In human MCI and AD retinas, we identify a Chlamydia pneumoniae-Aβ42–linked NLRP3 inflammasome axis: NLRP3, ASC, and caspase-1 correlate strongly with retinal Chlamydia pneumoniae load and Aβ42, and associate with CCasp3 apoptosis, NGSDMD pyroptosis, retinal and brain atrophy, higher Braak stage, and worse MMSE. The gene discussed is PYCARD; the disease is Alzheimer disease.