Effect of continual LA IgGs on thrombin production in the phospholipid-coated flow reactor. Glass capillaries were coated with phospholipid vesicles and incubated with 0.1 μmol/L prothrombin, 0.1 nmol/L factor Va, and control or LA IgG for 1 hour. The concentration of LA IgG used in the experiment was that which resulted in maximal prothrombin binding (see Fig 5): 5 μmol/L for LA4 and LA7; 10 μmol/L for LA2, LA5, and LA6; 20 μmol/L for LA1; and 50 μmol/L for LA3. The capillaries were perfused with either 20 pmol/L factor Xa or 20 pmol/L factor Xa and LA IgG at a flow rate of 30 μL/min. Two-minute fractions were collected and the thrombin concentration was determined by the rate of hydrolysis of N-p-Tosyl-Gly-Pro-Arg-p-nitroanilide. Total thrombin production was calculated for each LA IgG and is expressed as a percentage of the mean control value for each IgG concentration (see Fig 5). Data points and error bars represent the mean and SE of 5 experiments. (▪) Results from perfusion with 20 pmol/L Xa alone; (□) results from perfusion with both 20 pmol/L Xa and LA IgG.