CD27 and Alzheimer disease: This remodeling is characterized by an increase of double-negative (IgD-CD27-) memory B cells, a marked reduction in naïve B cells (IgD+ CD27−), and an upregulation of receptors for pro-inflammatory cytokines.22,23 Within the AD brain, B lymphocytes are found to be adjacent to Aβ plaques24 and IgG-immunopositive neurons.25 Although the above evidence suggests that the peripheral immune system is implicated in AD pathogenesis, much remains to be desired with regards to the origin and types of peripheral immune cells and the relevant mechanisms in the early stage of AD.