Multimeric analysis of plasma vWF in SDS-1% agarose gel. Equal amounts of vWF:Ag (0.0025 U vWF:Ag/lane) from four patients with chronic relapsing TTP (A1, A2, B, and C), from asymptomatic family members (A3, A4, and A5) and of pooled NHP were applied on top of the gel and the vWF multimers were detected by immunostaining. The double-sided arrow (↕) denotes the unusually large vWF multimers. Plasma samples from each patient were obtained on two separate occasions at dates given in Table 1.