MAPT and Alzheimer disease: METHODS: We measured AHR agonistic activity using a luciferase reporter assay in serum and cerebrospinal fluid (CSF) from 138 individuals (113 non-demented, 25 demented) classified by CSF Aβ1-42, Aβ1-42/Aβ1-40 ratio and pTau181 into four AT1 groups: A + T1 + (AD), A + T1- (isolated decrease of Aβ1-42/Aβ1-40 or Aβ1-42), A-T1 + (isolated tau pathology/PASSED), and A-T1- (biomarker-negative controls).