Characterisation of monoclonal antibodies to human factor X/Xa. Initial observations with a quantitative ELISA...

Monoclonal antibodies to human plasma factor X (FX) and factor Xa (FXa) have been developed using several modifications of previously described techniques. These include the use of footpad immunisation with a suspension of free and nitrocellulose-bound antigen with subsequent fusion of popliteal lymph node cells. From a panel of 17 reactive hybridomas to FX, 3 were selected for further characterisation. An additional hybridoma reactive to FXa but not FX was also selected. Two monoclonal antibodies designated FX52 and FX64 were specific for FX with no reactivity to FXa, while antibody FXa24 was specific for FXa. Another FX/FXa95 reacted with both FX and FXa. All selected antibodies were of the IgG isotype and reacted both with native antigen and antigen transferred to nitrocellulose by Western blotting. Initial observations suggest that Mab FX52 may be used to quantitate FX levels in plasma.