Patients with moderate-to-severe AD had significantly lower IgG (300 vs. 374 mg/dL; <i>p</i> < 0.001; r = -0.346), IgA (10 vs. 14 mg/dL; <i>p</i> = 0.004), and IgM (38 vs. 51 mg/dL; <i>p</i> = 0.001) levels when compared with those with mild disease. The gene discussed is CD79A; the disease is Alzheimer disease.