Figure 6.

Type I and II IFN signaling mediates structural and functional damage to BM CARc networks. (A) Maximum-intensity projection of representative images of femoral bones of mice 14 dpi with LCMV-cl13 treated with PBS, a-IFNAR alone, or a-IFNAR and anti-IFNγ. Top: Green, CXCL12-GFP (CARc); scale bar, 200 µm. Middle: Color-coded tissue maps of CARc densities. Scale bar, 200 µm. Bottom: High-resolution images of zoomed-in regions depicting CARc in green and collagen IV ECM fibers in red. Scale bar, 50 µm. (B) 3D QM–based quantification of CARc density in BM tissues from uninfected (ctrl) and LCMV-cl13–infected mice (black bars) treated with a-IFNAR (red bars) or a combination of a-IFNAR and a-IFNγ (blue bars) 7 and 14 dpi (n = 3–9 samples from at least two independent experiments). (C and D) RT-qPCR of sorted BM CARc for Cxcl12 (C) and Scf (D) gene expression as percentage of HRPT expression (n = 3) for the same experimental groups as in B. (E and F) Protein concentrations of CXCL12 (E) and SCF (F) in BM extracts from one hind leg (femur + tibia; n = 3). (G and H) Absolute numbers of Lin⁻c-kit⁺ cells (G) and HSCs (H) in mice in all experimental groups 14 dpi (six mice, two independent experiments). (I and J) Quantification and representative dot plots of cell cycle analyses of HSCs as measured by staining for DAPI and Ki67 after infection with LCMV-cl13 of mice treated with IFN-blocking antibodies. Statistics were analyzed using two-tailed Mann–Whitney U test with *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, P > 0.05.