ARM I: Patients begin therapy no later than 120 days after the first day of the last course of HiDAC treatment OR day 0 of PBSCT. Patients receive low-dose interleukin-2 (IL-2) SC on days 1-14, 19-28, 33-42, 47-56, 61-70, and 75-90. In addition, patients receive high-dose IL-2 SC on days 15-17, 29-31, 43-45, 57-59, and 71-73.