Fig. 1

a–h Photomicrographs showing immunolabeling for CHI3L1 in the frontal cortex (FC) layers I–II, III–IV, and V–VI as well as WM in NCI, MCI, mAD, and sAD cases. Note CHI3L-ir cells appear mainly in layer I–II and WM in NCI, MCI, and mAD, while in sAD cells were also observed in layers III–IV and V–VI. Insets show high-power images of CHI3L-ir cells (arrows) in panels a–d, h, and i–p. q Graphic representation displaying the average numbers of CHI3L1-ir cells in the FC layers and WM in NCI, MCI, mAD, and sAD. Note the significantly higher numbers of CHI3L1-ir-positive cells in all FC layers and WM in sAD compared to NCI (p = 0.003). The tissue in a, e, i, and m panels were counterstained with Gill’s hematoxylin. Scale bar in panel p = 100 μm and inset = 10 μm, which applies to all other panels and insets in the figure. Abbreviations: NCI, no cognitive impairment; MCI, mild cognitive impairment; mAD, mild to moderate AD; sAD, severe AD