KLK8 and Alzheimer disease: Exploring CSF KLK8 levels in middle-aged and aging subjects who are cognitively normal, suffering from subjective memory complaint, from MCI, and from AD (early and late-onset type) may help elucidate KLK8’s broader role, much as CSF studies have been valuable in understanding ratios of phosophorylated τ to total τ, and Aβ42/Aβ40 ratios in AD.