Microglial state shifts reveal resilience mechanisms in Alzheimer's disease

Researchers have identified six distinct tissue domains spanning an Alzheimer's disease pathological continuum, pinpointing a critical inflection point where amyloid-β–driven inflammation transitions to tau-associated cellular programs. At this threshold, microglia—resident brain immune cells responsible for pathogen defense, senescent cell clearance, and tissue maintenance—shift from early inflammatory phenotypes to late antigen-presenting states, termed early and late plaque-induced gene (PIG) programs. Analysis of octogenarians with and without dementia, plus cognitively intact centenarians bearing comparable amyloid burden via spatial transcriptomics and single-nucleus RNA sequencing of superior frontal cortex, revealed that resilience emerges through divergent mechanisms: cognitively intact octogenarians lacked late PIG activation entirely, while centenarians showed late PIG engagement decoupled from tau accumulation. These findings reframe Alzheimer's not as inevitable pathology but as a dynamic process where microglial state transitions at the amyloid-tau interface function as candidate resilience points with direct therapeutic relevance for future interventions.