anticardiolipin antibodies. The assay, by analogy to polystyrene microsphere assay, utilizes cardiolipin liposomes as solid‐phase microspheres for antigen presentation. In comparison to enzyme‐linked immunosorbent assay, the flow assay shows similar sensitivity by serum titration, has immunoglobulin class specificity, and is semiquantitative as currently designed. The flow assay is relatively easy to perform and should allow detection of other antiphospholipid specificities with tailoring of the phospholipid makeup of the liposomes.