HUVECs were grown in the presence of 20% serum and treated with rhIL-11 or placebo for 3 hours or 72 hours. We measured vWf concentration in the culture supernatant of the treated cells using an ELISA technique as described in “Materials and methods.” Data from a representative experiment are shown for the 3-hour incubation, whereas the 72-hour incubation was performed in triplicate.