Finally, we investigated the distribution of LOY in six types of sorted leukocytes—CD19 + B lymphocytes, CD4 + T lymphocytes, CD8 + T-cytotoxic lymphocytes, Natural Killer (NK) cells, granulocytes, and monocytes—among men diagnosed with Alzheimer’s disease (N = 121) or prostate cancer (N = 107) vs. healthy controls (N = 156). The gene discussed is CD19; the disease is Alzheimer disease.