Researchers have shown that the tumor-secreted protein cystatin C crosses the blood-brain barrier in mice. This protein stimulates microglia to degrade amyloid plaques. Amyloid is a sticky protein linked to the development of Alzheimer's disease. Cystatin C binds to harmful amyloid clumps and activates the brain's immune cells. When the researchers blocked this mechanism in laboratory mice, the protective effect was lost. The research comes from the University of Toronto after fifteen years of study. The discovery opens up possibilities for translational clinical studies.