TABLE 1.

Immunohistochemical Methods Tested

	Primary Antibody	Epitope Exposure	Signal Development
Nantes	p-synuclein monoclonal MJF-R13 (8-8) ab168381 Abcam* 1:10 000 (17)	Leica†, Proteinase K for 15 minutes (Bond Enzyme Pretreatment Kit)	Leica†, peroxidase blocking with Bond Enzyme Pretreatment Kit; mixed DAB Refine
RICM	a-synuclein monoclonal 5C12 (41) Prothena‡ 1 µg/mL	Ventana§ Protease 1 36°C, 12 minutes	Ventana Benchmark Ultra§; Optiview DAB IHC Detection Kit

^*Abcam, Cambridge, UK.

^†Leica Biosystems, Kassel, Germany.

^‡Prothena Biosciences, Dublin, Ireland.

^§Ventana Medical Systems, Tucson, Arizona.

p-synuclein = α-synuclein phosphorylated at serine 129; a-synuclein = α-synuclein unmodified form; DAB = 3,3′ di-aminobenzidine. All slides were counterstained with hematoxylin. See Supplementary Data Materials for full description.