VWF multimer analysis of the metalloprotease proteolysis of target vWF induced by samples from patients with various thrombocytopenic disorders and control samples.

These 2 multimer gels represent the analysis of the vWF protease activity in some of the samples tested. After promoting digestion, the amount of vWF protease activity was determined by comparing the height of each individual multimer column to the target vWF (on the left of each gel), which represents 0 proteolysis. Following the metalloprotease activation assay, a decrease in the large-molecular-weight forms of the target vWF indicated normal vWF protease activity, and these samples were given scores of 3+ or 4+. The normal pooled serum (NP) demonstrated normal proteolysis. The addition of EDTA to the normal pool (NP + EDTA) prior to enzyme activation inhibited the protease activity and showed reduced protease activity with scores of 1+ or 2+. Target vWF, vWF plus normal pool, and vWF plus normal pool with added EDTA were run on each gel as standards. Some TTP samples (TTP 1, 2, 3, 5) had reduced vWF protease activity (1+ to 2+). Other samples from TTP patients (TTP 4 and 6) had normal vWF protease activity (3+ to 4+) and were indistinguishable from control or normal samples. Samples from patients with other thrombocytopenic disorders (ITP 1, 2, 3 and SLE 1) also had reduced vWF protease activity.