It has been a growing puzzle in recent years that the posr mortem brains of individuals who had never shown any symptoms of Alzheimer’s when alive can be as full of plaques — amyloid-beta peptide — of anyone with the full-blown disease.
A paradigm shift was clearly required, but such are easier said than done. It took research into mice’s brains to bring it about. In the latter, it was discovered by researchers at Harvard and Massachusetts General Hospital that the amyloid-beta plaques were, in fact, protecting the brain against microbial attack, and not in any way harmful in themselves.
The amyloid-beta plaques are natural products of immune systems and send out fibrils in order to entangle and trap bacterial infections and prevent them proliferating. It would thus appear that something similar is going on in our case and is very much bound up with the immune systems we happen to be born with.
Years of further research will still be needed but it looks as though scientists will be on the right track now. We can fervently hope so.