In a meta-analysis of cytokines in AD, circulating (blood) concentrations of tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, IL-1β, IL-6, IL-12 and IL-18 were increased in AD patients whereas in CSF, only TGF-β was elevated [12]. This evidence concerns the gene TGFB1 and Alzheimer disease.