Based on the increase of pro-inflammatory cytokines and Th subsets found in AD brains, this study assesses the proportions of CD8+CD3−IL-17A+IFNγ− Th17 cells, CD8+CD3−IL-17A−IFNγ+ Th1 cells, and CD4+CD127lowCD25+ Tregs in cryopreserved PBMCs of subjects with Alzheimer’s dementia (AD dementia), MCI due to AD (MCIAD), MCI unlikely due to AD (MCIother), and subjects without cognitive impairment (controls). The gene discussed is CD4; the disease is Alzheimer disease.