EVALUATION OF IN-VIVO IMMUNE-COMPLEX FORMATION AND COMPLEMENT ACTIVATION IN PATIENTS RECEIVING INTRAVENOUS STREPTOKINASE

The usefulness of several different methods for detecting immune compl ex formation and complement activation in the circulation were applied to samples from patients receiving intravenous Streptokinase therapy for myocardial infarction. Streptokinase is a foreign antigen and can cause immune reactions. We collected samples from 13 patients, before Streptokinase administration (baseline), at the end of infusion (1 h), 12 h later and on day 7. We measured IgG containing immune complexes (IgG-IC), free C3d and antibodies to Streptokinase by ELISA, and CR1, C3d and C4d on erythrocytes by flow cytometric assay. Antibodies to St reptokinase are common, as all but two of the patients had measurable antibody levels. During Streptokinase treatment there was a drop in an tibody levels, most prominent in those patients who had high baseline levels. At the same time increased levels of free C3d and erythrocyte- bound C3d were observed. After 12 h free C3d was usually back to basel ine level, but C3d on erythrocytes was still raised. These data indica te the formation of Streptokinase immune complexes in patients with hi gh Streptokinase antibody levels, and show that these complexes are cl eared rapidly from the circulation, leaving more persistent signs of c omplement activation. We conclude that free C3d is a good indicator of ongoing complement activation, whereas C3d on erythrocytes indicates that complement activation has recently taken place.