Characterization of PiB Binding to White Matter in Alzheimer Disease and Other Dementias

IHC and IF analysis indicates PiB staining does not bind to white matter. Microscopy images of 2 serial sections (7 μm) from frontal cortex of AD patient (A) and centrum semiovale from age-matched HC (B) and AD patient (C). First section was immunostained with antibody to Aβ (1E8) to identify Aβ plaques; second serial section was stained with 100 μM PiB. Presence of Aβ plaques was detected in AD frontal cortex sections (black arrowheads) and colocalized with positive PiB staining (white arrowheads). Centrum semiovale sections exhibited no immunoreactivity with 1E8, indicating absence of plaques (B and C). At higher magnification, PiB staining was observed to highlight blood vessels. (D) Serial sections (5 μm) isolated from gray matter (frontal cortex; top) and white matter (centrum semiovale; bottom) of patient with DLB who underwent ¹¹C-PiB PET 23 mo before his death. Sections (from left to right) were stained with antibodies to Aβ (1E8) to Aβ plaques, PiB, α-syn (97/8), and tau-protein (Dako) and stained with PiB (100 μM). Presence of Aβ plaques was detected in DLB frontal cortex sections and colocalized with positive PiB staining. Centrum semiovale sections exhibited no immunoreactivity with any reagent used, indicating absence of Aβ plaques, Lewy bodies, or neurofibrillary tangles. Images were taken on Leica microscope. Scale bars, 50 μm. α-syn = α-synuclein.