A monoclonal antibody to VIII:C produced by a mouse hybridoma.

Spleen cells of a BALB/c mouse immunized with factor VIII procoagulant activity (VIII:C) (isolated by affinity chromatography) were fused with mouse myeloma cells (P3 x 63 Ag8). After the fusion 12/32 wells produced an inhibitor to VIII:C. Cells from one well (1B3) were subcloned four times in order to isolate the hybridoma that produces the anti-VIII:C antibody. Injection of hybridoma cells in pristane pretreated BALB/c mice results in anti-VIII:C titers of 5000-10,000 Bethesda U/ml. Analysis of the produced immunoglobulin demonstrated heavy chains of IgG1 (produced by the myeloma cell line) and IgG2b subclass. The 1B3 antibody neutralizes VIII:C in LMW FVIII, crysosupernatant, cryoprecipitate, and normal plasma. It was found that binding of the IgG to FVIII results in a delay in its activation and not in an inhibition of its cofactor activity. The antibody removes VIII:C from pooled normal plasma when coupled to Sepharose; when coupled to plastic tubes, it binds VIIICAG from isolated VIII:C, purified FVIII, and pooled normal plasma; it does not bind VIIIR:AG, fibrogen, or serum VIIICAG. The 1B3 antibody can be used successfully in an IRMA for VIIICAG.