Abnormal fibrinolytic activity in systemic lupus erythematosus and possible mechanisms

Plasma fibrinolytic activity was measured in 34 patients with systemic lupus erythematosus (SLE) and 12 normal subjects. Patients with SLE showed a significantly reduced resting level of plasma tissue plasminogen activator (t-PA) compared to normal. The reduction in t-PA was demonstrated both by a functional assay (fibrin-plate lysis, FP) and an immunochemical assay (ELISA). Measurement of the fibrinolytic response following venous occlusion allowed division of the patients into two groups. In the first (24 patients), there was a normal increase in t-PA response, demonstrated both by the functional and immunochemical assays. In the second (10 patients), there was a significantly reduced plasma t-PA response measured by FP. Seven of the patients in this second group, which included four patients with histological evidence of vasculitis, showed a similar failure of t-PA response (ELISA) after venous occlusion. These results suggest that their impaired fibrinolytic response may be related to defective t-PA release secondary to endothelial cell damage. The remaining three patients in the latter group had a normal t-PA (ELISA) response despite a reduced FP response, suggesting the presence of an inhibitor.