Gelatinase activity of matrix metalloproteinase (MMP)-2 (72 kDa) and MMP-9 (92 kDa) in sera of patients with systemic sclerosis (SSc) and healthy controls. Sera (0.5 μl) from 20 patients with SSc and 10 healthy controls were analyzed for their MMP-2 and MMP-9 activities by gel zymography. As a positive control, supernatants from cultured HT1080 cell lines (HT) stimulated with 10 μg/ml of concanavalin A were used. Numbers in parentheses are MMP-9 concentrations (ng/ml) determined by ELISA. The figure shows representative results for serum samples from the two groups.