Confocal microscopy of prosaposin localization on plaques and different cell types. (a-c). Aβ (green) (a) and PSAP (red) plaque (b) with limited colocalization (C – yellow) in an AD case. Scale bar represents 30 μm. (d-f). Comparison of colocalization in plaque of PGRN (green) and Aβ (blue) (d) with PSAP (red) and Aβ (blue) in triple-stained AD section. Merged images show extensive colocalization of PGRN and PSAP (yellow) but limited overlap with Aβ-positive structures. Scale bar represents 30 μm. (G-I). Merged images of PSAP (red) immunoreactivity with microglial markers IBA-1 (g) and CD68 (h) (green) and astrocyte marker GFAP (green) show some expression of PSAP in both cell types (yellow). These images show that PSAP (red) is predominantly in cells with morphology of neurons. Scale bar represents 10 μm. (j-l). Merged images of CD68 (green) and PSAP (red) on plaques in low plaque case (J), high plaque case (k) and AD case (l). Significant amounts of PSAP immunoreactivity (red) can be observed on all plaques but with only limited colocalization with CD68 in infiltrating microglia. Scale bar represents 30 μm. (m-n) Merged images of AT180 (pTau) (green) and PSAP (red) on tangle in low plaque case (M), high plaque case (n) and Alzheimer’s disease case (o). Very limited amounts of PSAP immunoreactivity (yellow) can be observed on tangles. Panel M and N show intracellular tangles with DAPI-positive nuclei, while panel O shows extracellular tangle. Scale bar represents 30 μm.