At its core, the APOE–microglia axis involves bidirectional regulation between APOE proteins and microglia: microglia upregulate APOE expression in the AD pathological environment, while APOE proteins in turn shape microglial functional states, thereby influencing key AD pathological processes such as amyloid pathology, tau pathology, and neuroinflammation. This evidence concerns the gene APOE and amyloidosis.