Kinetics of inhibition of FVIII activity by patient LE inhibitor. Total IgG of patient LE (•) diluted to an inhibitory activity of 10 BU/mL was incubated at 37°C with normal plasma as a source of FVIII. Residual FVIII activity was determined in a one-step coagulation test after various incubation times. As a comparison, 10 BU/mL of total IgG prepared from patient BO, a patient with severe hemophilia and a high titer inhibitor, was included (○).