JAK2-V617F HSCs need IL-1β for long-term stem cell function. (A) Schematic drawing of noncompetitive (1:0) transplantations. Primary recipients of VF;GFP or VF;IL-1β−/−;GFP BM were sacrificed at 36 weeks after transplantation and their BM cells (2 × 106) were transplanted into WT recipients (n = 18 per group). (B) The time course of blood counts from mice that received BM from VF;GFP (solid symbols) or VF;IL-1β−/−;GFP donors (open symbols), and their GFP chimerism in the peripheral blood (lower panel) are shown. (C) Analysis of GFP chimerism in HSPCs from the BM and spleen is shown. Multiple t tests were performed for statistical analyses. (D-F) Schematic drawing of the identical aforementioned experiment, in which BM competitor cells from a WT mouse was mixed to a 1:1 ratio for the transplantations into secondary WT recipients. Annotations as in panels B and C. Multiple t tests were performed for statistical analyses. (G) Bar graphs show the percentages of mice that showed engraftment defined as GFP chimerism of >1% at 18 weeks after noncompetitive (left) and competitive 1:1 transplantation (right). Middle panel shows the log of nonengrafted mice (GFP chimerism in Gr1 of <1% at 18 weeks) vs the number of donor BM cells transplanted in each group. Estimated frequency of functional stem cells in the BM was calculated using extreme limiting dilution analysis.34 Solid dark blue line represents the estimated frequency of HSCs in mice transplanted with BM from VF;GFP donors. Solid light blue line represents the estimated frequency of HSCs in mice transplanted with BM from VF;IL-1β−/−;GFP donors. Dotted lines show 95% confidence interval. Gray shaded areas represent the normal range. All data are presented as mean ± SEM; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; and ∗∗∗∗P < .0001. See also supplemental Figures 3 and 4.
