GFAP and Alzheimer disease: Astrogliosis was measured using glial fibrillary acidic protein (GFAP), an intermediate filament protein highly expressed by reactive astrocytes.19 Activated microglia/macrophages were measured using CD68, a glycoprotein highly expressed in the lysosomes of activated myeloid cells.20,21 We hypothesized that clinicopathologic heterogeneity measures and glial activation markers would differ among CLix-classified AD subtypes and provide further neurobiologic insight into selective vulnerability observed in AD brains.