After allogeneic bone marrow transplantation, T cell recovery is impaired for some time. This can lead to infections and even relapse. Memorial Sloan-Kettering medical oncologists Marcel van den Brink, Miguel-Angel Perales, and colleagues report on a phase I trial in which recombinant human interleukin-7 (CYT107) administered following T cell-depleted allogeneic stem cell transplantation significantly boosts the reconstitution of functional T cells. In the study, patients who had allogeneic stem cell transplantation as treatment for myeloid cancers (AML, CML, MDS) and who received a weekly subcutaneous injection of CYT107 for three weeks experienced a doubling in CD4+ and CD8+ T cells. The T cells were also found to be functional against cytomegalovirus in patients with that infection. Moreover, CYT107 was associated with few side effects. These results indicate that CYT107 can safely and quickly enhance immune recovery after T cell-depleted allogeneic stem cell transplantation without causing serious toxicity. The findings were published in the December 6, 2012, issue of the journal Blood.