During hospitalization, blood will be drawn daily for blood counts and other tests. Upon the patient's discharge after 10 days, the referring physician will do blood tests weekly during the first month of treatment and then every 2 weeks for the rest of the time the patient is taking cyclosporine. Dosages of this drug may be adjusted depending on the test results. Patients will be evaluated at the NIH Clinical Center at 3-month intervals for the first year, then every 6 months for the next 3 years and then at yearly intervals. A blood sample will be drawn at each visit. Bone marrow biopsies will be done at 6-month intervals for the first 3 years after treatment.