CD4 and Alzheimer disease: We have recently reported parenchymal infiltration of T helper (Th)17 cells, a subpopulation of proinflammatory CD4+ T cells, via a disrupted blood-brain barrier (BBB) and elevation of the Th17 proinflammatory cytokines, interleukin (IL)-17 and IL-22 in amyloid-β (Aβ)1–42-induced AD brain [8].