Fig. 3

High-magnification photomicrographs of hippocampal sections immunolabeled for tau from representative CTE stage II, III, and IV contact-sport cases. a–c Photomicrographs of AT8-positive neurons show intense, confluent labeling (black arrows) or puncta (white arrows) in hippocampal CA1 of stage II (a), III (b), and IV (c). d–f Photomicrographs of AT8-positive neurite clusters within CA1 from stage II (d) and IV (e) and CA3 hippocampal subfields from stage IV (f). g and h Example of a dystrophic fiber showing thorny excrescences in CA3 of a stage II case (g), and a non-dystrophic fiber with thorny excrescences in CA3 of a stage IV case (h). Thorny excrescences are distinct from artifacts seen with DAB/Ni processing [13]. i–k TauC3-immunolabeled CA1 neurons in stage II (i), III (j), and IV (k). Note the confluent deep labeling across the perikarya of neurons (black arrows). Scale bars = 10 μm in all panels. Roman numerals represent CTE stage