Growth hormone accelerates immune recovery following allogeneic T-cell–depleted bone marrow transplantation in mice

Objective To test in a murine model whether recombinant human growth hormone can promote immune recovery after allogeneic T-cell–depleted bone marrow transplantation. Materials and Methods Lethally irradiated (8.5 Gy) BALB/c mice (H2d) were transplanted with 5×106 T cell–depleted bone marrow cells from C57BL/6 mice (H2b). Recipient mice were injected intraperitoneally with recombinant human growth hormone (20 μg/dose/day) or saline for the first 4 weeks after transplantation. These animals were followed for phenotypic and functional immune recovery. Results Administration of human recombinant growth hormone improved the CD4+ T-cell counts in peripheral blood on day +14 (44±14 vs 33±7/μL blood, p<0.05) and day +21 (281±109 vs 187±76/μL blood, p<0.01) compared with the saline control. These differences were no longer significant by day +28 despite continued growth hormone administration. Similar effects were also observed on CD8+ T cells and B220+ B cells. The improvements in peripheral T-cell counts were at least partially as a result of enhanced thymopoiesis because there was an increase in total thymocytes after treatment with growth hormone. T-cell–depleted bone marrow recipients treated with growth hormone rejected the third-party grafts faster than those treated with saline control (median survival time: 20 days vs 26 days, p<0.05). Conclusions These data demonstrated that recombinant human growth hormone can accelerate phenotypic and functional immune reconstitution following allogeneic T-cell–depleted bone marrow transplantation in mice.