In this study, using the optimal diagnostic LASSO model, we identified eight feature genes as biomarkers of AD: ATP2B3, BDNF, DVL2, ITGA10, SLC6A12, SMAD4, SST, and TPI1. We further identified high infiltration of DCs and pDCs as playing a vital role in the immunology of AD. This evidence concerns the gene SMAD4 and Alzheimer disease.