Our results indicated that the scores of activated B cell, activated CD8 T cell, CD56 bright natural killer cell, effector memory CD8 T cell, eosinophil, immature B cell, macrophage, memory B cell, monocyte, myeloid derived suppressor cell, natural killer cell, natural killer T cell and type 17 T helper cell were significantly different between AD and healthy groups (p < 0.05), indicating that the level of immune cell infiltration might be altered in the hippocampus of AD patients. The gene discussed is CD8A; the disease is Alzheimer disease.