In vitro saturation binding assays of immunopurified PHF-tau from AD brain homogenates indicated a KD of 0.7 nM and Bmax of 310 pmol/mg [25], whereas autoradiographic studies of the frontal lobe from post mortem AD patients indicated a KD of 15 nM [140] and 14.6 nM [138] for PHF-tau. This evidence concerns the gene MAPT and Alzheimer disease.