CD8A and Alzheimer disease: Research has implicated both the innate immune system and the adaptive immune system in the pathogenesis of AD, showing the increased recruitment of microglia toward the site of amyloid deposition [340], as well as increased CD8+ and CD3+ cells positively correlated with tau pathology [170,341] in the brain, while in the peripheral blood, patients with AD had decreased regulatory T cells (Tregs) and increased Th17 cells [342,343].