Fig. 2

α-Synuclein fibril exposure in the midbrain induces a rapid innate immune response. a Immunohistochemisty for SYN1 (α-synuclein, NiDAB-black) to label injected α-synuclein fibrils 6, 24, or 72 hours post-fibril injection, as indicated. Brain regions are depicted as follows: SNpc, substantia nigra pars compacta, VTA, ventral tegmental area, SNr, substantia nigra pars reticulata. b Fluorescent immunohistochemistry depicting α-synuclein fibril spread (SYN-1, blue color) and microglial localization (IBA-1, green color) in the ipsilateral SNpc (highlighted with dashed white/blue lines) with TH as red color, 24 hours post injection. Confocal image, Scale bar is 0.2 mm. c Immunohistochemistry depicting inflammation in the ipsilateral SNpc of saline, d monomer, or e fibril-injected rats, 24-hours post injection. Representative individual channels (depicted in grayscale for clarity) and merged images are shown (merged is MHCII-green, IBA-1-blue, TH-red). Scale bar is 150 μm. d Immunohistochemistry depicting inflammation in the ipsilateral SNpc of monomer injected rats, 24 hours post injection. Individual channels and merged confocal images are shown (MHCII-green, IBA-1-blue, TH-red). e Immunohistochemistry depicting inflammation in the ipsilateral SNpc of α-synuclein fibril injected rats, 24 hours post injection. Individual channels and merged confocal images are shown (MHCII-green, IBA-1-blue, TH-red). f Immunohistochemistry depicting peripheral CD163+ myeloid infiltration and inflammation in the ipsilateral SNpc of saline, g monomer, or h fibril-injected rats, 24 hours post injection. Representative confocal images are shown for CD163 staining that is outside the vasculature (i.e., perivascular CD163+ macrophages are not shown). CD163 is green color, IBA-1-blue color, TH-red color. Scale bar is 150 μm. Images are representative of at least three rats analyzed per group