S100B and early-onset autosomal dominant Alzheimer disease: S100B is abundantly found in astrocytes, is elevated in the CSF of those with Alzheimer’s disease and is considered a marker of acute neural distress that is neuroprotective at nanomolar concentrations and neurotoxic at micromolar levels.55,92 In our study, CSF S100B concentrations were in the nanomolar range, and although these are not tissue concentrations, they are suggestive of neurotrophic astroglial activity.