Purification and kinetic studies on a circulating anticoagulant in a suspected case of lupus erythematosus.

A circulating anticoagulant in a suspected case of lupus erythematosus has been highly purified by a combination of Sephadex gel filtration and DEAE cellulose chromatography. The inhibitor is a gamma globulin with a sedimentation coefficient of 6.6 Svedberg units. For its anticoagulant action, the lupus inhibitor requires a co-factor which is present both in the lupus and normal blood. The cofactor is located in the gamma globulins fraction which is relatively heat stable, but less than the inhibitor, at 56 degrees C. The active lupus inhibitor (inhibitor + cofactor) is not species specific against human prothrombin. Working with highly purified systems, the active inhibitor is found to inhibit prothrombin conversion by formed prothrombin activator. It does not appear to inhibit the formation of prothrombin activator nor does it affect purified prothrombin.