In clinics spanning Britain, Israel, and the Netherlands, forty people in the early stages of Alzheimer's disease became the first human test of an idea that has quietly challenged neuroscience for decades: that the aging immune system, not merely the plaques it fails to clear, lies at the heart of the disease. The experimental antibody IBC-Ab002, born from years of research at the Weizmann Institute, proved safe at every dose and left measurable traces of biological benefit in those who received it. It is a modest beginning, as all first steps in medicine must be, but it signals that the long