Examination of soluble Aβ species in AD brain extracts by several investigators has indicated that the neurotoxic activity resides primarily in the low molecular weight (LMW) fraction of AβO (dimers, trimers, tetramers, dodecamers), while high molecular weight (HMW) aggregates are largely inert, though they reportedly can dissociate into LMW species7,8,10,12,16,23. This evidence concerns the gene ABO and Alzheimer disease.