BINDING OF CARDIOLIPIN TO POLYSTYRENE BEADS - EVIDENCE FOR A LAMELLARPHASE ORIENTATION

The association of cardiolipin with polystyrene beads was studied usin g P-31-NMR and electron microscopy. In the presence and absence of fet al calf serum, cardiolipin appeared to bind to the polystyrene beads i n lamellar phase as assessed by P-31-NMR imaging. Electron microscopic analysis revealed an even coating of phospholipid about the beads wit h extensive micelle binding. Cardiolipin-coated beads challenged with ACA-positive sera followed by immunogold indicated antibody bound to m icelles associated with the bead. Studies conducted with ACA IgG purif ied from patient sera indicated that some ACA bound to CL beads in the absence of a source of ACA cofactor (i.e. gelatin-blocked beads), som e ACA required beta(2)-GPI for binding (i.e. no binding in the presenc e of beta(2)-GPI-depleted plasma), whereas other ACA which showed negl iglible binding with gelatin-blocked beads, showed enhanced binding in the presence of beta(2)-GPI-depleted plasma. The data indicate that: (1) cardiolipin binds to polystyrene beads in lamellar phase, (2) ACA bind to phospholipid micelles bound directly to the polystyrene beads, and (3) ACA differ between individuals displaying varying phospholipi d and phospholipid/cofactor substrate specificities.