Interleukin-15 enhances immune reconstitution after allogeneic bone marrow transplantation

Interleukin-15 (IL-15) is a gamma-common cytokine that plays an important role in the development, survival, and proliferation of natural killer (NK), NK T and CD8(+) T-cells. We administered IL-15 to recipients of an allogeneic bone marrow transplantation (allo BMT) to determine its effects on immune reconstitution. Posttransplantation IL-15 administration significantly increased donor-derived CD8(+) T (mostly CD122(+)CD44(+)CD8(+) T-cells), NK, and NK T-cells at day +28 in young and old recipients of allo BMT This was associated with enhanced T-cell and NK-cell function. IL-15 stimulated homeostatic proliferation of donor CD8(+) T-cells in recipients of carboxyfluorescein diacetate succinimidyl ester-labeled donor T-cell infusions. Posttransplantation IL-15 administration also resulted in a decrease in apoptotic CD8(+) T-cells, an increase in Bcl-2-expressing CD8(+) T-cells, and an increase in the fraction of Ki67(+) proliferative NK and CD8(+) T-cells in recipients of allo BMT. IL-15 did not exacerbate graft-versus-host disease (GVHD) in recipients of T-cell-depleted BMT but could aggravate GVHD in some cases in recipients of a T-cell-repleted BMT. Finally, we found that IL-15 administration could enhance graft-versus-leukemia activity. In conclusion, IL-15 can be administered safety to recipients of a T-cell-depleted allo BMT to enhance CD8(+) T, NK, and NK T-cell reconstitution. (C) 2005 by The American Society of Hematology.