Fig. 4

Bone marrow cells transplanted from chronic TBI mice reprogram host innate immune function in the absence of the brain injury environment. (A) Using a novel bone marrow transplantation approach, sham and 90 days post-injury (dpi) donor cells were transplanted into irradiated, congenic WT recipients. Femur bone marrow cells were harvested from 90 dpi and sham congenic Pepboy (CD45.1) donor mice, and 100 ml of BM cells (1 × 10⁶ cells/mouse) were intravenously injected by retroorbital injection in recipient WT (CD45.1) C57BL/6 mice. Mice were allowed to reconstitute for 8 weeks following transplantation. WT naïve (non-irradiated) mice were sex- and age-matched to both chimera groups. (B-D) Blood donor cells (CD45.1, B-C) and leukocyte (CD45+, D) were counted using flow cytometry. n = 5–6 mice/group. (E-G) Circulating and bone marrow-derived Ly6G + neutrophils from TBI→WT chimeric mice exhibited reductions in 0.5–1.0 mm Red Beads + cells and increase in the mean fluorescence intensity (MFI) of DHR123 + ROS. Left panels of E-F are representative dot plots. n = 5–6 mice/group. (H-I) Bone marrow-derived Ly6G + neutrophils from TBI→WT chimeric mice showed significant reductions in TNF and IL-1b production. Left panels of H are representative dot plots of TNF + cells. n = 7 mice/group. For all histograms, light gray = fluorescence minus one (FMO) control. Data were analyzed using one-way ANOVA group analysis with Tukey’s test for multiple comparisons (E-G) or Student’s T-test for two group comparisons (H-I). ****P < 0.0001, **p < 0.01, *p < 0.05. SH: Sham, WT wildtype