Figure 4. Bone marrow DC ablation induces vascular endothelium permeability and expansion in the bone marrow.

(A, B) Representative photomicrographs of femur sections from Zbtb46^dtr bone marrow chimeras treated with PBS (left), 1 day of DT (1D-DT, middle) or 6 days of DT (6D-DT, right). (A) FITC-conjugated bovine serum albumin (BSA) was injected intravenously into mice 15 minutes before sacrifice. Sections were imaged for FITC-BSA (green) and VE-cadherin⁺/CD31⁺ endothelial cells (red). (B) Sections were imaged for VE-cadherin⁺/CD31⁺ endothelial cells (red) and counterstained with DAPI to highlight nuclei (blue). Original magnification, ×200. (C) The ratio of extravascular FITC-BSA to intravascular FITC-BSA was quantified and normalized to the PBS-treated cohort (n = 9, 8, 7 mice). (D, E) Histomorphometry (D) (n = 9, 8, 7 mice) or flow cytometry (E) (n = 4 or 6 mice) was used to quantify endothelium or endothelial cells in the bone marrow; endothelial cells were identified by flow cytometry as lineage^– (CD45, Ter119, Gr-1) CD31⁺ cells. Data are mean ± SEM. *P < 0.05; **P < 0.01 compared with PBS-treated mice. Significance was determined using an ANOVA with Tukey’s Honest Significant Difference post hoc analysis for C and D, or an unpaired Student’s t test for E.