GFAP and Alzheimer disease: Given that in AD, activated astrocytes colocalize more readily with fibrillar amyloid plaques57 and increased GFAP expression has been found to correlate predominantly with the presence of solid Aβ plaques,14 these results could hint at an indirect amelioration of astrocytic reactivity by gantenerumab due to successful cerebral plaque removal and explain why the engagement of solanezumab with soluble amyloid remained without effect on GFAP.