Effects of IFN blockage on the BM and HSCs of infected and non-infected mice. (A–E) Quantification of total BM cells (A), Ter119⁺ erythroid progenitors (B), B220⁺ cells (C), Lin⁻c-kit⁺ progenitor cells (D), and LSKCD48⁻CD150⁺ cells (E) in mice after infection and blockage with either a-IFNAR or a-IFNγ (n = 5–7 mice from two independent experiments). Statistics were analyzed using Mann–Whitney U test with *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, P > 0.05. (F) Image-based quantification of CARc densities in the BM of mice 7 and 14 dpi with LCMV-cl13 in untreated and a-IFNγ–treated mice (n = 3–4 mice, two experiments). (G) Blockade of IFNAR does not impact cell cycle entry of HSCs without LCMV-cl13 infection. Dot plots showing representative cell cycle analyses of HSCs (LSKCD48⁻CD150⁺) using DNA labeling (DAPI) and immunostaining against Ki-67. HSCs were isolated 7 d after injection with either PBS or a-IFNAR antibody. (H) Quantification of cell cycle analyses, n = 3 mice. Statistics were analyzed by Mann–Whitney test. (I and J) Limiting-dilution transplantations of 10, 20, 50, and 100 HSCs (LSKCD48⁻CD150⁺) from control untreated mice (CTRL) and mice treated with a-IFNAR and a-IFNγ for 56 d. (I and J) Calculation of functional repopulating HSCs (I) and engraftment levels and lineage distribution (J) of donor-derived CD45-1⁺ cells in transplanted mice (n = 4–5 mice per group). (K) Quantification of divisional (div) history of CFSE-labeled IFNγR^−/− LSKCD48⁻CD150⁺ HSCs after transplantation into control and LCMV-cl13–infected (56 dpi) mice (n = 5–6 recipient mice from two independent experiments). Statistics were analyzed by two-tailed Mann–Whitney U test with *, P < 0.05; ns, P > 0.05.