NPTN and Alzheimer disease: Moreover, the comparison of quantified neuroplastin immunoreactivity between two AD groups with a different disease duration (AD ≤ 4 years vs AD ≥5 years) revealed a significant decrease in Np immunoreactivity with disease progression in the dentate gyrus, CA2/3, and subiculum, (P = 0.014, 0.010, 0.011, respectively) (Figure 2D).