Double-IF for Ctsz and CD68 showed co-expression of Ctsz in CD68+ lysosomal structures of sizes up to 4–5 μm (Figure 9A), thereby being of the same size as the large vacuole-like structures observed in the processes of some of Iba1+ microglial cells in some of the AD brains (Figure 9B). Here, CTSZ is linked to Alzheimer disease.