Combined Effects of Interleukin-7 and Stem Cell Factor Administration on Lymphopoiesis after Murine Bone Marrow Transplantation

The decreased ability of the thymus to generate T cells after bone marrow transplantation (BMT) is a clinically significant problem. Interleukin (IL)-7 and stem cell factor (SCF) induce proliferation, differentiation, and survival of thymocytes. Although previous studies have shown that administration of recombinant human IL-7 (rhIL-7) after murine and human BMT improves thymopoiesis and immune function, whether administration of SCF exerts similar effects is unclear. To evaluate independent or combinatorial effects of IL-7 and SCF in post-BMT thymopoiesis, bone marrow (BM)-derived mesenchymal stem cells transduced ex vivo with the rhIL-7 or murine SCF (mSCF) genes were cotransplanted with T cell–depleted BM cells into lethally irradiated mice. Although rhIL-7 and mSCF each improved immune reconstitution, the combination treatment had a significantly greater effect than either cytokine alone. Moreover, the combination treatment significantly increased donor-derived common lymphoid progenitors (CLPs) in BM, suggesting that transplanted CLPs expand more rapidly in response to IL-7 and SCF and may promote immune reconstitution. Our findings demonstrate that IL-7 and SCF might be therapeutically useful for enhancing de novo T cell development. Furthermore, combination therapy may allow the administration of lower doses of IL-7, thereby decreasing the likelihood of IL-7–mediated expansion of mature T cells

Prevention of graft-versus-host disease by anti–IL-7Rα antibody

Graft-versus-host disease (GVHD) continues to be a serious complication that limits the success of allogeneic bone marrow transplantation (BMT). Using IL-7–deficient murine models, we have previously shown that IL-7 is necessary for the pathogenesis of GVHD. In the present study, we determined whether GVHD could be prevented by antibody-mediated blockade of IL-7 receptor α (IL-7Rα) signaling. C57/BL6 (H2Kb) recipient mice were lethally irradiated and underwent cotransplantation with T-cell–depleted (TCD) BM and lymph node (LN) cells from allogeneic BALB/c (H2Kd) donor mice. Following transplantation, the allogeneic BMT recipients were injected weekly with either anti–IL-7Rα antibody (100 μg per mouse per week) or PBS for 4 weeks. Anti–IL-7Rα antibody treatment significantly decreased GVHD-related morbidity and mortality compared with placebo (30% to 80%). IL-7Rα blockade resulted in the reduction of donor CD4+ or CD8+ T cells in the periphery by day 30 after transplantation. Paradoxically, the inhibition of GVHD by anti–IL-7Rα antibody treatment resulted in improved long-term thymic and immune function. Blockade of IL-7R by anti–IL-7Rα antibody resulted in elimination of alloreactive T cells, prevention of GVHD, and improvement of donor T-cell reconstitution