Abstract
This paper describes a quantitative assay for the binding ability of plasma factor VII to human tissue factor (TF) on microplate. Plasma samples from eight patients with congenital factor VII abnormality were measured by this method. The procedure is simple for using recombinant TF from commercial prothrombin time reagent, and non isotopic for using anti-factor VII IgG labeled biotin. Its sensitivity to detect factor VII binding ability to tissue factor was about 3% of normal subjects. The factor VII-TF binding ability was inhibited by monoclonal anti-TF antibody that is characterized by its inhibition of interaction between factor VII and TF. Being partially detected immediately after the addition of the plasma sample on the wells of micro-plate coated with TF, the factor VII binding to TF had completely achieved in 2hr at 37°C or 8hr at 4°C. Measured factor VII binding ability to TF in normal subjects was 101.17±18.90% (X±SD), and the value correlated well both with factor VII activity (r=0.788) and antigen (r=0.662). Two homozygous subjects with the mutation of Arg 79 to Gln in factor VII (Human Molecular Genetics, 2: 1335, 1994) had a half level of a normal subject for factor VII-TF binding. Two heterozygous subjects who are sons of the homozygous subjects had lower levels in the normal range as for factor VII-TF binding. One of 4 patients with congenital factor VII abnormality whose mutation site had not been detected yet, had 26% of normal subjects. Three of the 4 patients had the normal range as for factor VII-TF binding.
