CD68 and supranuclear palsy, progressive, 1: To confirm that TSPO radioligand binding determined with PET in PSP reflects microglial reactivity, we assessed the regional association between histologically determined microgliosis in post-mortem brain tissue and 11C-PK11195 binding potential (BPND) from the same PSP donors during life.8,10 ‘Phagocytic’ microglia were quantified using CD68 immunohistochemistry across eight cortical and 11 subcortical regions.