The activated CD4+ T cells, central memory CD8+ T cells, Th17 cells, MDSCs, and Treg cells were significantly enriched in AD patient's serum, while the central memory CD4+ T cells, effector memory CD8+ T cells, Th1 cells, Th2 cells, γδT cells, macrophages, and NK cells were significantly reduced in AD patient's serum. The gene discussed is CD4; the disease is Alzheimer disease.