Aβ composition in primate brains. (A) Western blot analysis of Aβ oligomers in the membrane fraction of brain extracts from immunized (n = 10) and non-immunized aged non-human-primates (n = 6) using 6E10 antibody. The left lanes show human brain tissue samples without Alzheimer’s disease (AD), with mild cognitive impairment, and with AD for comparison. (B) Densitometric analysis showed a significant difference in the dimer to pentamer ratio in immunized compared with non-immunized aged animals. Bars represent mean ± SD.