There was a strong negative correlation between the number of p75NTR, but not TrkA-positive PCs and APP/Aβ plaque load in AD (r = −0.923, p = 0.0000002), but not in DS (r = 0.35, p = 0.2) or across groups (r = −0.37, p = 0.06). The gene discussed is APP; the disease is Alzheimer disease.