Monoclonal antibodies to von Willebrand's factor: reactivity with porcine and human antigens

Monoclonal antibodies to porcine von Willebrand's factor (vWf) were obtained from hybridomas derived from the fusion of NS-1 plasmacytoma cells and spleen cells from immunized BALB/c mice. Twenty hybrids were positive in a radioimmunoassay based on the ability of immobilized hybridoma antibodies to bind porcine vWf as detected by the subsequent binding of 125I-polyclonal rabbit anti-vWf. Growth of the hybridomas as ascitic tumors yielded fluids having titers in this assay ranging from 8 x 10(7) to 8 x 10(11). All the antibodies were positive when normal, but not von Willebrand's, plasma was used as the source fo antigen in this RIA, and when normal, but not von Willebrand's, acetone-fixed platelets were used in an indirect immunofluorescence assay. Two of these antibodies inhibited both ristocetin-induced platelet aggregation and platelet aggregating factor. In a second radioimmunoassay, only 13 were of the 20 antibodies were reactive with human vWf, and two of these would not react with human antigen in the presence of 2M Nacl. Bases on these assays, six reactivity groups of antibodies could be identified.