Multiple genetic variants associated with increased AD risks were found in immune-related genes including CD33, CR1, HLA-DRB5-HLA-DRB1, MEF2C, TREM2, and PLCG2. Neuropathologic analysis has commonly shown microglial activation in AD, and we and others previously showed stage-specific CSF alterations in complement and interleukin levels7–10. This evidence concerns the gene PLCG2 and Alzheimer disease.