GRN and Alzheimer disease: The features of PGRN-positive plaques in low plaque, high plaque and Alzheimer’s disease cases revealed that most of the deposits of PGRN around plaques appeared extracellular, and even though cell membranes are not visible in the sections, most PGRN immunoreactivity was not clearly associated with nucleated cells (Fig. 4 panels L, P, T).