TSPO and early-onset autosomal dominant Alzheimer disease: Increased binding of ligands selective for TSPO has been observed at sites of central nervous system (CNS) pathology, such as glioma 162, 165, 166, 179, multiple sclerosis 21 as well as Alzheimer's disease (AD) 38, and TSPO ligand binding is now seen as a hallmark for microglial activation in vivo.