Participants will have a medical history review and physical examination, including laboratory studies. If medically indicated, x-rays, consultations and biopsies (surgical removal of a small tissue sample) of affected organs will also be conducted. All patients will begin treatment with prednisone and cyclophosphamide daily. Those who improve on this regimen will reduce the prednisone gradually and continue with cyclophosphamide until their disease is in remission. While taking cyclophosphamide, patients must have blood and urine tests done every 1 to 2 weeks. Those who achieve disease remission will stop cyclophosphamide and start taking methotrexate once a week, usually by mouth but possibly by injection into the muscle or skin. Blood and urine tests will be conducted once a week for 4 weeks while the dosage is being adjusted and then once a month for the duration of treatment. Patients on methotrexate whose prednisone dose is reduced to 10 to 30 mg every other day will be randomly assigned either to receive or not receive daclizumab in addition to the methotrexate. Daclizumab is given intravenously (through a plastic tube inserted into a vein) the day after the randomization, then again in 2 weeks, 4 weeks, and once a month for 18 months.