Daclizumab, 1 mg/kg of body weight, will be given for a total of 5 intravenous infusions to subjects diagnosed with moderate aplastic anemia (MAA), pure red cell aplasia (PRCA), Diamond Blackfan anemia (DBA), relapse and refractory severe aplastic anemia (SAA) will receive treatment. The Diamond Blackfan anemia arm was closed due to the lack of accrual. The hematologic response will be evaluated at 3 months. A complete hematologic response will be considered an achievement of normal blood counts. A partial response was defined as any response less than a complete response. The primary endpoint was a hematologic response in at least one affected peripheral blood count parameter, as determined by 3 separate measurements in the first 12 weeks after completion of the infusion.