MoAb VP-1 decreased proteolytic cleavage of the R834W vWF mutant. Autoradiograph of a 1.5% SDS agarose gel showing the size distribution of the vWF mutant incubated with TBS (lane 1) or the plasma proteinase after treatment, respectively, with 1/10 TBS (lane 2), VP-1 (lane 3), M13 (lane 4), or M31 (lane 5).