Participants will have a 15-minute infusion of daclizumab every 2 weeks for five doses. They will be seen by a physician at least once every 2 weeks while receiving the drug and then at weeks 12, 20, and 32 of the study. Blood will be drawn at the 4- and 8-week visits during treatment for diagnostic tests, and at each follow-up visit after treatment to assess the response to therapy.