REACTIVITY TO BETA(2) GLYCOPROTEIN-I CLEARLY DIFFERENTIATES ANTICARDIOLIPIN ANTIBODIES FROM ANTIPHOSPHOLIPID SYNDROME AND SYPHILIS

Anticardiolipin antibodies (aCL) detected by standard ELISA are found in association with autoimmune and infectious diseases. It is now reco gnized that beta(2) glycoprotein I (beta(2)GPI) is a cofactor for aCL binding to cardiolipin (CL). To examine differences in cofactor requir ements, aCL positive sera from patients with the antiphospholipid synd rome (APS) and syphilis were studied. Using an ELISA with human purifi ed beta(2)GPI adsorbed onto irradiated plates, we detected high bindin g activity in 29 out of 35 samples from APS patients and low in only 1 out of 37 aCL positive syphilis sera. Moreover, a good correlation (r = 0.79) was also observed in the former group between aCL and anti be ta(2)GPI. Whole IgG and affinity purified IgG aCL from APS patients di d not bind to CL in the absence of beta(2)GPI, but recognized beta(2)G PI on irradiated plates in the absence of phospholipids. In contrast, IgG purified from syphilis patients only bound to CL alone. Taken toge ther, these data indicate that performing both ELISA (aCL and anti bet a(2)GPI) it could be possible to distinguish aCL from autoimmune or in fectious diseases.