CD68 and early-onset autosomal dominant Alzheimer disease: Even in a chronic disease, such as Alzheimer's disease (Walker et al.,2002), in which uPAR positive staining is colocalized with CD68-positive macrophages, it is not clear whether these are resident or infiltrating cells, because bone marrow-derived infiltrating macrophages have been reported to be selectively targeted to amyloid plaques in animal models of Alzheimer's disease (Simard et al.,2006).