Frozen floating tissue was processed for immunohistochemistry by incubation with antibodies against phosphorylated tau and immune cell reactivity using AT8 (a monoclonal antibody recognizing AD-related phosphorylation at Ser202/Thr205 on human tau protein) and CD68 (monoclonal antibody binding to the corresponding lysosomal receptor of macrophages) respectively. The gene discussed is CD68; the disease is Alzheimer disease.