American Society of Hematology

Figure 2.

$Transient T-cell depletion restores long-term multilineage engraftment after neonatal transplantation. (A) Experimental design. Mice were injected at 3 developmental stages: before birth at 14 DPC to model early-gestation IUHCT, after birth at 20 DPC to model late-gestation IUHCT, and in adulthood at 6 weeks of age to model postnatal HSC transplantation (HSCT). TCD BM harvested from B6GFP donors was injected alone or in combination with T cell–depleting antibodies (either anti-CD3, anti-CD4, or anti-CD8 mAbs). (B) Comparison of engraftment and prevalence of CD4+ T cells in uninjected littermates. “Engrafted” was defined as chimerism >1% at 24 weeks after injection. All the litters included in this study had sufficient circulating T cells to reject the allograft (ie, exceeded the threshold of immunocompetence). (C) Kaplan-Meier curve of persistent alloengraftment. The fraction of injected animals with chimerism >1% at each time point is shown. Injection of TCD BM + anti-CD3 mAb at 20 DPC results in sustained alloengraftment at 6 months in all animals, comparable with that observed after injection of TCD BM only at 14 DPC. (D) PB donor cell chimerism over time. The trajectory and magnitude of chimerism were equal between mice injected at 20 DPC with TCD BM + anti-CD3 mAb and 14 DPC with TCD BM only. (E) Quantitative T-cell recovery. Mice injected at 20 DPC with TCD BM + anti-CD3 mAb demonstrated T-cell recovery to levels comparable with those in uninjected controls at 3 weeks of age. Dual-lineage (host- and donor-derived) T-cell recovery was observed. (F) Multilineage analysis. Donor cell engraftment was observed among BM LSK cells (a population enriched for HSCs), with reconstitution of all leukocyte lineages, including T cells, B cells, monocytes, and macrophages. Comparable engraftment and multilineage reconstitution were observed between mice injected at 20 DPC with TCD BM + anti-CD3 mAb and mice injected at 14 DPC with TCD BM only. Mice injected at 20 DPC with TCD BM + anti-CD3 mAb demonstrated no signs of GVHD, as demonstrated by normal weight gain (G), phenotype scores (H), and hematoxylin and eosin (H&E) histology of GVHD-prone organs captured at 10× original magnification (I). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001.$

Transient T-cell depletion restores long-term multilineage engraftment after neonatal transplantation. (A) Experimental design. Mice were injected at 3 developmental stages: before birth at 14 DPC to model early-gestation IUHCT, after birth at 20 DPC to model late-gestation IUHCT, and in adulthood at 6 weeks of age to model postnatal HSC transplantation (HSCT). TCD BM harvested from B6^GFP donors was injected alone or in combination with T cell–depleting antibodies (either anti-CD3, anti-CD4, or anti-CD8 mAbs). (B) Comparison of engraftment and prevalence of CD4⁺ T cells in uninjected littermates. “Engrafted” was defined as chimerism >1% at 24 weeks after injection. All the litters included in this study had sufficient circulating T cells to reject the allograft (ie, exceeded the threshold of immunocompetence). (C) Kaplan-Meier curve of persistent alloengraftment. The fraction of injected animals with chimerism >1% at each time point is shown. Injection of TCD BM + anti-CD3 mAb at 20 DPC results in sustained alloengraftment at 6 months in all animals, comparable with that observed after injection of TCD BM only at 14 DPC. (D) PB donor cell chimerism over time. The trajectory and magnitude of chimerism were equal between mice injected at 20 DPC with TCD BM + anti-CD3 mAb and 14 DPC with TCD BM only. (E) Quantitative T-cell recovery. Mice injected at 20 DPC with TCD BM + anti-CD3 mAb demonstrated T-cell recovery to levels comparable with those in uninjected controls at 3 weeks of age. Dual-lineage (host- and donor-derived) T-cell recovery was observed. (F) Multilineage analysis. Donor cell engraftment was observed among BM LSK cells (a population enriched for HSCs), with reconstitution of all leukocyte lineages, including T cells, B cells, monocytes, and macrophages. Comparable engraftment and multilineage reconstitution were observed between mice injected at 20 DPC with TCD BM + anti-CD3 mAb and mice injected at 14 DPC with TCD BM only. Mice injected at 20 DPC with TCD BM + anti-CD3 mAb demonstrated no signs of GVHD, as demonstrated by normal weight gain (G), phenotype scores (H), and hematoxylin and eosin (H&E) histology of GVHD-prone organs captured at 10× original magnification (I). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001.

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