REGIMEN - During the induction phase, subjects will receive 2 cycles of subcutaneous rhIL-7 dosed once weekly for 3 weeks in a dose escalation fashion: 3 microg/kg (first 3 subjects-completed), 10 microg/kg (next 5 subjects-completed) and 20 microg/kg (last 5 subjects), with an additional 5 subjects at the highest achieved dose level. Cycles of rhIL-7 will be administered starting at Week 1 and Week 24.