CHARACTERIZATION OF AN ACQUIRED IGG INHIBITOR OF COAGULATION-FACTOR-XIII IN A PATIENT WITH SYSTEMIC LUPUS-ERYTHEMATOSUS

An acquired IgG inhibitor to factor XIII was identified in a 30-year-o ld Vietnamese woman with systemic lupus erythematosus. The Ig fraction was isolated from plasma by chromatography on an agarose gel column a nd by protein G adsorption. The anti-factor XIII activity, identified within the IgG fraction, inhibited factor XIII from both normal plasma (a(2)b(2)) and platelets (a(2)). A normal level of the b subunit was measured by immunoelectrophoresis of the patient's plasma, but the a s ubunit was not detected. These results suggested the presence of an Ig G immunoglobulin which recognized the a subunit and interfered with it s activity.