PYCARD and Brain atrophy: 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.