Fig. 2

PD-L1 expression was specifically and transiently induced in astrocytes in TBI mice. Cortex sections of the brains from sham mice (a, a1) and TBI mice at different timepoints of post-injury, 24 h (b, b1), 72 h (c, c1), 1w (d, d1) and 2w (e, e1) were stained with antibodies against PD-L1 (red) and GFAP (green for astrocytes). Enlarged single cell images of the c1–f (f1–3) and d1–g (g1–3) as highlighted by the white box showed the co-localization of PD-L1 with GFAP in reactive astrocytes. h–j, low power image of IHC staining of the brain tissue sections with antibodies against PD-L1 (red) and different neural cell type specific markers (green) including NeuN (neurons), Iba1 (microglia), and NG2 (oligodendrocyte progenitor cells or OPCs). DAPI (blue) was used for counter staining nucleus in these IHC analyses. High power images showed no PD-L1 expression was detected in either Neuron (h1–3), reactive microglia (i1–3), or OPCs (j1–3)