Fig. 3

Distribution of PD-L1-positive reactive astrocytes in the brain. The brain sections from mice at different timepoints of post-TBI were subjected to IHC staining with DAPI (blue) and Abs against PD-L1 (red) and GFAP (green). A a The schematic of sampling images at different positions from edge of cavity in cortex (b = 200 μm, c = 800 μm, and d = 1600 μm). A b–d The representative images of PD-L1 (red), GFAP (green), and DAPI (blue) labeled reactive astrocytes at different positions shown in a). B Percentage of PD-L1⁺GFAP⁺ double positive astrocytes in total GFAP⁺ reactive astrocytes at different positions from edge of cavity in cortex. Data showed the gradual decrease of percentage of PD-L1⁺GFAP⁺ astrocytes away from the edge of cavity (n = 5, *p < 0.05, **p < 0.01). C Representative images of PD-L1⁺ astrocytes that composed a dense zone surrounding the cavity of the cortex, where the glia scar was forming (1-week post-TBI). D Sporadic PD-L1⁺ reactive astrocytes were also found in the hippocampus underneath the injured cortex of TBI mice, but not sham mice